- /af"ri keuh/, n.1. a continent S of Europe and between the Atlantic and Indian oceans. 551,000,000; ab. 11,700,000 sq. mi. (30,303,000 sq. km).adj.2. African.
* * *ISecond largest continent on Earth.It is bounded by the Mediterranean Sea, the Atlantic Ocean, the Red Sea, and the Indian Ocean and is divided almost equally by the Equator. Area: 11,717,370 sq mi (30,348,110 sq km). Population (2001 est.): 816,524,000. Africa is composed largely of a rigid platform of ancient rocks that underlies vast plateau regions in the interior. Its average elevation is about 2,200 ft (670 m), but elevations range from 19,340 ft (5,895 m) at Mount Kilimanjaro to 515 ft (157 m) below sea level at Lake Assal. The Sahara, the world's largest contiguous desert, occupies more than one-fourth of the total land area. The continent's hydrology is dominated by the Nile River in the north, the Niger River in the west, and the Congo River in central Africa. Less than one-tenth of the land area is arable, while nearly one-fourth is forested or wooded. The peoples of Africa probably speak more languages than those of any other continent. Arabic is predominant from Egypt to Mauritania and in The Sudan. Northern Africans speak a family of languages known as Afro-Asiatic. The vast majority of sub-Saharan peoples speak Bantu languages of the Niger-Congo family, while smaller numbers in central Africa speak Nilo-Saharan languages and in southern Africa Khoisan languages. Peoples of European descent are found mostly in the south; Dutch (Boer) migrations began in the 17th century, and the English first settled in what is now Kenya and Zimbabwe in the 19th century. Africa as a whole is a developing region. Agriculture is the key sector of the economy in most countries. Diamond and gold mining are especially important in the south, while petroleum and natural gas are produced particularly in the west. Most African governments are controlled by the military or a single party. Many legal systems combine laws introduced by European powers during the colonial era with traditional law, though North African countries derive many laws from Islam. African leaders have sought to develop a pan-African approach to the continent's political and military affairs through the Organization of African Unity and its successor, the African Union. Africa is widely recognized as the birthplace of humankind. Archaeological evidence indicates that the continent has been inhabited by humans and their hominid forebears for some 4,000,000 years or more. Anatomically modern humans are believed to have appeared about 100,000 years ago in the eastern region of sub-Saharan Africa. Somewhat later these early humans spread into northern Africa and the Middle East and, ultimately, to the rest of the world. Africa's first great historical kingdom, Egypt, arose along the Nile с 3000 BC and flourished for nearly 3,000 years. The Phoenicians established a colony at Carthage and controlled the western Mediterranean for nearly 600 years. While northern Africa was dominated by the Romans for several centuries, the first known empire in western Africa was Ghana (5th–11th century AD). Muslim empires included those of Mali (с 1250–1400) and Songhai (с 1400–1591). In eastern and central Africa the emphasis was on trade with Arabia, and several powerful city-states, including Mogadishu and Mombasa, were established. The Portuguese explored the western coast in the 15th century. Before the late 19th century, Europe showed little interest in colonizing Africa, but by 1884 European countries had begun a scramble to partition the continent, and by 1920 much of it was under colonial rule. Anticolonial sentiment developed gradually, becoming widespread after 1950, and one by one the colonies became independent, the last in 1990. Political instability, refugee problems, famine, and AIDS are the chief problems facing the continent at the start of the 21st century.II(as used in expressions)Africa RomanSouth Africa Republic ofSouth West Africa People's Organization
* * *Introductionthe second largest continent, after Asia, covering about one-fifth of the total land surface of the Earth. The continent is bounded on the west by the Atlantic Ocean, on the north by the Mediterranean Sea, on the east by the Red Sea and the Indian Ocean, and on the south by the mingling waters of the Atlantic and Indian oceans.Africa's total land area is approximately 11,724,000 square miles (30,365,000 square km), and the continent measures about 5,000 miles (8,000 km) from north to south and about 4,600 miles (7,400 km) from east to west. Its northern extremity is Al-Ghīrān Point, near Al-Abyaḍ Point (Cape Blanc), Tunisia; its southern extremity is Cape Agulhas, South Africa; its farthest point east is Xaafuun (Hafun) Point, near Cape Gwardafuy (Guardafui), Somalia; and its western extremity is Almadi Point (Pointe des Almadies), on Cape Verde (Cap Vert), Senegal. In the northeast, Africa was joined to Asia by the Sinai Peninsula until the construction of the Suez Canal. Paradoxically, the coastline of Africa—18,950 miles (30,500 km) in length—is shorter than that of Europe, because there are few inlets and few large bays or gulfs.Off the coasts of Africa a number of islands are associated with the continent. Of these Madagascar, one of the largest islands in the world, is the most significant. Other smaller islands include the Seychelles, Socotra, and other islands to the east; the Comoros, Mauritius, Réunion, and other islands to the southeast; Ascension, St. Helena (Saint Helena), and Tristan da Cunha to the southwest; Cape Verde, the Bijagós Islands (Bijagós Islands), Bioko, and São Tomé and Príncipe to the west; and the Azores and the Madeira (Madeira Islands) and Canary (Canary Islands) islands to the northwest.The continent is cut almost equally in two by the Equator, so that most of Africa lies within the tropical region, bounded on the north by the Tropic of Cancer and on the south by the Tropic of Capricorn. Because of the bulge formed by western Africa, the greater part of Africa's territory lies north of the Equator. Africa is crossed from north to south by the prime meridian (0° longitude), which passes a short distance to the east of Accra, Ghana.In antiquity the Greeks are said to have called the continent Libya and the Romans to have called it Africa, perhaps from the Latin aprica (“sunny”) or the Greek aphrike (“without cold”). The name Africa, however, was chiefly applied to the northern coast of the continent, which was, in effect, regarded as a southern extension of Europe. The Romans, who for a time ruled the North African coast, are also said to have called the area south of their settlements Afriga, or the Land of the Afrigs—the name of a Berber community south of Carthage.The whole of Africa can be considered as a vast plateau rising steeply from narrow coastal strips and consisting of ancient crystalline rocks. The plateau's surface is higher in the southeast and tilts downward toward the northeast. In general the plateau may be divided into a southeastern portion and a northwestern portion. The northwestern part, which includes the Sahara (desert) and that part of North Africa known as the Maghrib, has two mountainous regions—the Atlas Mountains in northwestern Africa, which are believed to be part of a system that extends into southern Europe, and the Ahaggar (Hoggar) Mountains in the Sahara. The southeastern part of the plateau includes the Ethiopian Plateau, the East African Plateau, and—in eastern South Africa, where the plateau edge falls downward in a scarp—the Drakensberg range. One of the most remarkable features in the geologic structure of Africa is the East African Rift System, which lies between 30° and 40° E. The rift itself begins northeast of the continent's limits and extends southward from the Ethiopian Red Sea coast to the Zambezi River basin.Africa contains an enormous wealth of mineral resources, including some of the world's largest reserves of fossil fuels, metallic ores, and gems and precious metals. This richness is matched by a great diversity of biological resources that includes the intensely lush equatorial rainforests of Central Africa and the world-famous populations of wildlife of the eastern and southern portions of the continent. Although agriculture (primarily subsistence) still dominates the economies of most African countries, the exploitation of these resources has become the most significant economic activity in Africa in the 20th century.Climatic and other factors have exerted considerable influence on the patterns of human settlement in Africa. While some areas appear to have been inhabited more or less continuously since the dawn of humanity, enormous regions—notably the desert areas of northern and southwestern Africa—have been largely unoccupied for prolonged periods of time. Thus, although Africa is the second largest continent, it contains only about 10 percent of the world's population and can be said to be underpopulated. The greater part of the continent has long been inhabited by black peoples, but in historic times there also have occurred major immigrations from both Asia and Europe. Of all foreign settlements in Africa, that of the Arabs has made the greatest impact. The Islamic religion, which the Arabs carried with them, spread from North Africa into many areas south of the Sahara, so that many western African peoples are now largely Islamized.Davidson S.H.W. Nicol Ed.This article treats the physical and human geography of Africa, followed by discussion of geographic features of special interest. For discussion of individual countries of the continent, see the articles Egypt, Madagascar, and Sudan, The. African regions are treated under the titles Central Africa, eastern Africa, North Africa, Southern Africa, and Western Africa; these articles also contain the principal treatment of African historical and cultural development. For discussion of major cities of the continent, see the articles Alexandria, Cairo, Cape Town, Johannesburg, and Kinshasa. Related topics are discussed in the articles African literature; South African literature; architecture, African (African architecture); art, African; dance, African (African dance); music, African (African music); theatre, African; art and architecture, Egyptian; Islam (Islām); arts, Islamic (Islamic arts); and Islamic world (Islāmic world). For further references, see also the Index.Geologic historyGeneral considerationsThe African continent essentially consists of five ancient Precambrian cratons (Kaapvaal, Zimbabwe, Tanzania, Congo, and West African) that were formed between about 3.6 and 2.0 billion years ago and that basically have been tectonically stable since that time; these cratons are bounded by younger fold belts formed between 2.0 billion and 300 million years ago. All these rocks have been extensively folded and metamorphosed (that is, they have been modified in composition and structure by heat and pressure). Precambrian rock outcrops appear on some 57 percent of the continent's surface, while the rest of the surface consists of largely undeformed younger sediments and volcanic rocks.The oldest rocks are of Archean (Archean Eon) age (more than 3.6 to 2.5 billion years old) and are found in the so-called granite-gneiss-greenstone terrains of the Kaapvaal, Zimbabwe, and Congo cratons. They consist of gray, banded gneisses, various granitoids, and rather well-preserved volcanic rocks that show evidence of submarine extrusion (i.e., emission of rock material in molten form) and formation under high temperatures. The rock type komatiite is particularly diagnostic of these volcanic sequences and is almost exclusively restricted to the Archean Eon. The cratons were tectonically stabilized by voluminous granite intrusions toward the end of the Archean and were then covered by clastic sediments, some of which contain economically important gold and uranium deposits (e.g., the Witwatersrand System in South Africa).The Proterozoic Eon (2.5 billion to 570 million years ago) is characterized by the formation of several mobile belts, which are long, narrow zones of strongly deformed and metamorphosed rocks that occur between the cratons and probably resulted from the collision between the cratons due to plate tectonic processes. The oldest mobile belts are found in Archean rocks, such as the Limpopo belt separating the Kaapvaal from the Zimbabwe craton. Younger belts were formed during a continentwide thermotectonic event known as the Eburnian (2.2 to 1.8 billion years ago), which gave rise to the Birimian assemblage in western Africa, the Ubendian assemblage in east-central Africa, and large volumes of rocks in Angola. Still younger belts of the Kibaran thermotectonic event (1.2 billion to 950 million years ago) are found in eastern and southern Africa.The end of the Precambrian was marked by a major event of mobile-belt formation known as the Pan-African episode (c. 950 to 550 million years ago), which generated long fold belts, such as the Mozambique belt along the east coast of Africa, the Damara and Katanga belts extending from Namibia into Congo (Kinshasa) and Zambia, the West Congo belt between Angola and Gabon, the Dahomey-Ahaggar belt between Ghana and Algeria, and the Mauritanide belt from Senegal to Morocco.A unique late Precambrian evolution is recorded in the so-called Arabian-Nubian Shield of northeastern Africa and Arabia. There, large volumes of volcanic and granitoid rocks were generated in an island-arc, marginal-basin setting—an environment similar to that of the present southwestern Pacific Ocean. Rocks were accreted onto the ancient African continent, the margin of which was then near the present Nile River, by subduction processes identical to those observed today. (Subduction involves the descent of the edge of one lithospheric plate beneath that of another where two such plates collide.)The interiors of the ancient cratons were not affected by the above tectonic events, and intracratonic sedimentary and volcanic sequences accumulated in large basins. The most important of these are the Transvaal basin on the Kaapvaal craton that contains economically important iron ore deposits; the Congo basin; and the West African basin, with its thick late-Proterozoic sediments including a prominent tillite horizon that marks a major glaciation event at the end of the Precambrian.After the Precambrian, Africa's geologic history is characterized by the following events: the formation of fold belts in the Paleozoic Era (570 to 245 million years ago) in South Africa (the Cape fold belt), Morocco (the Anti-Atlas belt), and Mauritania (the Mauritanide belt) bordering the older cratons; voluminous basaltic volcanism some 230 to 200 million years ago in South Africa, Namibia, and East Africa, known as the Karoo System, that was probably related to the beginning of the breakup of the Gondwana supercontinent; the formation of a young mountain belt in northwestern Africa some 100 to 40 million years ago as a result of collision between the African and European plates, together with the closure of the ancestral Mediterranean Sea (the Tethys Sea); and the development of the East African Rift System during and after the Tertiary Period (i.e., the last 66.4 million years), leading to the opening of the Red Sea, the northeast drift of the Arabian Plate, and the fracturing of the ancient crust of Africa along several long rift valleys, accompanied by extensive volcanism.Rock types and structural evolutionThe Precambrian (Precambrian time)The oldest rocks consist of gneisses, granites, metasediments, and metavolcanic rocks 3.6 to 2.5 billion years old; all are variably deformed and metamorphosed to some degree. The best-preserved assemblages occur in the Kaapvaal and Zimbabwe cratons and contain large deposits of gold and sulfide minerals. The volcanic suites are dominated by basaltic and komatiitic lavas, often interlayered with metasediments and generally referred to as greenstone belts. These are often found together with layered gneisses, or they are intruded by granitoid plutons. Several generations of greenstones have been recognized. The oldest formed about 3.4 billion years ago, the second some 3.0 to 2.9 billion years ago, and the third some 2.7 to 2.6 billion years ago. Some of the oldest traces of life are preserved as unicellular algae in Precambrian cherts of the Barberton greenstone belt in the Transvaal region of South Africa. The end of the Archean is marked by voluminous granite intrusions, after which Africa's cratons became tectonically stable. One of the most spectacular features marking the end of the Archean is the intrusion of the Great Dyke in Zimbabwe, a large, layered body of mafic-ultramafic rocks with substantial deposits of chromium, asbestos, and nickel. It is still not clear whether Archean evolution was characterized by the same plate tectonic processes that are seen today, and there are suggestions that the greenstone belts are remnants of ancient oceanic crust. Cratonic (essentially undeformed) sediments appear in the stratigraphic record for the first time in the late Archean and are best developed in the Kaapvaal craton of southern Africa.The early Proterozoic (2.5 to 1.6 billion years ago) is characterized by cratonic clastic sediments on the stable cratons—the best examples are the Witwatersrand-Ventersdorp-Transvaal basin of southern Africa and the Francevillian basin in Gabon—and by metavolcanic-metasedimentary rocks and granitoids in noncratonic areas such as the extensive Birimian terrain of western Africa extending from Senegal to Ghana. Of particular interest are extensive stromatolite-bearing limestones and economically important iron formations in the Transvaal sequence of South Africa that provide evidence for an oxygen-rich atmosphere by about 2.2 billion years ago. About 2 billion years ago the Bushveld Complex—which is one of the largest differentiated igneous bodies on Earth, containing major deposits of platinum, chromium, and vanadium—was emplaced in the northern Kaapvaal craton. The middle part of the early Proterozoic was dominated by powerful orogenic (mountain-building) processes that gave rise to fold belts in which sedimentary and volcanic rocks originally deposited in deep basins along the continental margins were severely deformed, metamorphosed, intruded by granitoid plutons, and finally uplifted into mountain ranges, probably as a result of continental collision. This Eburnian event was particularly active in western Africa, where it deformed the Birimian assemblages; but it was also active in eastern Africa, where it generated the Ubendian belt in southern Tanzania, and in southwestern Africa, where it formed major rock units in Angola and northern Namibia. By the end of the early Proterozoic, the Archean crustal blocks had grown into cratons of considerable size.The record of the middle Proterozoic (1.6 billion to 900 million years ago) shows deposition of continental sediments and volcanic rocks on the cratons and adjacent to the earlier fold belts (molasse deposits). Undeformed or only mildly folded successions are found in southern Africa (Waterberg and Matsap sequences), in northern Zambia, and in Congo (Kinshasa). Elsewhere, sedimentary and volcanic sequences were deposited in elongate basins that were later subjected to intense deformation and metamorphism during the Kibaran event. This important thermotectonic episode gave rise to the Kibaran-Burundian fold belt in east-central Africa, the Ruwenzori belt in Uganda, and the Namaqua-Natal belt in South Africa and Namibia.The late Proterozoic (900 to 570 million years ago) is again characterized by platform deposits in stable areas, such as the West African craton (Taoudeni and Tindouf basins), the Congo craton, the Kalahari craton (Nama basin of Namibia), and the Tanzania craton (Bukoban beds). Tectonic and magmatic activity was concentrated in mobile belts surrounding these stable areas and took place throughout the late Proterozoic, during the so-called Pan-African thermotectonic event. Long, linear belts—such as the Damara-Katanga of central and southwestern Africa, the Mozambique belt of eastern Africa, and the Dahomey-Ahaggar belt of western Africa—formed during this time, and some of these belts contain diagnostic rock assemblages that indicate that they resulted from continental collisions. Many late Precambrian sequences of Africa contain one or two beds of tillites (sedimentary rocks that are composed of lithified clay and rock sediments produced by the action of ice), which are thought to have resulted from an extensive glaciation that covered much of Africa at this time. In the Arabian (Eastern) Desert of Egypt and in the Red Sea Hills of The Sudan, a predominance of volcanic rocks and granitoids, together with frequent remnants of ancient oceanic crust, document an evolution similar to what is now occurring in the island-arc systems of the southwestern Pacific. These rocks clearly demonstrate that plate tectonic processes operated in the late Precambrian.The Paleozoic EraThe Paleozoic Era consists of the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian periods and includes two major mountain-building episodes. The continent of Africa may be said to have taken shape during the Paleozoic. A glacial period during the Ordovician is evidenced by widespread deposition tillites (tillite), which may be seen in southern Morocco, throughout western Africa, and in subequatorial Africa as far south as Namibia. This tillite sequence marks the transition from the end of the Precambrian to the beginning of the Cambrian Period.Marine fossils of the Cambrian Period (570 to 505 million years ago) are found in southern Morocco, the Western and Mauritanian Sahara, and Namibia. In Egypt and in the Arabian (Arabia) Peninsula, their presence has been revealed by drilling. Elsewhere, they remain unknown.During the Ordovician Period (505 to 438 million years ago), fossiliferous marine sandstone completely covered northern and western Africa, including the Sahara. The Table Mountain sandstone of South Africa constitutes its only other trace. This period is, in addition, remarkable for broad, large-scale deformation of the African crust, which raised the continental table of the central and western Sahara by approximately 5,000 feet (1,500 metres). Each emergence resulted in the creation of valleys that became flooded when the continent subsided. Toward the end of the period, the Sahara became glaciated, and tillites and sandstones filled the valleys. A complete change of sedimentation characterized the Silurian Period (438 to 408 million years ago); this is indicated by the deposits of graptolitic shales (those containing small fossil colonies of extinct marine animals of uncertain zoological affinity) in the Arabian Peninsula and in northwestern Africa.Marine fossils of the Devonian Period (408 to 360 million years ago) are found in North Africa and in the Sahara. Traces also have been discovered in parts of Guinea, Ghana, and Arabia, as well as in Gabon; they also occur in the Bokkeveld Series of South Africa. Fossilized plants that include Archaeosigillaria (ancient club mosses) may be traced in formations of the earlier Devonian Period in the Sahara and in South Africa (Witteberg Series).The Carboniferous Period (360 to 286 million years ago) was marked by the onset of several major tectonic events. Evidence of marine life that existed in the earlier part of this period comes from fossils found in North Africa, the central and western Sahara, and Egypt. During the middle and later parts of the Carboniferous, the Hercynian mountain-building episodes occurred as a result of collision between the North American and African plates. The Mauritanide mountain chain was compressed and folded at this time along the western margin of the West African craton from Morocco to Senegal. Elsewhere, major uplift or subsidence occurred, continuing until the end of the Triassic Period (i.e., about 208 million years ago). These structures were synformal (folded with the strata dipping inward toward a central axis) in the Tindouf and Taoudeni basins of western Algeria, Mauritania, and Mali and antiformal (forming a mountainous spine or dome) at Reguibat in eastern Western Sahara.The Late Carboniferous Period is represented throughout the Sahara by layers of fossilized plants and sometimes—as in Morocco and Algeria—by seams of coal. Different phenomena may be observed, however, in the region of subequatorial Africa, including the Dwyka tillite, which covers part of South Africa, Namibia, Madagascar, an extensive portion of the Congo Basin, and Gabon. At several places in South Africa, these Dwyka strata are covered by thin marine layers that serve to demarcate the transition from the Carboniferous to the Permian Period and that form the beginning of the great Karoo System.Marine fossils of the Permian Period (286 to 245 million years ago) are visible in southern Tunisia, in Egypt, in the Arabian Peninsula, on the coasts of Tanzania, and in the Mozambique Channel. Elsewhere, traces of the Permian are of continental rather than marine origin and are included in the Karoo System in South Africa. There, the Lower Permian strata are known as the Ecca Series and are divided into three groups: the Lower Ecca (containing almost 1,000 feet of shales), the Middle Ecca (some 1,650 feet of sandstone, seams of coal, and fossilized plants), and the Upper Ecca (about 650 feet of shales again).The Upper Permian is represented by the lower part of the Beaufort Series, which continued forming into the Early Triassic Period. The Beaufort Series is almost 10,000 feet thick and is famous for its amphibian and reptile fossils; a similar series is also found in the southern Soviet Union. Other Permian formations, not as rich in coal, occur in Congo (Kinshasa), Tanzania, Kenya, Uganda, Zambia, Zimbabwe, Mozambique, and Madagascar.The absence of primary marine formations throughout southern Africa should be emphasized. It is not yet known whether this absence is due to a hiatus in deposition or to erosion.The Mesozoic EraThe Mesozoic Era (245 to 66.4 million years ago) is divided into three periods—the Triassic, Jurassic, and Cretaceous—and is remarkable for the transgression of ancient seas and for the emergence of massive land formations containing interesting fossil remains.Marine formationsDuring the Triassic Period (245 to 208 million years ago), ancient seas left deposits of marine formations in North Africa, the southern Sahara, Egypt, Arabia, and parts of Tanzania and northern Madagascar. Deposits from the Jurassic Period (208 to 144 million years ago) extend to the Atlantic basins of the Río de Oro region of Western Sahara and Senegal along the northwest coast of the continent. In the middle of the Jurassic a great transgression of the Indian Ocean extended over Somalia and much of Ethiopia. In the Cretaceous Period (144 to 66.4 million years ago) this was followed by a series of marine transgressions, including those along the coasts of equatorial Africa when Gondwana broke up and the present Atlantic and Indian oceans took shape; during one transgression a shallow sea covered much of the northern and central Sahara and Egypt as far south as The Sudan; and a later one again covered the same areas, as well as western Arabia and the west coast of Madagascar.Continental formationsIn Africa north of the equator and in Arabia, Mesozoic continental formations covered large areas. During the Triassic the Saharan Zarzaitine Series, containing dinosaur and other reptilian fossil remains, was deposited. The Saharan Taouratine Series, containing fossils of vegetation and of great reptiles, was laid down during the Jurassic. In the upper Karoo System of subequatorial Africa, formed during the Early Triassic Period, the Beaufort Series contains fossils of fish, amphibians, and reptiles. The final stages of the Triassic and the Early Jurassic periods were characterized by the terminal folding of the Cape mountain chain, by subsidence in the Karoo basin, by fracturing, and by widespread upwelling of Karoo basaltic lavas through fissures, creating formations some 4,000 feet thick, such as the Drakensberg range along the eastern border of Lesotho and in South Africa.During the Jurassic and the Cretaceous periods, widespread sediments were deposited that contain fossilized plants, dinosaurs, and smaller reptiles. Certain unique eruptions occurred during the Cretaceous that led to the creation of kimberlite pipes (near-cylindrical rock bodies, usually approximately vertical and derived from melting at great depth in the upper mantle) in southern and central Africa; some of these, particularly in South Africa, Botswana, Namibia, Angola, and Congo (Kinshasa), contain large quantities of diamonds and are the main source of this precious mineral.The Cenozoic EraThe Cenozoic, the most recent major interval of geologic time (from 66.4 million years ago to the present), is commonly divided into two periods: the Tertiary and the Quaternary. The Tertiary Period (66.4 to 1.6 million years ago) is remarkable for its great tectonic movements, that resulted in the Alpine orogeny. During this mountain-building episode, the Atlas Mountains of northwestern Africa were folded and uplifted. Notable too are the formation of the Red Sea Rift valley and the volcanism and rifting that took place during the later stages of the period.Marine formationsThe initial epoch of the Tertiary, the Paleocene (Paleocene Epoch) (66.4 to 57.8 million years ago), is important for its marine formations with animal fossils, including nummulites (a large kind of foraminifera, which are unicellular animals of macroscopic size), nautiloids (shelled cephalopods, which are mollusks with tentacles attached to their heads), and echinoids (sea urchins); all of these are found in North and West Africa and in the Sahara. With the exception of the Sahara, nummulites of the Eocene Epoch (57.8 to 36.6 million years ago) are found in the same places, as well as on the African coasts of the Indian Ocean. There also are lepidocyclines (foraminifera) of the Oligocene Epoch (36.6 to 23.7 million years ago) and of the Miocene Epoch (23.7 to 5.3 million years ago).Continental formationsSeveral levels may sometimes be distinguished in the continental formations of the Tertiary Period. They include lower Eocene levels containing Pseudoceratodes (a genus of gastropod) and Dyrosaurus (a type of reptile), as well as upper Eocene and Oligocene levels containing silicified wood and fossilized fish, turtles, crocodiles, snakes, and mammals. In Egypt the Oligocene deposits found in the Al-Fayyūm (Fayyūm, Al-) area contain mammals, birds, turtles, and crocodiles. Sediments of the Lower Miocene (Miocene Epoch), which are found on the banks of Lakes Rudolf and Victoria in East Africa, contain mastodon (a large elephant-like mammal) and Proconsul africanus (a large ape). Central Asian hipparions (three-toed ancestors of the horse), which simultaneously entered Africa and Europe during the Late Miocene Epoch (11.2 to 5.3 million years ago), also left their fossilized remains in this region, as did genera of hominoid (manlike) apes—e.g., Kenyapithecus of Kenya—at about the same time.The first major folding of the Tell Atlas Mountains of North Africa took place in the Oligocene Epoch. In the Miocene, North African flysch (thick and extensive deposits composed largely of sandstone) formed layers that, from the Er-Rif to northern Tunisia, were pushed from the north toward the south. The High Plains area, farther south, which as a whole was only mildly deformed, was bounded on the south by the northern Atlas Mountains, which intervened between it and the Saharan Atlas. Continental movements lifted the Aurès mountains to a height of about 3,300 feet during the middle of the Miocene; the Aurès are bounded on the south by the northern Sahara structural line, which extends from Agadir in Morocco in the west to the Gulf of Gabes in Tunisia in the east, dividing the African Shield from the folded Mediterranean, or Alpine, zone.Formation of the Red SeaTectonic movements in the region of the Arabian-Nubian Shield that took place at the end of the Oligocene and the beginning of the Miocene Epoch almost separated Arabia from Africa. A trough (fault-bounded depression) developed because of divergence in the crust between northeastern Africa and western Arabia, and the Mediterranean Sea swept into the resulting rift valley, forming a gulf that extended to Yemen. The gulf was prevented from joining the Indian Ocean only by an isthmus that stretched from Djibouti in the west to Aden in the east.At the end of the Miocene the Isthmus of Suez was formed, and the gulf became a saline lake at the bottom of which thick evaporites (sediments formed as a result of evaporation) were laid down. The isthmus permitted Asian animal life to pass into Africa during part of the Pliocene Epoch (5.3 to 1.6 million years ago). Subsidence of the Djibouti-Aden isthmus, also during the Pliocene, permitted the Indian Ocean to flow into the Red Sea as far as the Isthmus of Suez.Volcanism and riftingTectonic movements during the Miocene and Pliocene scored the African continent with a network of faults that generally trended northeast to southwest and northwest to southeast. Volcanic eruptions and basaltic upwellings accompanied fracturing in the Ahaggar area of southern Algeria, in the Tibesti area of Libya and Chad, in Ethiopia, throughout East Africa, and in Cameroon, as well as in the islands of Bioko (formerly Fernando Po) and São Tomé and Príncipe in the Gulf of Guinea.Pleistocene and Holocene developmentsThe Quaternary Period (Quaternary) is divided into the Pleistocene Epoch (1,600,000 to 10,000 years ago) and the Holocene, or Recent, Epoch (the past 10,000 years). It represents a phase of continuing volcanic activity that caused the basement rocks of the Ahaggar and Tibesti mountains of the central Sahara to rise. The activity manifested itself in eruptions, in the deepening of the Saharan valleys, and in the extrusion of flood basalt.During the cold humid periods called pluvials, which correspond to the glacial phases of the Northern Hemisphere, the glaciers that covered the high mountains of East Africa were from 3,000 to 5,000 feet thicker than those remaining in the summit zones today. Elsewhere, the desert zones of the Sahara and the Kalahari were alternately subjected first to humid and then to dry and arid phases that expanded the desert surface at the expense of adjacent forested zones.The oldest levels at which hominid (Hominidae) remains have been found are known as the Villafranchian-Kaguerian Series and are recognized in Africa in Ethiopia and Kenya. These levels date to approximately three to four million years ago and contain fossils of the genus Australopithecus. The Kaguerian-Kamasian Interpluvial levels, which date to about 500,000 years ago, contain the remains of Homo erectus at Olduvai Gorge (Tanzania) and in Morocco, Algeria, and Chad.The Kamasian, or Second, Pluvial of the Middle Pleistocene Epoch (900,000 to 130,000 years ago) corresponds to the Mindel in Europe. A dry but not a desert climate is implied by the Kamasian-Kanjeran Interpluvial levels at Olduvai Gorge. The Kanjeran, or Third, Pluvial occurred during the Middle Pleistocene and corresponds to the Riss Pluvial in Europe.An arid phase, which greatly reduced forest land, is revealed in the Kanjeran-Gamblian Interpluvial levels, lasting from about 60,000 to 55,000 years ago. This period corresponds to an important tectonic phase marked by uplift and subsidence in North Africa and activity along all the faults, in particular those in eastern Africa. It was at this time that eastern Africa assumed its present topographic character.During the Gamblian, or Fourth, Pluvial, which occurred from approximately 30,000 to 15,000 years ago, three distinct humid phases are separated by drier intervals. During these phases the dimensions of Lake Chad (Chad, Lake) and those of the glaciers of Mount Kenya (Kenya, Mount) and of Kilimanjaro diminished rapidly. The postpluvial phase that followed this period, equivalent to the postglacial phase of the Northern Hemisphere, was marked by a succession of alternating dry and humid stages and by the desertification of both the Sahara and the Kalahari, a process that began about 3,000 BC.Alfred KrönerThe landReliefThe physiography of Africa is essentially a reflection of the geologic history and geology that is described in the previous section. The continent, composed largely of a vast rigid block of ancient rocks, has geologically young mountains at its extremities in the highlands of the Atlas Mountains in the northwest and the Cape ranges in the south. Between these mountainous areas is a series of plateau surfaces, with huge areas that are level or slightly undulating, above which stand occasional harder and more resistant rock masses. Surrounding these surfaces is a zone of plateau slopes below which are narrow coastal belts widening along the Mediterranean coast, the coastlands of Tanzania and Mozambique, a narrow belt between the Niger and Cunene (Kunene) rivers, and an area northward of the Gambia and Sénégal rivers.Kilimanjaro (19,340 feet [5,895 metres]) is the highest point on the continent; the lowest is Lake Assal (Assal, Lake) (515 feet [157 metres] below sea level) in Djibouti. In proportion to its size, Africa has fewer high mountains and fewer lowland plains than any other continent. The limited areas above 8,000 feet are either volcanic peaks or resistant massifs. All the land below 500 feet occurs within 500 miles of the coast, except for two small basins in the Sahara.The higher areas of the south and east are in marked contrast to the considerably lower elevation of the western and northern parts of the continent. South of a line drawn from near the mouth of the Congo River to the Gulf of Aden, most of the land lies 1,000 feet or more above sea level, and much of it exceeds 3,000 and even 4,000 feet. North of the line there is relatively little land above 3,000 feet, most of the area being between 500 and 1,000 feet above sea level; there are also broad coastal lowlands, except in the region of the Atlas Mountains and, in the east, beyond the Nile.The highest extensive areas are to be found in Ethiopia, parts of which exceed 15,000 feet. Southward the East African Plateau is highest in Kenya, where it is often 8,000 feet or more above sea level; there are occasional volcanic peaks that are much higher, such as Kilimanjaro, Mount Kenya (Kenya, Mount) (17,058 feet), Meru (Meru, Mount) (14,978 feet), and Elgon (Elgon, Mount) (14,178 feet). The Ruwenzori (Rwenzori) Range—sometimes called the Mountains of the Moon (Ruwenzori Range)—which reaches its highest elevation at Margherita Peak (16,795 feet) on the borders of Congo (Kinshasa) and Uganda, is not volcanic in origin. From East Africa the plateau extends southward, often with a well-defined, though not continuous, escarpment particularly noticeable in the Drakensberg of southern Africa, where Ntlenyana (Thabana Ntlenyana), or Ntshonyana, is 11,424 feet and Mont-aux-Sources is 10,823 feet. There, the plateau edges are especially marked, because the rock formations are hard and horizontal, whereas in Ethiopia they are conspicuous because of faulting. Where the rocks are softer and less resistant, the escarpment is not so pronounced and so forms less of a barrier to climatic influences and to human movement.To the north and west of the plateau area of the southern parts of the continent there is a general descent to the lower areas of the basins of the Congo, Niger, and Nile rivers. The only large areas that extend above 3,000 feet are in the folded ranges of the Atlas Mountains and in the central Sahara, where resistant granites form the massifs of Ahaggar and Tibesti. The interior uplands of West Africa and of Cameroon consist of ancient crystalline rocks, reaching considerable heights only in the Fouta Djallon plateau in Guinea, in the Guinea Highlands, which also extend over the borders of Sierra Leone and Liberia, in the Jos Plateau in Nigeria, in the Adamawa (Adamawa Plateau) region of Nigeria and Cameroon, and in the Cameroon Highlands. There are extensive low-lying areas near the coast and in the basins of the Sénégal, Gambia, Volta, and Niger–Benue rivers. The high areas of Darfur in The Sudan (more than 10,000 feet) and of Mount Cameroon (Cameroon, Mount) (13,435 feet) are volcanic in origin and are evidence of the same tensions that have resulted in rifting and volcanism in East Africa.The East African Rift System constitutes the most striking and distinctive relief feature of the continent. Associated with its formation was the volcanic activity responsible for most of the higher peaks of East Africa, including Kilimanjaro. Seismic and volcanic disturbances are still recorded in the western portions of the rift valley system. In the Virunga Mountains, northeast of Lake Kivu (Kivu, Lake), there are periodic outbursts (about every 10 or 12 years) that have created a series of lava flows. One of these volcanoes dammed the rift valley and converted a large area, formerly drained by a tributary of the Nile, into Lake Kivu.The rift valley extends for about 4,000 miles, its course being clearly marked by many of the lakes of East Africa (East African lakes) as well as by the adjacent volcanic peaks. From the Gulf of Aqaba it can be traced southward along the Red Sea and into the Ethiopian Plateau to Lakes Rudolf, Naivasha, and Magadi in Kenya. Farther south, through Tanzania, the line of the rift is not quite so obvious. The walls that constitute the eastern rim have been more easily eroded, while the lakes of this area are generally smaller and not in line, and some of them are only waterless salt beds. The largest of these lakes are Natron (Natron, Lake) and Manyara (Manyara, Lake), with Eyasi in a side branch of the main rift. The edges are obvious enough to the south in Malaŵi, where a huge crusted block collapsed along the parallel faults that constitute the steeply rising slopes of Lake Nyasa (Nyasa, Lake) (Malaŵi). The lake is 360 miles long but never more than 50 miles wide; it has a maximum depth of 2,310 feet. The rift then follows the line of the Shire Valley to reach the Indian Ocean near Beira, Mozambique.The western branch, or Western Rift Valley, extends from the northern end of Lake Nyasa in a great arc, taking in Lakes Rukwa, Tanganyika (after Lake Baikal in Siberia the deepest lake in the world), Kivu, Edward, and Albert. Subsidiary branches of this valley include the basins in which lie Lakes Mweru and Upemba.Most of the lakes that occur along the course of the rift valley lie well below the general level of the plateau, ranging from about 1,300 to 3,000 feet above sea level. They are generally very deep and bear a striking resemblance to fjords; some have floors that are below sea level, even though their surfaces are hundreds of feet above sea level.In complete contrast is Lake Victoria (Victoria, Lake), the largest of all African lakes, which occupies a shallow depression on a plateau 3,720 feet above sea level between the major branches of the rift valley. Its greatest depth is only 270 feet, but, with an area of 26,828 square miles, it is the third largest of the world's lakes, after the Caspian Sea and Lake Superior.See individual articles for a detailed discussion of the Atlas Mountains, East African mountains, Ituri Forest, Kalahari, Namib, Sahara, and veld.Robert Walter SteelDrainageThe uplifting and warping of the surface of the African continent that occurred during the Pliocene and Pleistocene epochs produced a number of structural basins; these are now either individually occupied by, or are linked up with, drainage systems. With the exception of the Chad basin, all the major drainage basins have outlets to the sea. In addition, minor drainage basins, similar to that of Lake Chad (Chad, Lake), are situated in the East African Rift Valley. Some, again like Lake Chad, constitute the focus of centripetal drainage (drainage directed toward the centre), while others are linked to river systems. Although the East African lakes are climatically and economically important, relatively little is known of their hydrological characteristics.Climate, geology, and the history of tectonic activity have imparted certain common characteristics to African rivers. Spatial variations in the incidence and amount of rainfall are reflected in their hydrological regimes. In areas that have one rainfall season, for example, and have pronounced drought throughout the rest of the year, the rivers flood in the rainy season and shrink in the dry season.Whatever their hydrological regimes, all the important African rivers are interrupted by rapids, cataracts, and waterfalls. This is explained by several factors, the most important of which is the past tectonic activity, or regional land movements, that caused ridges to be formed across the courses of the major rivers. Waterfalls (waterfall) are often found where the rivers are still engaged in cutting downward as they flow across these ridges; Cahora Bassa (falls) on the Zambezi and the Augrabies Falls on the Orange River are examples. Another factor that contributes to the creation of rapids or falls is the incidence of rock strata that have proved resistant to the erosive effect of the rivers' flow. (Tropical rivers do not generally carry large quantities of stone or rock; instead, they have a tendency to carry loads of fine silt, produced by chemical weathering.)Although the Nile, the Zambezi, and the Niger rivers have large deltas (delta), their size does not compare with, for example, the enormous delta region of the Ganges and Brahmaputra rivers. In Africa the generally poor development of deltas is mainly because of the restricted extent of the coastal plain, together with the relatively narrow continental shelf, which provides neither sufficient room nor shallow enough water for the deposition of delta-forming material. The great speed with which most of the rivers flow into the sea is another factor inhibiting delta formation.The major drainage basins of Africa are those of the Nile, the Niger, the Congo, the Zambezi, and the Orange rivers and of Lake Chad.The Nile basin (Lower Egypt)There are two theories concerning the development of the Nile, which, it appears, originally consisted of two sections. The first theory is that the lower Nile had its source at about latitude 20° N, whence it flowed directly into the sea, while the upper Nile, issuing from Lake Victoria, flowed into an inland lake that covered the As-Sudd region in what is now The Sudan. The lake became filled with water, which then spilled over at its northern end and flowed into what is now the lower Nile. According to the second theory, the upper section originally flowed into a vast lake between Mount as Silsilah (near Luxor, Egypt) and what is now Aswān; this was tapped by the lower section of the Nile (Nile River) after the so-called Sebile erosion (which takes its name from the fact that the breakthrough by the lower Nile was identified at Sebile).The Nile, which is about 4,132 miles long, is the longest river in the world. From Lake Victoria it flows, as the Victoria Nile, into Lake Albert, from which it emerges as the Albert Nile. Farther north it is known as the Al-Jabal River. Thereafter, having received several tributaries, it becomes the White Nile, and finally the Nile, emptying at last into the Mediterranean Sea. Its major left-bank tributary is the Al-Ghazāl, and the largest right-bank tributaries are the Sobat, Blue Nile, and Atbara. Because of the numerous rapids and waterfalls, the Nile descends fairly rapidly from source to mouth, as do its major right-bank tributaries. This is especially true of the Blue Nile (Blue Nile River), which, after issuing from Lake Tana on the Ethiopian Plateau at a height of approximately 6,000 feet, flows for most of its length through a steep gorge. Swamps also interrupt the river's course. Of these, the largest is the As-Sudd, a vast area of floating swamp reeds, mostly papyrus.The river's regime is now controlled by a series of dams situated on the Nile itself or on one of its various tributaries; of these, the largest is the Aswan High Dam on the main Nile.The Niger basinThe Niger basin is the largest river basin of western Africa. The Niger River, which rises in the mountains of Guinea, enters the sea through its delta in southern Nigeria; it is about 2,600 miles in length. Rapids interrupt its course at several points, although some of these (such as below Bamako, Mali) have been submerged in waters impounded by dams.The Niger receives its largest tributary, the Benue (Benue River), which flows in from its left bank, in Nigeria. The valleys of both the Niger downstream from Taoussa and the Benue appear to be faulted troughs dating from the Early Cretaceous Period. Originally, the middle Niger was separate from the upper Niger, which flowed into an inland lake, the remnants of which now form the inland Niger delta. The middle Niger flowed southeastward to the sea; its valley eroded toward its headwaters, eventually tapping the inland lake and linking the middle with the upper Niger.The Congo basinWith a total area of about 1,335,000 square miles, the Congo basin consists of a vast shallow depression that rises by a series of giant steps to an almost circular rim of highlands through which the river has cut a narrow exit into the Atlantic Ocean. The present exit is geologically relatively recent, the previous exit being to the north of the present one.The Congo River is some 2,900 miles in length. Its many waterfalls and rapids cause its valley, like that of the Nile, to lose elevation quickly. The river's course is often constricted by gorges. The best-known are the Boyoma (Boyoma Falls) (Stanley) Falls at Kisangani, where the river swings through an arc to flow westward; in fact, the Boyoma Falls are no more than a series of unevenly spaced rapids at no great height, extending along a 60-mile stretch of the river. Downstream from Kisangani, the Congo is joined first by the Ubangi from the right and then by the Kasai—which rivals the Ubangi in the size of its drainage basin—from the left. Below its confluence with the Kasai, the main river cuts through the Cristal Mountains in a deep gorge, which at one point expands into Malebo (Stanley) Pool, a shallow lake measuring 22 miles in length and 14 miles in width. The Congo enters the sea through a swampy estuary that is about 6 miles wide at its mouth.The Zambezi basinThe Zambezi River is about 2,200 miles in length; it occupies a basin with an approximate area of 463,000 square miles. Originally, there were two rivers, corresponding to the upper and lower courses of the present river; the valley of the lower section eroded toward the headwaters until it captured the waters of the upper section. Although there are stretches of the river where the gradient is very gentle—a drop of only about three inches to the mile—the valley as a whole has a fairly steep gradient. There are numerous waterfalls, the most spectacular of which is the Victoria Falls. After these falls, the river winds through a number of deep gorges cut out of basalt and, after flowing through a broad valley, enters Kariba Gorge, which is more than 16 miles in length and is cut through paragneiss (a gneiss, or coarse-grained rock, in which bands rich in granular minerals alternate with bands containing schistose minerals, formed out of sedimentary rock). The Kafue and the Luangwa, the two main tributaries, which both flow through gorges, join the Zambezi on its left bank downstream from Kariba. At the mouth of the main river is a delta about 37 miles wide.The Orange basinThe Orange River is the longest in South Africa. Flowing across almost the entire width of the country, it makes its way from the highlands in the east through the Kalahari depression in the west to empty into the South Atlantic Ocean. Its major tributary, the Vaal River, is one of its northern headwaters; the two rivers together have a combined length of about 1,300 miles. Together with other major rivers on the continent, the Orange–Vaal river system shares the characteristic of flowing over steep gradients for numerous stretches of its course. The largest drop (about 400 feet) occurs at the Augrabies Falls.The Chad basinThe Chad basin constitutes the largest inland drainage area in Africa. Lake Chad (Chad, Lake), a large sheet of fresh water with a mean depth between 3.5 and 4 feet, lies at the centre of the basin but not in its lowest part. Lake Chad is fed by three major streams, the Komadugu Yobe, Logone, and Chari, but these are in danger of having their waters captured by the drainage systems of rivers that flow in opposite directions. Lake Chad itself, with an area of only some 5,000 square miles, was formerly much more extensive.For a detailed discussion of Lake Chad (Chad, Lake), the Congo River, the East African lakes, the Niger River, the Nile River, the Orange River, the Sénégal River, the Suez Canal, and the Zambezi River see individual articles.SoilsSoil typesIn general, soil types on the African continent may be divided into five or six broad categories. There are desert soils; chestnut-brown soils, which border the deserts; and chernozem-like soils (dark black soils rich in humus and carbonates), which are found immediately south of the chestnut soils from The Sudan westward to just beyond the Niger Bend (the bend in the middle course of the Niger River), and pockets of which are also found in East Africa, Zambia, Zimbabwe, and South Africa. In addition, there are black soils (often grouped with chernozems and found on the Accra Plains of Ghana); red tropical soils and laterites (leached red iron-bearing soils), which occur in the tropical wet-and-dry and equatorial climatic zones; and Mediterranean soils, found in the Atlas Mountains of North Africa and the Cape region of South Africa.The most important factors that affect soil formation are climate, parent material, relief, drainage, vegetation cover, and the passage of time. Where the land has been generally stable and fairly flat for prolonged periods, as in Africa, the climate becomes the major determinant of the soil groups. The different rocks are deeply weathered and are broken down into their common component elements to produce broadly similar soils under the same climatic conditions. Given sufficient time under a tropical climate, the differences in humus content of the great soil groups, which are introduced by vegetation types, are minimized. But within these groups there will naturally be differences in soil types as a function of local differences in physical factors.desert soilsThese soils are characterized by the general lack of organic content; by the types of rock reflected in them, the chemical weathering of which has been inhibited by the lack of water; and by the crusts or concretions of soluble salts on or just below their surface. While these crusts are in general thought to have been formed as a result of evaporation, it is nevertheless possible that they may have been formed under a wetter climate during the Pleistocene Epoch.Chestnut-brown soilsIn the semiarid areas bordering the desert, increased rainfall makes grass vegetation more plentiful, results in rocks becoming more weathered than in the desert, and produces better developed soils with a higher humus content. It is the humus content that, according to the amount present, gives the chestnut soils their characteristic light or dark brown colour. Chestnut soils also differ from desert soils because they receive enough water to wash out some of the salt accumulations either on the surface or immediately below it.Chernozem-like and black soilsAn unfailing characteristic of the chernozem is the presence of a subsurface zone of calcium carbonate, sometimes accompanied by calcium sulfate, which is left behind after all the soluble salts have been washed out. Grouped with them are the black soils, which should, perhaps, be differently classified, for their black colour is not necessarily due to high humus content but rather to the presence of certain minerals, as in the black soils of the Accra Plains, in Ghana.Red tropical soils and lateritesThe majority of tropical soils have shades of colour varying from yellow and brown to red. The reddish colour reflects the presence of iron oxides that form as a result of chemical weathering. At one time all tropical red earths or soils were indiscriminately referred to as laterites (laterite), but it is now clear that the term laterite should be confined to those tropical soils with large concentrations of iron and aluminum sesquioxides (insoluble compounds) that have formed a hard pan at or just below the surface. At the most advanced state of laterization, bauxite, from which aluminum is extracted, is formed. Most tropical soils are in varying stages of laterization, which is to say they are at various stages of accumulating insoluble compounds as the soluble elements are leached out. The compounds accumulate more readily in areas with a pronounced dry season and where the water table is not too far below the surface. If the top horizons (layers) of the soils should erode, the subsurface concentrations of sesquioxides are then exposed to the atmosphere, whereupon they crystallize irreversibly to form true laterite concretions.Mediterranean soilsMediterranean soils are generally deficient in humus, not so much because of sparse vegetation cover as because of the slowness of the chemical processes that convert the vegetable matter to humus. Low rainfall, occurring when temperatures are lowest, retards chemical weathering. The uneven surface relief of the regions where these soils occur also makes it difficult for mature soils to develop, since the land, except in the valley bottoms, is not sufficiently flat over wide enough areas to allow the soil-forming (parent) materials to remain in place and thus to be thoroughly weathered.Soil problemsSoil is the foundation of Africa's economic life, and as such its detailed study is most important. Failure to appreciate the physical and chemical properties of the soils has led to disastrous results for several projects for agricultural improvement.In studying the soils of Africa, it is essential not to lose sight of the importance of such social factors as the ability or inability of mostly uneducated farmers to judge the quality of the soil. Thus, schemes for transforming traditional systems of farming that are based on soil classification but that do not take into account local perception may have little chance of success.For desert soils to be productive they must be irrigated, as they are on the desert margins of North Africa; their excessive salinity or alkalinity must also be reduced. Compared to desert soils, the chestnut-brown soils are easier to work and are more productive under irrigation. Black soils tend to have a markedly crumbly structure and are sometimes difficult to plow. In the wet season, the black soils of the Accra Plains swell and become slippery, while in the dry season they shrink once more and crack to such an extent that they are said to plow themselves. Red tropical soils need careful handling. Despite their luxuriant vegetation cover, high temperatures coupled with humidity promote the rapid decay of organic matter and keep the humus content low. Erosion is a constant threat if the soils are exposed to the elements for any length of time; the soils remain cultivable only if the sesquioxides remain below the surface.In the Atlas and Cape regions, there is a clearer relationship between soil characteristics and parent material than in the humid tropical areas. Over expanses of limestone, for example, the soils contain large amounts of calcium compounds, some of which must be washed away or neutralized before the soils can become fully productive.ClimateFactors influencing the African climateA number of factors influence the climate of the African continent. First, most of the continent—which extends from latitude 35° S to about latitude 37° N—lies within the tropics. Second, the near bisection of the continent by the equator results in a largely symmetrical arrangement of climatic zones on either side. This symmetry is, however, imperfect because of a third factor—the great east–west extent of the continent north of the equator, in contrast to its narrow width to the south. In consequence, the influence of the sea extends farther inland in southern Africa. Moreover, a quasi-permanent subtropical high-pressure cell (the Saharan anticyclone) develops in the heart of northern Africa, while in southern Africa the belt of high pressure on land weakens during the time of high sun (the season when the Sun is overhead—in December and January in the south). A fourth factor consists of the cool ocean currents, which chill the winds that blow over them and thereby influence the climate of the neighbouring shores. Fifth, because of the extensive plateau surfaces of the continent and the absence of high and long mountain ranges comparable to, for example, the Andes in South America or the Himalayas in Asia, climatic zones in Africa tend to shade into one another, rather than to change abruptly from place to place. Finally, the high mountains have climatic zones of their own that vary with altitude.While these factors help to account for the broad climatic patterns of the African continent, there are, nevertheless, numerous local variations to be found from place to place within the same climatic zone. Urban areas, for example, have climates that often differ in many respects from those of the surrounding countryside. Typically experiencing higher average temperatures, urban areas also frequently have less wind and lower relative humidity; there is too little relevant data from Africa, however, to permit a detailed study of urban climates.The most important differentiating climatic element is rainfall; this, together with several other climatic elements, depends upon the characteristics of the dominating air mass. The air masses of relevance to the African climate may be broadly classified as maritime tropical, maritime equatorial, continental tropical, maritime polar, and continental polar. Of these, the least important are the continental polar air masses, which may occasionally bring intense cold to northern Egypt in December and January, and the maritime polar air masses, which are associated with rain-bearing depressions over the northern and southern extremities of the continent during the winter. With the exception of these, the continent is affected both by a continental tropical air mass to the north and by maritime tropical and maritime equatorial air masses to the south.These northern and southern air masses meet at the intertropical convergence zone (ITCZ). The hot, dry continental tropical air mass, which is present in the upper levels of the atmosphere, descends to the ground only at the convergence zone. Less hot than the continental tropical are the maritime tropical and maritime equatorial air masses, which originate from the Indian and South Atlantic oceans, respectively; they differ only in that the maritime equatorial air mass is unstable and brings rain, while the maritime tropical air mass, when fully developed, is stable and does not normally bring rain unless it is forced to rise by a high mountain.In July the ITCZ—following the sun—moves northward toward the area of low pressure over the Sahara; there, the maritime and continental tropical air masses converge, with the maritime air masses swinging inland from the sea. There is no rainfall on the northern side of the convergence zone, since the region is completely under the dry continental tropical air mass originating over the Sahara. At the ITCZ itself, however, precipitation is prolonged and intense as air converges between the maritime and continental air masses and is forced aloft. Immediately south of the convergence zone, rainfall is heavy because of the unstable nature of maritime tropical air over a heated land surface. South of the equator, at yet greater distance from the convergence zone, the maritime air masses are less heated, thick, and stable, and they bring hardly any rainfall, except over some of the East African highlands. Only the southern tip of South Africa receives rainfall at this time, from winter cyclones.During the period of low sun in the Northern Hemisphere (from December to January, when the sun has moved to its southern limit), the situation described above is reversed. The convergence zone moves southward, dipping into southern Africa. At this season the whole of northern Africa (except the Atlas Mountains) is under the dry continental tropical air mass, while southern Africa receives rainfall except in the Cape region and on the southwest coast, where the maritime air mass remains stable offshore over the cool Benguela Current.Climatic regionsWhen considered in detail, the movement of air masses and their effects provide the basis for a division of the continent into eight climatic regions. These are the hot desert, semiarid, tropical wet-and-dry, equatorial (tropical wet), Mediterranean, humid subtropical marine, warm temperate upland, and mountain regions.The hot desert region consists of the Sahara and Kalahari deserts, which are always under the influence of dry continental tropical air masses, and the northern Kenya–Somali desert, the aridity of which is principally caused by the stable nature of the maritime air masses that pass over it throughout the year. The stability of these maritime air masses is induced by their passing over the cool body of water offshore. In addition to aridity, the desert climate is characterized by high mean monthly temperatures; the diurnal (daily) temperature range is, however, greater than the annual range of the mean monthly temperature.Semiarid climatic regions fringe the desert areas and include the greater part of the land south of the Zambezi River. They differ from true desert regions in being just within reach of the ITCZ in the course of its seasonal movement and therefore receiving more rainfall. Temperatures are about the same as those in the desert regions.The tropical wet-and-dry region is often called the savanna climatic region; this implies, incorrectly, that all areas with savanna vegetation have this type of climate. This region covers a little less than half of the total surface area of the continent, extending toward the equator from the semiarid areas. The great distinguishing feature of this climatic region is the seasonal character of its rainfall. During the period of high sun the maritime air masses produce up to six months of rainfall—the length of the rainy season depending on nearness to the equator. The rest of the year is dry. In a few places—for example, on the coast of Mauritania and Senegal—there is also a little rainfall in the period of low sun. As in the desert and semiarid climatic zones, mean monthly temperatures show less variation than daily temperatures. In western Africa the period of low sun corresponds to the harmattan season. The harmattan is a warm, dry northeasterly or easterly wind that blows out of the southern Sahara and is frequently laden with large quantities of sand and dust.Regions with the equatorial, or tropical wet, type of climate, or variants thereof, are the wettest in Africa. There are two peak periods of rainfall corresponding to the double passage of the ITCZ. Because areas with an equatorial climate are constantly covered by warm maritime air masses, variations in their monthly and daily temperatures are less pronounced than in the tropical wet-and-dry regions.Marked variations in the rhythm of equatorial climate sometimes occur; for example, the rainfall may be monsoonal and the second rainy season may be all but nonexistent. But the most notable anomaly can be observed on the West African coast from around Cape Three Points, Ghana, eastward to Benin, where, although the bimodal rainfall regime prevails, the total annual precipitation is less than 40 inches (1,000 millimetres). Among the many explanations that have been suggested are that the presence of a cold body of water offshore chills the lower layers of the maritime air mass and makes it stable; that the body of cold air that forms offshore diverts the incoming airstreams to the west and east of the anomalously dry area; that there is a strong tendency for the winds to blow parallel to the shore during the rainy seasons; that the absence of highlands deprives the region of orographic (mountain) rainfall; that fluctuations in the offshore, moisture-bearing winds occur during the rainy season and reduce rainfall; and that local meteorological peculiarities of thunderstorms contribute to the reduction in rainfall.In the northern and southern extremities of the continent there is a dry summer subtropical, or Mediterranean, type of climate. Rain falls only in winter (December–January in North Africa, June–July in southern Africa), although in some localities it may fall in autumn (September in North Africa, April in southern Africa). Mean monthly temperatures are lower than in tropical climates, dropping to about 50° F (10° C) in winter, while summer (June–July in North Africa, and December–January in southern Africa) temperatures may sometimes exceed those of tropical climates. Clear blue skies are characteristic.The humid subtropical marine climate is restricted to the southeast coast of Africa. This region is characterized by rainfall throughout the year, but it is heaviest in summer. In South Africa, south of KwaZulu-Natal, the winter rainfall is more pronounced, and the temperatures are a little lower than in the north. Thus, at Port Elizabeth there are six months when temperatures are below 62° F (17° C), while at Durban mean monthly temperatures do not fall below 64° F (18° C).The warm temperate upland climatic region is found on the Highveld of southern Africa. Its rainfall regime is similar to that of the tropical wet-and-dry climate, but temperatures are greatly modified by the altitude; frost, for example, occasionally occurs in Lesotho. Toward the coast the climate shows maritime characteristics, and there is a tendency toward winter rainfall.The mountain climatic region includes the high mountain areas of Ethiopia and the lake region of East Africa. In some respects the climate is similar to the warm, temperate upland climate, except that temperatures are even lower and snow occurs on the tops of the highest peaks, such as Kilimanjaro. The rainfall regime is similar to that of the adjacent lowland areas.Kwamina Busumafi DicksonPlant lifeAfrican vegetation develops in direct response to the interacting effects of rainfall, temperature, topography, and type of soil; it is further modified by the incidence of fire, human agriculture, and grazing and browsing by livestock. Of the total land area of the continent, forests cover about one-fifth; woodlands, bushlands, grasslands, and thickets about two-fifths; and deserts and their extended margins the remaining two-fifths.Ecological relationshipsUntil about two million years ago Africa's vegetation had always been controlled by the interactions of climate; geology, soil, and groundwater conditions (edaphic factors); and the activities of animals (biological factors). The addition of humans to the latter group, however, has increasingly rendered unreal the concept of a fully developed “natural” vegetation—i.e., one approximating the ideal of a vegetational climax. Nevertheless, in broad terms, climate remains the dominant control over vegetation. Zonal belts of precipitation, reflecting latitude and contrasting exposure to the Atlantic and Indian oceans and their currents, give some reality to related belts of vegetation. Early attempts at mapping and classifying Africa's vegetation stressed this relationship: sometimes the names of plant zones were derived directly from climates. In this discussion the idea of zones is retained only in a broad descriptive sense.As more has become known of the many thousands of African plant species and their complex ecology, naming, classification, and mapping have also become more particular, stressing what was actually present rather than postulating about climatic potential. In addition, over time more floral regions of varying shape and size have been recognized. Many schemes have arisen successively, all of which have had to take views on two important aspects: the general scale of treatment to be adopted, and the degree to which human modification is to be comprehended or discounted.Once, as with the scientific treatment of African soils, a much greater uniformity was attributed to the vegetation than would have been generally acceptable in the same period for treatments of the lands of western Europe or the United States. Quite the opposite assumption is now frequently advanced. An intimate mosaic of many species—in complex associations and related to localized soils, slopes, and drainage—has been detailed in many studies of the African tropics. In a few square miles there may be a visible succession from swamp with papyrus, through swampy grassland and broad-leaved woodland and grass to a patch of forest on richer hillside soil, and finally to succulents on a nearly naked rock summit.The span of human occupation in Africa is believed to exceed that of any other continent. All the resultant activities have tended, on balance, to reduce tree cover and increase grassland; but there has been considerable dispute among scholars concerning the natural versus human-caused development of most African grasslands at the regional level. Correspondingly, classifications have differed greatly in their principles for naming, grouping, and describing formations: some have chosen terms such as forest, woodland, thornbush, thicket, and shrub for much of the same broad tracts that others have grouped as wooded savanna, savanna, and steppe. This is best seen in the nomenclature adopted by two of the most comprehensive and authoritative maps of Africa's vegetation that have been published: R.W.J. Keay's annotated Vegetation Map of Africa South of the Tropic of Cancer (1959) and its more widely based successor, The Vegetation Map of Africa (1983), compiled by Frank White. In the Keay map the terms “savanna” and “steppe” were adopted as precise definitions of formations, based on the herb layer and the coverage of woody vegetation; the White map, however, discarded these two categories as specific classifications. Yet any rapid demise of savanna in its popular and more general sense (i.e., as dry tropical grassland or mixed woods and grassland) is doubtful.The vegetational map of Africa and general vegetation groupings used in this article mainly follow the White map and its extensive annotations, although some 100 specific types of vegetation identified on the source map have been compressed into 14 broader classifications.Vegetational zonesLowland rain forestAfrican lowland rain forests occur along the Guinea Coast of West Africa and in the Congo basin. The full development of this tropical formation requires continuously warm conditions and an annual rainfall exceeding 50 to 60 inches (1,270 to 1,520 millimetres) distributed fairly evenly over the year. The vertical limit is about 3,500 to 4,000 feet. This multistoried, highly diverse, extensive, and potentially self-perpetuating assemblage has been described by some as the source of virtually all tropical floristic diversity. No other part of the world sustains a greater biomass (total weight of organic matter in a given surface area) than lowland tropical rain forests. Even though the speciation (proliferation of distinct types of plant) within the African rain forests is notably poorer than that of its counterparts in Southeast Asia and the Amazon basin of South America, these forests sustain a huge multiplicity of life forms, occupying different strata (generalized levels of plant height) and niches (separate, small-scale habitats). Characteristically, tropical rain forest is composed of a ground story, from 6 to 10 feet tall, of shrubs, ferns, and mosses; a middle story of trees and palms 20 to 60 feet in height; and a dominant top canopy consisting of trees up to 150 feet high with straight unbranched trunks, buttressed roots, and spreading crowns of perennial leafage. The large branches of these crowns provide niches for epiphytes, including orchids, ferns, and mosses. Lianas tie trees to one another, parasitic species cling to trunks and branches, and strangler figs (Ficus pretoriae) put down aerial taproots. Nevertheless, these are not “impenetrable” jungles. It has been suggested that some early European travelers and pioneer botanists may have exaggerated the difficulties of human penetration because they journeyed along atypical waterways and along tracks where disturbance of the original vegetation had thickened the regenerating ground layer. In true rain forests, grasses are adventitious (occurring in consequence of fortuitous intrusions). Elephant grass (Pennisetum purpureum) can grow abundantly in areas where the vegetation has been disturbed, providing good fodder for grazing animals when young but quickly becoming rank, coarse, and a refuge for insects. Cogon grass (Imperata cylindrica) is a troublesome grass on depleted and fire-seared ground.Eastern African forest and bushLowland forests and evergreen bushland form a long belt of land some 125 miles broad along the Indian Ocean. From various causes—notably the monsoonal climate, freely draining soils, and long historical impact of humans—these forests are much more limited in their structure (physical form), speciation, and robustness. On more favoured terrain—such as estuarine fringes, the seaward flanks of the islands of Zanzibar and Pemba, and hill masses athwart the rain-bearing southeast monsoon—forest and a close broad-leaved woodland are still dominant. Where land is in a rain shadow, in areas of unfavourable geology (e.g., raised coral reefs), and near cities and small ports, thorny bush, succulent shrubs, and scrawny grassland prevail. Nevertheless, the region now sustains a number of economically important domesticated trees—both indigenous and exotic—such as the coconut palm, cashew, mango, and (especially on Zanzibar and Pemba) clove.mangrove swampMangroves include a variety of species of broad-leaved, shrubby trees (10–40 feet high) that fringe muddy creeks and tidal estuaries. They require warm, saline water—hence their distribution along tropical coastlines. Often they form nearly impenetrable stands, for which the easiest access is by sea. The trunks and roots are termite-resistant, and they have long been favoured as a building material and for making charcoal.Broad-leaved woodland and grasslandThis classification constitutes one of the most extensive composite categories now recognized and includes much of the land formerly labeled as savanna. Two broad bands extend across the continent, one from about 7° to 12° N latitude and the other from about 8° to 22° S latitude. Structure and floristic composition vary greatly with the increase of latitude, both in the north and the south. Annual rainfall averages 35 to 45 inches, with marked seasonality of occurrence and considerable fluctuations from year to year, both in total rainfall and in the onset of rainy periods. The woodlands of western Africa strikingly resemble those south of the equator. In both areas, undulating wooded interfluves on light soils successively alternate with swampy, clay-based valley grasslands (called fadamas in Nigeria and dambos in Zambia and Malaŵi) in a topographically linked sequence of soils called a catena.Trees, 30 to 50 feet high, are typically deciduous and often fire-resistant, since much of this land is burned annually. Common West African species include types of Isoberlinia (a spreading leguminous tree of the pea family), Daniellia (a leguminous tree with white bark), and Lophira (a tree with strap-shaped leaves that is said to yield the most durable timber in the region). Other hardwoods, forming distinct communities, are Combretum and Terminalia, which are better suited to the drier areas. Prevalent southern equivalents include Brachystegia (a leguminous hardwood, the bark of which formerly was used to make cloth) and Julbernardia (another plant of the pea family resembling Isoberlinia). Over much of the interior of Tanzania, in areas of reduced rainfall and poorer soils, a light-canopied, sustained woodland called Miombo forest rises above a rather scrawny ground layer. This is an excellent habitat for bees, and honey has long been gathered there.Because of periodic burning, tall grasses have become dominant over large expanses of plateau land, which sometimes contains few, if any, of its original trees. The tall, coarse red grass Hyparrhenia can form prominent stands, but it makes poor grazing land and often harbours insects that spread disease. Much better for the pastoralists are induced swards of Themeda.For centuries humans have selectively retained certain economically important tree species in areas cleared for farming; the effect has been to create what is called “farmed parkland,” in which a few favoured trees rise above the fields. Examples include the shea butter nut tree (Butyrospermum), common in Ghana and Côte d'Ivoire; Acacia albida, found in Senegal and Zambia; and the truly domesticated baobab (Adansonia digitata), which is perhaps the most widely distributed.Thorn woodland, grassland, and semidesert vegetationToward the margins of the tropics the vegetation cover becomes lower and thinner as the fluctuating transition to desert vegetation ensues. In the same progression the concept of an annual rainfall (nominally 5 to 20 inches) yields to the reality of extreme unreliability in both incidence and expectation. Under such restraints a definitive “boundary” with the desert becomes meaningless. Moreover, there appears to have been a trend toward declining precipitation in the last half of the 20th century, and human impact certainly has enhanced the natural deprivation of plant life in the marginal regions. The southern margin of the Sahara—roughly between the latitudes of 15° and 20°—is called the Sahel (Arabic: Sāḥil; “shore,” or “edge”), the word being extended by implication to comprehend the fluctuating margins of the great sand seas of the Sahara to the north. The southern equivalent covers much of the Kalahari, which is often called a desert but is more properly a thirstland.Thorn woodland displays a predominance of xerophytic, sometimes succulent or semisucculent trees, such as acacia, Commiphora (the myrrh tree), or Boscia (an evergreen hard-leaved tree). The occurrence of the bunched and thorny desert date (Balanites) seems to accompany land impoverishment. A relatively luxuriant shrub layer, often forming dense thickets, is found in conjunction with succulents, such as aloes, Sansevieria (a fibrous species), and Adenium, or desert rose (a succulent shrub with smooth grey bark, a huge water-storing base, and beautiful red or pink flowers), and smaller euphorbias.Farther toward the desert, tree growth and perennial grass—surviving in narrow strips along watercourses—separate much larger areas of sparse annual grasses (Cenchrus in western Africa, Eragrostis south of the equator, and Chrysopogon on the margins) and scattered low shrubs, often mainly acacias. Shrubs may often be salt-tolerant. While shrubs may die from inadequate moisture, they are little affected by the rare fires that occur.Afromontane vegetationAll high mountains (mountain ecosystem) exhibit azonality; i.e., their vegetation differs from that found in the climatic zones from which they rise. The differences manifest themselves as progressive modifications, which are usually well stratified and reflect altitude-dependent climatic changes. Generally, as elevation increases temperature decreases (to the point where frost and even glaciation can occur) and precipitation increases (although above a certain level precipitation decreases markedly). Mountainous terrain can retain ancient climatic conditions—making possible, for example, the survival of relict species—and the relative inaccessibility of the higher elevations to humans has helped preserve more of the vegetal patterns of the past.Vegetation strata typically are skewed with regard to slope orientation (aspect). This is mainly due to a contrast between exposure to rain-bearing winds and shadowing from them but may also reflect long-term history. If lower slopes rise abruptly from the base (as they often do in Africa), then a distinct boundary between vegetation formations may be clearly distinguished; if the rise is gentle, vegetations merge (as in the western Kenyan highlands). (All the circumstances mentioned above are represented in the African mountain systems, but for purposes of illustration the vegetational map identifies only areas of altitudinal modification. Thus, some areas that are included are not tropical, such as parts of the Red Sea Hills and the mountains of South Africa and Lesotho.)Altitudinal modifications of vegetation are clearly discernible on the high East African peaks near the equator (e.g., Kilimanjaro and Mounts Kenya and Elgon), and a rich forest belt—much reduced upslope by human activities, except where the land has been reserved—clothes the zone that receives the maximum rainfall and is free of frosts (up to about 5,000 to 6,000 feet). Such mountains have great human importance as watersheds and as repositories of native plants.desert vegetationThe Sahara has one of the lowest species densities in the world, and a sustained vegetation cover (which can include trees and bushes) occurs only in the massifs and oases. Elsewhere, the vegetation is discontinuous and consists of two main types: perennials with huge root systems and sparse aerial parts, often protected by waxy cuticles, thorns, and hairs; and ephemerals (ephemeral) with slight root systems and little foliage but with the ability to flower profusely immediately after occasional storms and then to seed quickly and abundantly. The stony and rocky expanses give more hold for plants than do the vast areas of shifting sands. In some areas with slightly more rainfall, grass tufts may grow 50 yards apart. Aristida is the dominant grass, and for brief periods it can yield a nutritious forage called ashab.The Namib is one of the world's driest deserts. The area along the coast, however, is almost always foggy, and succulent shrubs (such as aloes) manage to survive on this moisture. The Namib also contains the strange tumboa, or welwitschia (Welwitschia mirabilis), which may live 100 years or more.Karoo-Namib shrubland (shrub)In this drought-prone land, soils are often shallow, even saline. The low shrubs that grow there can be divided into two groups: woody plants, such as species of Acacia and Pentzia and the saltbush (Atriplex); and succulents, including aloes, euphorbias, and Mesembryantheum. Aristida and Themeda are characteristic grasses. Every year the blossoms of bulbous plants lay short-lived carpets of colour. Being both drought-resistant and high in minerals, many of the shrubs can provide useful grazing for goats and sheep.Highveld grasslandThe grassland classification is restricted to regions with 10 percent or less woody plant cover. The Highveld meets this definition and probably owes much to unaided nature for its creation and perpetuation, since fires caused by lightning strikes are relatively frequent. Its extent has always been fairly precisely defined: areas with more than 15 inches of rainfall during the summer. Highveld vegetation, though modified considerably by human activity, traditionally has been differentiated into sweet veld (dominated by Themeda) or sour veld (Andropogon and Eragrostis), the latter making poorer pasturage.This zone is determined chiefly by its climate, which is characterized by very dry summers and mild, rainy winters, but it has long been much differentiated by its inhabitants; large tracts have been degraded into maquis (macchie), garigue, or dry semidesert (steppe) vegetation. Maquis consists of dense scrub growths of xerophytic (drought-resistant) and sclerophyllous (leathery) shrubs and small trees, which are often fire-resistant. Garigue characteristically is found on limestone soils and has more woody growth, including evergreen and cork oaks (Quercus suber). The higher slopes of the Atlas Mountains once carried large stands of pine and cedar, but they have been much depleted. Typical grasses, progressing from the coast to the desert, are Ampelodesmos, Phalaris, and Stipa.This region constitutes the southern counterpart of the Mediterranean zone, although (with the exception of the Atlas Mountains) it is richer in its vegetation potential. There were once considerable enclaves of true evergreen bushland, which have reverted to shrubland (fynbos). Sclerophyllous foliage and proteas abound. Although grassy tracts occur on the mountains, they are characteristically unusual lower down. Beyond the Cape Ranges, fynbos grades into karoo.Physically and biologically, Madagascar has long formed a separate entity. White has identified eastern and western regions of endemic (unique) vegetation. In the eastern centre, about one-sixth of the plant genera and more than three-fourths of the thousands of species are regarded as endemic. The Madagascar rain forest has shorter trees and a somewhat drier climate than its equatorial counterpart and contains its own dwarf palms (Dypsis) and bamboos (Ochlandra). The western deciduous forest stands in the rain shadow; some of its trees resemble Mediterranean oaks. The southern thickets have prominent euphorbias and species of the Didiereaceae family. The island has much degraded secondary forest (locally called savoka) along the eastern and northern coasts.In addition to the major types of vegetation described above, a special vegetation called sudd (literally meaning “barrier”) occurs in the great Nile, Niger, and Zambezi drainage systems of the African interior plateau. Characteristic is the sudd along the White Nile River in The Sudan and Uganda. Sedges (especially papyrus), reeds, and other water plants—including the floating Nile cabbage (Pistia stratiotes)—form masses of waterlogged plant material that are largely unproductive and are a nuisance to fishing and navigation. Pistia has become an unwelcome invader of Lake Kariba, the body of water formed by the impounding (1959) of the Zambezi River in the Kariba Gorge.Long-term changes in vegetationAfrica's basic vegetational zones are believed to have existed in approximately the same climatically controlled series and with the same characteristically developed species for a long period of time; and, indeed, some ancient African plant families—such as the cycads, which evolved some 200 million years ago—still have living representatives. Nonetheless, the continent's vegetation has been altered continuously by geologic and climatic changes and by the movement of the caloric (heat) equator. The past million years have been a time of unusually rapid changes, with major consequences for Africa's vegetation.The vegetational history of Africa is of great scientific relevance. Studying the lichens growing in the high East African mountains, for example, may yield a better understanding of the continent's climatic trends, and a knowledge of past conditions in the Sahel might help explain what influence natural phenomena have had on the disastrous droughts of the region since the late 1960s.Geologic influencesThe two most important geologic modifications of vegetation have been the very ancient separation of Madagascar from the mainland, which gave rise to the distinct speciation of the island's flora, and the long-continuing faulting and vulcanism along East Africa's huge rift system that has thrown up high ranges (e.g., the Ruwenzori between Uganda and Congo [Kinshasa]) and great volcanoes (Kilimanjaro) and has thus created and reshaped Afromontane flora.Climatic influencesThe repercussions of the great Pleistocene Ice Ages of Europe have constituted the most notable climatic influence on African flora in relatively recent geologic history. These consisted of a succession of colder periods marked by glacial advances, interrupted by warmer, drier interglacials; the last series of these ended between about 5,000 and 10,000 years ago. Tropical Africa experienced contemporaneous fluctuations in its climate, although it is misleading to infer any simple equivalences between these fluctuations and the European periods of glacial advances and retreats.During the wetter times (pluvials) in Africa, equatorial forests spread, separating northern woodlands from their southern counterparts (with consequent species differentiation); mountain vegetation descended onto the plateaus; and there is evidence that the Saharan climate was greatly ameliorated, much to the advantage of humans. During the warmer, drier interpluvials the existing vegetation was degraded in many zones. Dunes spread from the Sahara and over the Kalahari, for example, and their fossilized alignments—now vegetated—can be traced across the thorny woodlands and grasslands of Niger, Nigeria, Namibia, and Botswana.Human influencesThe greater part of the reduction of Africa's natural vegetation has happened in the last 2,000 years—probably since the late 19th century for the tropical portions—the time during which humans have been most numerous and active. Pastoralism, agriculture, the rapid growth of human and livestock populations, the expansion of cities and towns, and the external demands for primary resources have made ever-greater demands upon the land for sustenance and perceived economic betterment. Much is known of the detailed processes of vegetation modification along the Mediterranean, since they have been observed and studied since classical times, and a good deal is also known from the more than three centuries of study of the Cape area of South Africa; but until the late 19th century very little was understood about these processes in tropical Africa. Indeed, the time scale of actual human impact on African vegetation may be causally linked to the awareness of it by Europeans.Within the tropical forests (forest) and woodlands, fire undoubtedly has been the great human agent of clearance and degradation, of far greater efficacy than felling, bark-ringing, or uprooting—at least until the introduction of modern plantation agriculture and logging. Hunters, pastoralists, and cultivators have all fired the land for centuries and have gathered wild foodstuffs, thatch timber for construction, and fuelwood from the volunteer (i.e., uncultivated or self-generating) vegetation. The long-term effects of such activity bear directly upon the debated question of the origin of the savannas.In earlier times, African cultivators found the fabric of the tropical rain forest comparatively difficult to modify substantially. In the 20th century, however, it has been greatly reduced in extent (such as in Sierra Leone), patched and frayed (Nigeria), and exploited for timber exports (Gabon). Moreover, many of tropical Africa's largest cities and busy seaports are in this zone. The most diverse and seemingly inexhaustible floral realm in Africa has therefore become a cause for widespread concern.Conserving the vegetationPerceptions of the need for environmental conservation in Africa held by those outside the continent are sometimes expressed in terms that seem opposed to the legitimate priorities and aspirations of African peoples (in meeting which agriculture and livestock management must remain crucial). It is not surprising that projections based upon the assumptions from these external sources frequently end in pessimism. A more constructive approach is to identify ways in which to more fully integrate wild plant life, crops, and animals, which can be expressed in the concept of productive countryside. The capacity and precision of resource surveys have been greatly enhanced by remote sensing, and this has been coupled with the worldwide transmissibility of information. Research and interest in agroforestry have expanded and become institutionalized. Above all, however, confidence must be put in the capacities of many millions of African farmers to expand agriculture while working toward reintegration with wild plant life.Animal lifeAfrica includes two regions of the zoographic area known as the Paleotropical realm: the Afrotropical region, which comprises the continent south of the Sahara and the southwestern part of Arabia, and the Madagascan region. The continent also includes a southern part of the Palaearctic (Old World) region of the Holarctic realm (i.e., the lands of the Northern Hemisphere), consisting of North and northwestern Africa south to roughly the tropic of Cancer.Genera and distributionAfrica is best known for the enormous diversity and richness of its wildlife. It has a greater variety of large ungulates (ungulate), or hoofed mammals (mammal) (some 90 species), and freshwater fish (2,000 species) than any other continent.MammalsThe main group of herbivores (herbivore) are the African antelope, which belong to four subfamilies of the ox family (Bovidae). The first subfamily is the oxlike Bovinae, which is further subdivided into the African buffalo (see photograph—>) and the twist-horned antelope, including the eland (the largest of all antelope), kudu, nyala, and bushbuck. The second subfamily is the duiker, a small, primitive bovid that lives in the thickets, bush, and forests. Third is the “horse antelope,” further divided into sabre-horned sable, roan, and oryx antelope; the “deer antelope,” kongonis, hartebeest, topi, gnu (wildebeest), and blesbok, all mostly inhabitants of the open plains; and the “marsh antelope,” waterbuck, lechwe, kob, puku, and reedbuck. The fourth subfamily is the antelope proper, divided into two distinct tribes, the first of which includes royal, dik-dik, klipspringer, oribi, steenbok, and grysbok and the second, gazelle, impala, springbok, and gerenuk. Other well-known large African herbivores include the zebra, giraffe, hippopotamus, rhinoceros, and African elephant.Probably no group of animals is more identified with Africa than its Carnivora (carnivore) (the order of flesh-eating mammals), of which there are more than 60 species. In addition to the better-known big (or roaring) cats—the lion, leopard, and cheetah—are the wild dog, hyena, serval (a long-limbed cat), wildcat, jackal, fox, weasel, civet, and mongoose. These predators and scavengers are vital in maintaining the ecological equilibrium of the areas that they inhabit.The primates (primate) include some 45 species of Old World monkeys, as well as two of the world's great apes: the chimpanzee and the world's largest ape, the gorilla. Presimian primates—such as pottos (African lemurs) and galagos (bush babies, or small arboreal lemurs), as well as Lorisidae (a family of arboreal lemurs, moving with a slow, delicate crawl)—are mainly small and nocturnal, but in Madagascar, where there are no true monkeys, the world's most diverse assemblage of large and small diurnal and nocturnal presimian lemurs survives.Marine mammals include one Mediterranean and one South African seal (the Cape fur seal) and two Sirenia (an order of aquatic herbivores)—the dugong and the manatee. In addition, whales, porpoises, and dolphins frequent Africa's coastal waters.Africa's large number of endemic mammal species is second only to that of South America. These include several families of the ungulate order Artiodactyla (composed of mammals with an even number of toes), such as giraffes and hippopotamuses. Some families of Carnivora—such as civets (of the Viverridae family), their smaller relations the genets, and hyenas—are chiefly African. The rodent family of jumping hares (spring hare) (Pedetidae) is endemic, and one order, the aardvark (Tubulidentata)—a large nocturnal burrowing mammal, with one species—is exclusively African. Madagascar also has a remarkable insect-eating family, the tenrecs (animals with long pointed snouts, some of which are spiny and tailless).Birds (bird)South of the Sahara the birdlife includes nearly 1,500 resident species, to which must be added another 275 species that are either resident in northwestern Africa or else are Palaearctic winter migrants; the migrants once totaled perhaps two billion individuals, but their numbers have been reduced considerably by severe droughts and by human land use and predation. Birds are mainly of Old World families, but of those that are endemic the most noteworthy are perhaps the ostrich (see photograph—>), shoebill, hammerkop (a brown heronlike bird), and secretary bird (a large long-legged predatory bird) and the touracos (brightly coloured birds, some with helmetlike crests). Other families, such as bustards, sand grouse, honey guides (small dull-coloured birds, several species of which are noted for leading people to the nests of honeybees, in order to feed on them after the nests have been broken), and larks are predominantly African. There are many avian predators of land mammals, including eagles, hawks, and owls; more of fish, such as storks, waders, and a few species of kingfishers; and even more of insects, this latter group usually being of benefit to humans. Scavengers include vultures and the large marabou stork.Reptiles (reptile) and amphibiansReptiles, of which there are few endemic families, have mainly Old World affinities. Those most likely to be seen include lizards of the agamid family, skinks (a family of lizards characterized by smooth overlapping scales), crocodiles, and tortoises. Endemic reptiles include girdle-tailed and plated lizards. Within the African realm lizards of the iguana family and boa constrictors occur only in Madagascar. Large vipers are abundant and varied; certain species have extremely toxic venom, but they are seldom encountered. A wealth of both colubrine snakes (with fangs at the posterior end of the upper jaw) and elapine snakes (with fixed poison fangs at the front of the upper jaw) include such highly venomous elapine species as mambas.Amphibians (amphibian) also belong mainly to Old World groups. Salamanders and hylid tree frogs (having teeth in the upper jaw) are confined to the Palaearctic northwest. Abundant commoner frogs and toads include such oddities as the so-called hairy frog of Cameroon, whose hairs are auxiliary respiratory organs. The frog subfamily Phrynomerinae is exclusively African.Arthropods (arthropod)Africa possesses an abundant and varied population of arthropods (which include insects and other segmented invertebrates). Among them are found large butterflies of the Charaxes (brush-footed) and Papilio (swallow-tailed) genera, stick insects, and mantises, grasshoppers, driver, or safari, ants (tropical ants that travel in vast, serried ranks), termites, and dung beetles. Spiders abound throughout the continent, and scorpions and locusts can also be plentiful locally. Periodically huge swarms of locusts spread over wide areas, causing enormous destruction to vegetation. Other serious pests are mosquitoes, which act as vectors in the spread of such human diseases as malaria, and tsetse flies, which transmit the parasite that causes African trypanosomiasis (sleeping sickness) in humans and nagana in livestock.Aquatic lifeFreshwater fish include both remarkable archaic forms and examples of rapid recent evolution. Among the ancient forms are lungfish (Protopterus), bichirs, or lobefins (Polypterus), and reedfish (Calamoichthys), all of which can breathe air—a property also possessed by certain catfish (Clariidae), which are able to travel overland for some distance in wet weather. Characteristic of more recent evolutionary trends are the approximately 200 species of fish found in Lake Nyasa, four-fifths of which occur only there.The coelacanth, an archaic marine form believed extinct for more than 60 million years, was discovered to be alive off the east coast of South Africa in 1938, and since then many others have been found. A rich and varied invertebrate animal life on the east and west coasts includes marine organisms typical of the Indo-Pacific and Atlantic oceans. Coral reefs and associated organisms are mainly found in the warm waters of Africa's east coast, while the southwest and west coasts—washed, respectively, by the cold Benguela and Canary currents—abound in fish.Origin and adaption of African faunaAt one time most African fauna (faunal region) was thought to derive from elsewhere. There is no doubt, however, that as little as 15,000 years ago an amelioration of the present Saharan climate enabled such typical Ethiopian forms as clariid catfish to reach the river systems of North Africa. Likewise, Palaearctic animal life and vegetation appear to have extended far south into the Sahara, and the white rhinoceros apparently lived beside elklike, typically Palaearctic deer.Within the Ethiopian region, repeated climatically controlled expansion and contraction of vegetational zones resulted first in organisms establishing themselves in numerous specialized ecological communities (niches) of plants and animals and second in the proliferation of those species that successfully adapted themselves to the prevailing conditions. The spread of forests during the pluvials, separating northern and southern wooded grasslands, led to the evolution of such closely related northern and southern species of antelope as the kob and puku, the Nile and common lechwe, and the northern and southern forms of white rhinoceros.Some subfamilies of Bovidae, like the spiral-horned antelope (Tragelaphinae), have adapted to almost every ecological environment—forest, woodland, grassland, Afro-Alpine zones, and even to sudd vegetation. Others, like the hartebeests (Alcelaphinae), which inhabit savannas and grasslands, are less adaptable.Freshwater fishes demonstrate the existence of the relation to one another of former river systems and lakes. Large rivers containing Ethiopian fish evidently existed quite recently in the northern Sahara. The fish life of the now-isolated Lake Rudolf (Lake Turkana), in East Africa, demonstrates that the lake was once connected to the Nile, though Lake Victoria, the present source of the White Nile, was not. Lake Kivu, too, was formerly connected with the Nile, but as a result of volcanic activity it is now part of the Congo drainage system.In earlier periods the animal life was even more remarkable than today. Fossil deposits have revealed sheep as big as present-day buffalo, huge hippopotamuses, giant baboons, and other types similar to existing species. These huge types probably lived in pluvial periods, dying out as aridity increased. Smaller types survived.The effects of humansUntil they acquired firearms, humans made relatively little impact on animal numbers or—with some exceptions—their range. From the last half of the 19th century, however, and particularly since 1940, direct or indirect human wastage of Africa's animal life (endangered species) has been intense and has reduced stocks considerably. The antelope known as the Zambian black lechwe, for example, believed to have numbered 1,000,000 in 1900, had been reduced to less than 8,000 by the late 20th century, and the population of African elephants declined from 2,000,000 in the early 1970s to some 600,000 by 1990, largely because of poaching for the ivory trade. The African white rhinoceros reached the verge of extinction in 1980.Though European hunters and colonists were rightly blamed for much of the decline at its onset, hunting and destruction and the disturbance of habitats by Africans have become more important. rinderpest, an acute, and usually fatal, infectious disease of livestock, entered Africa with domestic stock in the 1890s and ravaged herds of indigenous ungulates. The accelerated spread of agriculture and stock raising involving the destruction of forests, as well as heavy grazing and burning of vegetation, eliminated large animals from wide tracts. In the southern Sudan, for example, political strife and warfare in the 1960s entirely eliminated wildlife from some areas. The demand for fancy leather and fur has also endangered the Nile crocodile and the leopard.Humans, however, have been of benefit to many smaller species. Dams and irrigation schemes, for example, have provided habitats for waterfowl, frogs, and fish, and the spread of grain crops has encouraged certain pests. Even the patchy cultivation of forests has resulted in the development of a mosaic of habitats that can provide new, if small, niches for some species.There are still sufficiently large tracts of relatively unspoiled country in which animal life may be studied in its environment. The complementary roles of wild ungulates, for example, show that in any area inhabited by a wide variety of species, the grass is grazed in regular succession and at different stages of growth—for example, by zebra, gnu, hartebeest, and gazelle—while specific adaptations enable a still greater variety to survive. A much smaller variety of domestic stock cannot duplicate such effects. Overpopulation by domestic or wild species may upset the delicate natural balance, as may be seen by the example of elephant overpopulation in Murchison Falls (Kabalega) National Park (Murchison Falls National Park), Uganda, and in Tsavo National Park, Kenya; whether the elephants survive or not, they have ineradicably altered the environment to the detriment of many other typical species.Animal life of particular interestAnimal life of particular interest to humans includes four main groups that are not mutually exclusive. They are: (1) species potentially or actually useful to humans as food (large ungulates), (2) dangerous or pest species that may have to be controlled or eliminated (locusts, tsetse flies, quelea finches or black-faced diochs—which do immense damage to grain crops—and some ungulates or carnivores), (3) species that provide a spectacle and bring economic benefit (elephants, the larger plain ungulates, primates, or carnivores), and (4) endangered, rare, or unique species.Much of the study of African wildlife has been addressed to the first two groups described above. For example, after it was learned that the feeding habits of domesticated livestock and wild ungulates are complementary, it became possible to incorporate the ungulates into pastoral and mixed-farming systems. This has happened on limited scales with the oryx (which was domesticated by the ancient Egyptians), the springbok (which has been run with cattle for decades in southern Africa), and the African buffalo (see photograph—>) and eland. Similarly, much attention has been given to controlling pests. In the 1950s and '60s considerable progress was made in the control of mosquitoes and locust swarms, although these achievements have been partially lost by governmental instability and mismanagement and by warfare between states. Infestation by the tsetse fly remains as one of tropical Africa's most critical problems, not only because the tsetse spreads disease but also because—by effectively restricting livestock farming—it denies relief of the chronic protein shortage of many African peoples. Control of the tsetse is possible, but it is complex and requires a coordinated effort within and between countries.Much research has also been carried out on animals in the third and fourth groups. Studies of predators, such as the lion, for example, have shown that they do not generally control the numbers of ungulates to the same degree as do disease or starvation. It has also been established that the hyena is as much a potent predator as a scavenger. Intensive studies have been made of such primates as baboons, Ethiopian geladas (to which baboons are related), and especially chimpanzees and gorillas; of great interest has been learning what associations there are between human and other primate behaviour and psychology.Many countries have now set aside large tracts as national parks (national park), game reserves, or forest reserves. Of these parks, only some are large enough to be self-contained ecosystems, and most have been set aside to accommodate large mammals. In East Africa there are also sanctuaries for birds and marine organisms. The conservation of vegetation is undertaken mainly in forest reserves but also in national parks. In addition, a number of countries are attempting to conserve wildlife by refusing export licenses for certain kinds of skins, especially those of the leopard, cheetah, and zebra.Conservation efforts in southern Africa have been aided by the creation of transfrontier parks and conservation areas, which link nature reserves and parks in neighbouring countries to create large international conservation areas that protect biodiversity and allow a wider range of movement for migratory animal populations. One such park is the Great Limpopo Transfrontier Park (GLTP), where representative populations of most savanna species are maintained. The GLTP links one of Africa's oldest and best-known national parks, Kruger National Park, with Mozambique's Limpopo National Park and Zimbabwe's Gonarezhou National Park. Another is Kgalagadi Transfrontier Park, which links South Africa's Kalahari Gemsbok National Park with Botswana's Gemsbok National Park; it conserves a tract of arid country with such associated types of antelope as springbok and gemsbok; smaller reserves and parks conserve particular species. Only one large mammal species, the blaubok (or blaauwbok), has become extinct, though several subspecies have nearly disappeared; one such subspecies—the quagga, a race of zebra—has vanished. East and central African countries have large national parks, which have been expanded in size or have increased in number as a result of the economic benefits of tourism. Kenya's parks include Tsavo, one of the largest, with an area of more than 8,000 square miles, Lake Nakuru National Park for flamingos, several montane parks, and a marine park. Uganda has several national parks. Tanzania has the famous Serengeti National Park, with its unrivaled populations of plains ungulates, and the parks of Ngorongoro, Lake Manyara, Arusha, and others. Other countries with notable national parks and game reserves are Botswana, Malaŵi, Namibia, Zambia, and Zimbabwe. All parks in these countries preserve representative woodland, thornbush, grassland, and succulent-desert habitats and species.Elsewhere the situation is less satisfactory. In Congo (Kinshasa), national parks were all seriously depleted after independence. Congo now has several major national parks, including the Virunga National Park (3,100 square miles), but in the late 20th century many suffered from deforestation and poaching, as well as general human encroachment, due to conflicts and warfare in the region. Though The Sudan (Sudan, The) is one of the countries with the largest numbers of remaining ungulates (ungulate), their status is little known, and the country is not served by an adequate park network. Ethiopia has several parks developed largely during the 1970s, while Somalia has only a rudimentary system consisting mostly of game reserves and one area (Luc Badana) nominally a national park but failing to meet UN criteria for such parks. The “W” park is shared between Burkina Faso, Niger, and Benin, but most West African countries have only small national parks if any at all.Animals not protected in parks are not necessarily threatened. Many large species are still plentiful in forest or game reserves or in controlled-hunting areas. Well-managed forest reserves in particular provide secure habitats for many smaller unprotected forms.Animals affecting land usageHistorically, the abundance of elephants and other large ungulates may have stimulated some individuals—notably West African hunters in the forests and Europeans in southern Africa—to occupy certain areas. Trade routes were established and early hunter-explorers were influenced by the availability of elephants, whose ivory tusks slaves could carry.Large and small animals now affect humans by competing with them or with their livestock. They may prey on people or on livestock or carry diseases affecting either. The bilharzia snail (snail) and the Simulium fly (host to an organism causing blindness), the tsetse fly, and the mosquito collectively affect human beings and their livestock far more than do such individually large or formidable species as lions or elephants.The larger ungulates may compete with domestic livestock for forage, but they are more keenly resented and hunted by those agriculturists whose crops they eat. Pastoralists are much more concerned about lions that occasionally kill cattle than they are about locusts or rats, which, by depleting forage, indirectly cause the death of much livestock; such perceptions may hinder eradication or better control of these pests.Danger to humans from large animals—carnivorous or otherwise—has been greatly exaggerated, but disease carried by living organisms has remained a serious problem. Diseases have reduced crop productivity, spoiled harvests, and acted as a curb on the better integration of land use and on the extension of pastoralism and mixed farming into underused areas.David N. McMasterThe people (Africa)Africa is now widely recognized as the birthplace of the Hominidae (the taxonomic family to which modern humans belong). Archaeological evidence indicates that the continent has been inhabited by humans and their forebears for some 4,000,000 years or more. Anatomically modern humans are believed to have appeared about 100,000 years ago in the eastern region of sub-Saharan Africa. Somewhat later these early humans spread into northern Africa and the Middle East and, ultimately, to the rest of the world.Africa is the most tropical of all the continents; some four-fifths of its territory rests between the Tropics of Cancer and Capricorn (Cancer and Capricorn, Tropics of). As a consequence, the cultures and the physical variations of the peoples reflect adaptation to both hot, dry climates and hot, wet climates. Dark skin is the dominant characteristic of indigenous African peoples, but skin colour is not uniform. Skin colour shows a clinal variation from a light or tan colour in the northern fringe of the continent, which has a Mediterranean climate, to very dark skin in certain Sudanic regions in West and East Africa, where radiation from the Sun has been most intense. Africa has the most physically varied populations in the world, from the tallest peoples to the shortest; body form and facial and other morphological features (morphology) also vary widely. It is the continent with the greatest human genetic variation, reflecting its evolutionary role as the source of all human DNA.Throughout human history there have been movements of peoples (see human migration) within, into, and out of Africa along its northern coasts, across the Sinai Peninsula, along the Red Sea, and especially in the Horn of Africa and coastal areas as far south as southern Africa. North Africa from the Straits of Gibraltar to the Nile River delta has been the site of conquests and movements of peoples for more than 3,000 years. Along the east coast, trading cities arose and fell, cities that had overseas contacts during the past two millennia with peoples of southern Arabia and as far east as India and Indonesia. Internal movements during this time contributed to the heterogeneity and complexity of native African societies. The greatest movement of peoples out of the continent was a result of the Atlantic slave trade that lasted from the 16th to the 19th century and saw an estimated 10,000,000 people transported into the New World. Such a loss of people, together with the devastating warfare and raiding associated with it, was the major cause of the subsequent weakness and decline of African societies.Whereas the majority of Africa's peoples are indigenous, European (Europe, history of) colonial settlers constitute the largest majority of new peoples, with substantial numbers in Kenya, South Africa, Zimbabwe, Zambia, Namibia, and Mozambique. Dutch settlers first arrived in South Africa in 1652; their descendants now constitute the main Afrikaner, or Boer, population. The vast majority of European settlers arrived after the 1885 Berlin West Africa Conference and the resulting “scramble for Africa,” during which European leaders carved out spheres of influence. Attendant, but unassociated, with the scramble, French and Italian settlers also established new communities in North Africa and, to some extent, West Africa. Much earlier, in several waves of migrations beginning in the 7th century, Arabs spread across northern Africa and, to a lesser extent, into West Africa, bringing a new religion (Islam) and a new language (Arabic), along with some new cultural and political institutions. They also spread Islam southward along the east coast, largely through trading and kinship relationships. (More detail is given in the regional history articles North Africa, Central Africa, Southern Africa, Western Africa (western Africa, history of), and Eastern Africa (eastern Africa, history of).)The colonial era began to disintegrate in the 1950s. At the end of the 20th century Africa included 47 independent nation-states (including island states), varying in size from São Tomé and Príncipe (with a population under 200,000) to Nigeria (with more than 140,000,000). Foreign-born populations are found in most states. The total population of the African continent was estimated to exceed 939,000,000 (2007 est.) in the first decade of the 21st century.Culture areasAlthough the precise number is unknown, there are several thousand different societies or ethnic groups (tribe) in Africa. They are identified by their recognition of a common culture, language, religion, and history. But in some areas the boundaries among ethnic groups and communities (villages, towns, farm areas) may not always be clear to the outsider. Most Africans speak more than one language, and frequent migrations and interactions, including intermarriage, with other peoples have often blurred ethnic distinctions. There are an estimated 900 to 1,500 different languages, but many distinct political units share a common or similar language (as among the Yoruba, Hausa, and Swahili-speaking peoples). Complicating this situation in the 20th century was the creation of new “tribes” (such as the Zande [Azande] and Luo) that had not been distinct polities before the colonial era. Ethnic (cultural) identities in modern times have often been heightened, exacerbated, or muted for political reasons.In their attempts to comprehend such a huge heterogeneous continent, scholars have often tried to divide it into culture areas that represent important geographical and ecological circumstances. These reflect differences in the cultural adaptation of traditional societies to varying natural habitats. For the purposes of this discussion, the principal regions are northern, western, west-central, eastern, and central and southern Africa; Madagascar is also included.Audrey SmedleyNorthern Africa (North Africa)Africa north of the Sahara is differentiated from the rest of the continent by its Mediterranean climate and by its long history of political and cultural contacts with peoples outside of Africa. It is physically separated from the rest of the continent by the Atlas Mountains and is inhabited primarily by peoples who speak languages that belong to the Afro-Asiatic (Afro-Asiatic languages) group. These peoples include, for example, the Imazighen (Berbers (Berber)) of Morocco, Algeria, and Tunisia. The Berbers are most numerous in Morocco and least in Tunisia, where, as a result of culture contact and intermarriage, they have become largely assimilated with Arabs (Arab), who speak a Semitic language. The Arabs migrated into North Africa from Arabia in a number of waves; the first of these waves occurred in the 7th century AD. The distinctive nature of Maghrebian (Maghrib), or western Arab, culture resulted from this admixture. In the Sahara such Arab peoples as the Shuwa live side by side with such Berber peoples as the Tuareg. See also Islamic world (Islāmic world).Western Africa contains a remarkable diversity of ethnic groups. It can be divided into two zones, the Sudanic savanna and the Guinea Coast (Guinea). The savanna area stretches over 3,000 miles (4,800 km) east to west along the southern Saharan borderland. Its vegetation consists of extensive grasslands and few forests, and little rain falls there. The savanna supports pastoralism and horticultural economies dependent on grain. In contrast, the Guinea Coast experiences heavy rainfall and is characterized by hardwood tropical forests and dense foliage. It produces primarily root crops (various yams).Among the more important of the savanna peoples are the three main clusters known as Mande in Senegal and Mali and including the Bambara, Malinke, and Soninke; the Gur-speaking group in the savanna zone to the east that includes the Senufo, Lobi, Dogon, and Moore; and in northern Nigeria, Niger, and Cameroon the many small, mainly non-Muslim tribes of the plateau and highland areas. Throughout this region live the many groups of the Fulani, a cattle-keeping Muslim people who either have conquered indigenous peoples (such as the numerous Hausa) or live in a symbiotic relationship with agricultural peoples. In the Sahara fringe are the many Berber-speaking groups (collectively known as the Tuareg), the Kanuri of Lake Chad, and the Bedouin Arab peoples. Many of the kingdoms are successor states to those of Ghana and Mali.The larger societies in the coastal zone are also mostly kingdoms. In Nigeria are the Igbo and Ibibio, organized into many autonomous polities; the Tiv; the Edo; and the several powerful kingdoms of the Yoruba. Westward are the Fon of Benin; the various peoples of the Akan confederacy, mostly in Ghana, the largest group being the Asante; the Ewe, Ga, Fante, and Anyi of the coast; the Mende and Temne of Sierra Leone; the Kru of Liberia; the Wolof, Serer, Dyula, and others of Senegal; and the Creoles of Sierra Leone and Liberia, descendants of freed slaves from the New World or of those who were on their way there.West-central AfricaWest-central Africa may be considered as an eastern extension of western Africa: in the north are the savannas of Chad, the Central African Republic, and The Sudan, stretching to the Nile River, and in the south is the largely forested area of the Congo River basin. The Congo area, in the centre of the continent, is an extension of the wet forestlands of the Guinea Coast; it extends to the lacustrine area of eastern Africa. This region is the largest area of secondary tropical forest in the world; only South America has more primary (i.e., undisturbed by humans) tropical forests. The vast majority of peoples speak related languages of the Bantu family. The Luba, Lunda, Fang, Mongo, Kuba, Songe, and Chokwe are among the larger ethnic groups of west-central Africa. The Bambuti (Pygmy) peoples live in the eastern forests, and smaller groups of Pygmy peoples live in the western forests of Gabon.Eastern Africa can also be divided into several regions. The northern mountainous area, known as the Horn of Africa, comprises Djibouti, Ethiopia, Eritrea, and Somalia. In the east is the arid Somali desert. The coastal area extends from Kenya to southern Africa, where numerous trading cities arose beginning in the 10th century. The East African Rift System intersects eastern Africa, running from north to south. This region, particularly the areas of the East African lakes—Victoria, Albert, Tanganyika, and Nyasa (Malaŵi)—contains some of the most fertile land in Africa, and during the colonial period it attracted settlers from Europe and Asia. Vast areas of savanna support pastoralists and peoples with mixed economies.Ethnically complex, eastern Africa includes the Eastern Sudanic-speaking pastoralists of the Nile valley (Shilluk, Dinka, Luo, Lango, and others), those of the central plains (Masai, Nandi, and others), and the Somali and Oromo of the Horn of Africa, who speak Cushitic languages. In Ethiopia also are the Amhara, Tigre, and others who speak Semitic languages. Most of the remaining peoples of the region are Bantu speakers who, although they vary widely in other ways, are all subsistence farmers. Near the East African lakes are several formerly powerful Bantu kingdoms (Ganda, Nyoro, Rwanda, Rundi, and others). In the highlands of Kenya are the Kikuyu, Luhya, and others. On the coast are the various Swahili-speaking tribes, while in Tanzania are the Bantu-speaking (Bantu peoples) Chaga (Chagga), Nyamwezi, Sukuma, and many more. There are also remnants of other groups: the hunting Okiek (Dorobo), Hadza, and some Pygmies. And on the coast are the remnants of the once politically powerful Arabs, formerly based on Zanzibar.Central and southern Africa may be considered as a single large culture area. Most of it consists of open and dry savanna grasslands: the northwest contains the edges of the Congo forests; the southwest is very arid; and the coastline of South Africa and Mozambique is fertile, most of it with a subtropical or Mediterranean climate.The region was once populated by Khoisan-speaking peoples. The San are today restricted to the arid areas of southwestern Africa and Botswana, and most of the Khoekhoe are found in the Cape region of South Africa. The other indigenous groups are all Bantu-speaking peoples, originally from the area of Cameroon, who dispersed across this region some 2,000 years ago. The vanguard, known linguistically as the Southern Bantu, drove the Khoekhoe and San before them and adopted some of the typically Khoisan click sounds into their own languages. Over the past several hundred years, Bantu-speaking people who had mixed economies with large numbers of cattle began massive movements, mostly northward. A major cause of this displacement of peoples (which together with a series of related wars is known as the Mfecane) was the search for new grazing lands. A number of conquests resulted in the establishment of the states of the Zulu, Swazi, Tswana, Ndebele, Sotho, and others.The island of Madagascar forms a distinct culture area. The various Malagasy ethnic groups, of which the politically most important is the Merina, are mainly of Indonesian origin, following migrations across the Indian Ocean probably during the 5th and 6th centuries AD. The Malagasy language (Malagasy languages), spoken by 98 percent of the island's population, is classified as Austronesian (Austronesian languages).John F.M. Middleton John Innes Clarke Audrey SmedleyCultural patternsLanguagesThe knowledge of most of the individual languages of Africa is still very incomplete, but there are known to be in excess of 1,500 distinct languages. Many attempts to classify them have been inadequate because of the great complexity of the languages and because of a confusion relating language, “race,” and economy; for example, there was once a spurious view of pastoralism as related to cultures whose members spoke “Hamitic” languages and were descendants of ancient Egyptians. One of the more recent attempts to classify all the African languages, prepared by the American linguist Joseph Greenberg (Greenberg, Joseph H.), is based on the principles of linguistic analysis used for Indo-European languages rather than on geographic, ethnic, or other nonlinguistic criteria. The four main language families, or phyla, of the continent are now considered to be Niger-Congo (Niger-Congo languages), Nilo-Saharan (Nilo-Saharan languages), Afro-Asiatic (Afro-Asiatic languages), and Khoisan (Khoisan languages).Niger-Congo (Niger-Congo languages) is the most widespread family and consists of nine branches: Kordofanian (Kordofanian languages), Mande, Ijoid, Atlantic, Benue-Congo, Kru, Kwa, Gur, and Adamawa-Ubangi. These languages cover most of central and southern Africa; they are found from Senegal to the Cape of Good Hope, with a geographically widespread extension due to relatively recent migrations. Kordofanian includes subgroups all spoken within a small area of central Sudan. The most original point in this classification is the group called Benue-Congo (Benue-Congo languages), which linguistically subsumes all the Bantu languages found dispersed over most of eastern, central, and southern Africa. This dispersal is attributable to the rapid expansion of people from the area of the Bight of Benin from the beginning of the 2nd millennium AD onward: the vanguard, the Southern Bantoid speakers, had not reached the Cape of Good Hope when the Dutch arrived there in the 17th century. The close linguistic similarity among the Bantu languages points to the speed of this vast migration. Swahili (Swahili language), grammatically Bantu but with much Arabic in its vocabulary, is widely used as a lingua franca in eastern Africa; as the language of the people of Zanzibar and the east coast, it was spread by 19th-century Arab slavers in the hinterland as far as what is now the Democratic Republic of the Congo. Fula, an Atlantic language of the Niger-Congo family, also is used as a lingua franca in West Africa.The Nilo-Saharan (Nilo-Saharan languages) family classification is perhaps the most controversial—because of inadequate research—and the family is the most scattered. It comprises languages spoken along the savanna zone south of the Sahara from the middle Niger to the Nile, with outlying groups among the pastoralists of eastern Africa. Its subgroups are Songhai, Saharan, Maban, Fur, Eastern Sudanic, Central Sudanic, Kunama, Berta, Komuz, and Kadu.The Afro-Asiatic (Afro-Asiatic languages) family includes languages from both Africa and the Middle East: Semitic (including Arabic, Amharic, and Tigrinya), Egyptian (extinct), Amazigh (Berber), Cushitic, Chadic (e.g., Hausa), and Omotic. It is found over much of northern Africa and eastward to the Horn of Africa. Arabic is both an official and an unofficial language in states north of the Sahara, as well as in The Sudan. In many other countries it is the language of Islam. Amharic is one of the two principal languages of Ethiopia. Hausa also is spoken widely as a lingua franca along the northern fringe of sub-Saharan West Africa, a wide area that encompasses many ethnic and political boundaries.The Khoisan (Khoisan languages) family comprises the languages of the aboriginal peoples of southern Africa, who now are limited largely to the arid parts of southwestern Africa, and perhaps of the outlying Hadza and Sandawe peoples of northern Tanzania.The Austronesian (Austronesian languages) language family is represented by the various languages of Malagasy (Malagasy languages) in Madagascar.There are many widespread trade languages and lingua francas (lingua franca) in addition to those mentioned above. Some, including English and French, were imported and used by administrators, missionaries, and traders during the colonial period. Some of these have become the national languages of independent nation-states, and, with the spread of formal education, they are gaining greater acceptance. Between the Sahara and the Zambezi River, either English (English language) or French (French language) is widely understood. French is an official language in the states that formerly made up French West Africa and French Equatorial Africa, as well as in Madagascar (Malagasy is also an official language) and Congo (Kinshasa). Similarly, English is the official language or is widely spoken in the states of western, central, and eastern Africa formerly under British administration and is also the official language in Liberia. Portuguese (Portuguese language) is used officially and otherwise in the countries formerly under Portugal. In South Africa, English and Afrikaans (Afrikaans language) (which developed from 17th-century Dutch (Dutch language) by way of the descendants of European [Dutch, German, and French] colonists, indigenous Khoisan-speaking peoples, and African and Asian slaves) are among the many official languages. Hindi, Gujarati, Urdu, and other languages of the Indian subcontinent are spoken in the Asian communities. In West Africa, forms of creole (creole languages) (Krio) and pidgin are widespread in the coast towns of very heterogeneous ethnic composition. In southern Africa, Fanagalo, a mixture of English and local Bantu tongue (notably Zulu), is still spoken in some mining areas.The great majority of African languages have no indigenous forms of writing. Several of these, however, were transcribed in the 20th century by missionary linguists, native speakers, and others. Many African languages (such as Swahili) have for centuries been written in Arabic script (Arabic language). The best-known exceptions to the Arabic writing system are those of the Vai of Sierra Leone, the Mum (Bamum) of Cameroon, and the Tuareg and other Berber groups of the southern Sahara, all of whom invented their own scripts.Religions (Africa)In general, northern Africa is predominantly Islamic (Islāmic world) and southern Africa largely Christian (Christianity), although their distributions are not discrete. For example, the Coptic church is found in Egypt and Ethiopia, and Islam is common along the coast of eastern Africa and is expanding southward in western Africa. Many of the Sudanic (Sudan) peoples—such as the Malinke, Hausa, Songhai, and Bornu—are Islamized, and the religion has also achieved substantial gains among such Guinea Coast people as the Yoruba of Nigeria and the Temne of Sierra Leone. Much conversion to Christianity also has occurred, most notably to Roman Catholicism and in the coastal regions of sub-Saharan Africa.In most of the rest of sub-Saharan Africa the people practice a variety of traditional religions, which have certain common features. All of those known include the notion of a high or creator God, remote from humans and beyond their comprehension or control. This God typically is not attributed a sex but in some cases is male or female; often God is given an immanent and visible aspect as well. The most important “spiritual” powers are usually associated with things or beings with which people have day-to-day contact or that they know from the past. Thus, there may be many kinds and levels of spirits of the air, of the earth, of rivers, and so on. There may be ancestors and ghosts of the dead who have achieved a partial divinity, or there may be mythical heroes who led the people to their present land and founded their society as it is known today.The ritual functionaries (ritual) found in most African societies include priests, lineage and clan elders, rainmakers, diviners, prophets, and others. Very few of these are specialists; typically they hold ritual authority by virtue of age, genealogy, or political office and are primarily responsible for the ritual well-being only of the members of the social groupings that they head; their congregations consist of their joint families, lineages, clans, local village communities, chieftaincies, or the like. Their ritual authority is thus a sanction for their secular and domestic authority.A central element of every indigenous African religion is its cosmology—which tells of tribal origins and early migrations and explains the basic ideological problems of any culture, such as the origin of death, the nature of society, the relationship of men and women and of living and dead, and so on. Social values are typically expressed in myths, legends, folktales, and riddles; the overt meanings of these various oral statements frequently conceal sociological and historical meanings not easily apparent to outsiders.In the past, witchcraft and sorcery were given widespread credence and served to explain or control the misfortunes of people who were aware of their lack of mastery and understanding of nature and society. Travelers' tales of African people living in fear of witchcraft, however, were, of course, grossly exaggerated; the colonial powers usually assumed (incorrectly) that witch doctors were socially harmful and prohibited them. Although belief in witchcraft is receding, it is still important in both rural and urban areas, often serving as a means of explaining the misfortunes that beset urban dwellers and labour migrants who find themselves in new and confusing social milieus. There have been many cases in modern times of “epidemics” of beliefs in witches, and there have arisen a number of evanescent religions led by various kinds of prophets and evangelists. Such manias arise in periods of radical change and their resultant uncertainty and stress.Social and religious changes in Africa have often been accompanied by the appearance of prophets who advocate the expulsion of the Europeans or the eradication of epidemic diseases threatening the traditional ways of life. More recently, also, the spread of Christianity and, to a lesser extent, Islam has given rise to Christian prophets and to leaders of separatist movements repudiating European-controlled mission churches for nationalistic, tribalistic, or racial reasons. Such prophets lead their own groups and establish their own churches, typically gaining new political power sanctioned by their presumed direct links with God. These new churches have been reported in almost all parts of the continent.Domestic groupingsThe forms of the family found in Africa are consistent with the forms of economic production. Throughout most of the rural areas the typical domestic group is the joint or extended family consisting of several generations of kin and their spouses, the whole being under the authority of the senior male. The size of the group varies, but it typically consists of three to five generations of kin. It provides a stable and long-lasting domestic unit able to work as a single cooperative group, to defend itself against others, and to care for all of its members throughout their lifetimes. polygyny is traditionally widespread as an ideal, its extent depending on the status and wealth of the husband: chiefs and rulers need many wives to give them a mark of high position and to enable them to offer hospitality to their subjects.In most of Africa these residential groups are based on descent groups known as clans and lineages, the latter being segments of the former. The significance given to descent groups varies, but they are important in providing for heirs, successors, and marital partners.In the second half of the 20th century this pattern began to change—rapidly in the urban and poverty-stricken areas, more slowly in those areas less affected by economic and political development. In cities and in major labour-supplying areas, such as most of southern Africa, the joint or extended family gave way to the independent nuclear family of husband, wife, and children. There is also a tendency toward the breakdown of family structure because of labour migration—the younger men moving to the cities, leaving women, older men, and children in the impoverished homelands.John F.M. Middleton John Innes Clarke Ed.Demographic patternsAfrica has the most rapidly expanding population of any region in the world, even though the continent's birth and death rates are also the world's highest. There was some decline in overall death rates in the latter half of the 20th century; but infant and child mortality rates remained high, and average life expectancy at birth actually declined somewhat during the 1990s. On average, Africa's population is increasing at about 3 percent per annum, and this growth rate is associated with an increasingly youthful population: in nearly every African country more than two-fifths of the population is less than 15 years of age.The great majority of the working population is still engaged in subsistence agriculture and in the production of cash crops. In most countries the proportion of the total population dependent on agriculture is at least three-fifths.The remainder of the working population is divided mainly between a rapidly growing service sector (including civil servants, members of the armed forces, police, teachers, health workers, and those engaged in commerce and communications) and an increasing number of mining and industrial projects; in only a few countries, however, do these latter activities employ more than one-tenth of the workforce. Underemployment, particularly in the agricultural sector, is widespread, and unemployment has risen, especially in urban areas. Participation in labour by women varies considerably from country to country. There are generally fewer women in paid employment than men, though a large proportion of women in sub-Saharan countries are engaged in subsistence agriculture—if only part of the time. Women are also employed in the civil service, trading (especially in western Africa), domestic service, and to an increasing extent in light industry.Population distributionAfrica has more than one-eighth of the total population of the world, distributed over a land area representing slightly more than one-fifth of the land surface. Such desert areas as the Sahara, Kalahari, and Namib, however, have reduced the amount of habitable land, and such factors as climate, vegetation, and disease have tended to limit the evolution of densely populated areas where agriculture is practiced. With the advent of the colonial era, the African continent was divided into small geographically and politically based units that took little or no account of ethnic distribution. These political boundaries persisted, and the continent continued to be characterized by a large number of countries with predominantly small populations.Wide variations in density occur from country to country in Africa and within countries. In general, the most densely populated areas are found bordering the lakes, in the river basins (especially those of the Nile and Niger), along the coastal belts of North and West Africa, and in certain highland areas, while settlement is the most sparse in the desert and savanna areas. Thus, Rwanda and Burundi, situated in the East African highlands, are the most densely populated countries in Africa, while Western Sahara, Mauritania, and Libya in the Sahara and Botswana and Namibia in the Kalahari and Namib are the least densely populated.Settlement patternsTraditional African patterns of settlement vary with differences in landscape and ecology, communications, and warfare. The most widespread pattern has been that of scattered villages and hamlets—the homesteads of joint and extended families—large enough for defense and domestic cooperation but rarely permanent because of the requirements of shifting cultivation and the use of short-lived building materials. Large mud-adobe villages are traditional in much of the western African savanna, but over most of Africa housing consists of mud and wattle with roofs of thatch or palm leaves.Large towns were not widespread in the continent until the 20th century. Towns dating from precolonial times are found mainly along the Nile valley and the Mediterranean fringe of North Africa—where many date from classical times (e.g., Alexandria, Egypt) and the late 18th century (e.g., Fès, Morocco)—and also in western Africa, in both forest and savanna zones, where they were the seats of governments of kingdoms. Timbuktu, Ife, Benin City, and Mombasa all date from the 12th century, while the city of Kano has prehistoric origins. Ibadan and Oyo became important cities only in the 19th century.The more traditional towns differ in form, function, and even population characteristics from the many towns and cities established under colonial rule as administrative, trading, or industrial centres and ports. These latter cities are found throughout Africa and include Johannesburg, Lusaka, Harare, Kinshasa, Lubumbashi, Nairobi, Dakar, Freetown, Abidjan, and many others; often, as in the case of Lagos or Accra, they are built onto traditional towns. Typically the focus of in-migration from an impoverished hinterland, they are ethnically heterogeneous. Many have grown to become the largest cities in their respective countries, dominating their national urban hierarchies in size as well as in function.Mostly rural for centuries, Africa has rapidly become more urbanized. Although it is still the least urbanized of the continents, Africa has one of the fastest rates of urbanization. Thus, the total population living in towns—which was only about one-seventh in 1950—grew to about one-third by 1990 and was approaching two-fifths in the year 2000. Generally, the level of urbanization is highest in the north and south, and it is higher in the west than in the east and nearer the coasts than in the interior.The largest cities include Cairo, Alexandria, and Al-Jīzah, Egypt; Kinshasa, Congo; Lagos, Nigeria; Casablanca, Morocco; Johannesburg, South Africa; Addis Ababa, Ethiopia; and Algiers, Algeria. Many other large cities are seaports along the coasts or central marketing towns, linked by rail or river with a coast. Examples of seaports are Accra, Ghana; Lagos; and Cape Town, South Africa. Ibadan and Ogbomosho, Nigeria; Nairobi, Kenya; and Addis Ababa are examples of large inland cities.MigrationsThere have been many movements of population within the African continent, from outside into the continent, and from the continent outward. The major movement within the continent in historic times has been that of the Bantu-speaking (Bantu peoples) peoples, who, as a result of a population explosion that is not fully understood, spread over most of the continent south of the Equator.The major movements into the continent in the past few centuries have been of European settlers into northern Africa and of European and Asian settlers in southern Africa. The Dutch migrations into southern Africa began in the mid 17th century. Originally settling on the coast, the Dutch—or Boers (Boer)—later moved inland to the Highveld region, where a series of military conflicts occurred between them and the Bantu (Bantu peoples) speakers in the 19th century. Other European settlement took place mainly in the 19th century: the British particularly in what is now KwaZulu-Natal province of South Africa but also inland in what are now Zambia and Zimbabwe and in the East African highlands, the Portuguese in Angola and Mozambique, and the Germans in what is now Namibia.The presence of large settler populations delayed the achievement of self-government by the African peoples of South Africa, Namibia, Zimbabwe, Angola, and Mozambique and has resulted in much bitterness between the indigenous peoples and settlers. In North Africa, by contrast, where the extensive settlement of Europeans from France, Italy, and Spain occurred, the growth of Arab nationalism and the emergence of independent states such as Morocco, Algeria, and Tunisia led to the return of between one and two million colonists to their homelands in the late 1950s and early 1960s and to the political dominance of the indigenous peoples.The greatest outward movement of people was that of Africans—particularly from West Africa and, to a lesser extent, Angola—to the Americas and the Caribbean during the period of the slave trade (slavery) from the 16th to the 19th century. (For further discussion of this phenomenon, see slavery.) Earlier estimates that between 15 and 20 million Africans were transported across the Atlantic have been revised to a figure of 10 million, which appears more realistic. While their contribution to the development of the New World was of crucial importance, the effect of the loss of manpower to the African continent was considerable and has yet to be satisfactorily analyzed. The slave trade was also active on the east coast of Africa, where it was centred on the island of Zanzibar.There were few permanent population movements in Africa during the 20th century, although an extensive settlement of Hausa from northern Nigeria took place in what is now The Sudan. Warfare produced some significant population displacements, usually of minority groups fleeing the dominant majority. In 1966 the Igbo people of northern Nigeria, for example, returned en masse to their homeland in eastern Nigeria, the number of refugees being estimated at more than 500,000. The conflicts in the Horn of Africa since the 1960s have caused similar displacements. Indeed, Africa has millions of refugees, especially from Burundi, Somalia, and The Sudan. These refugees are among the poorest and most vulnerable people in the world, and their numbers are substantially augmented by those fleeing drought and famine. The countries to which these people flee often find it extremely difficult to cope with them.Most movement occurs across uncontrolled borders and between people of the same tribal groups. Much is seasonal, in any case, and is restricted to migrant labourers and nomadic herdsmen. Controlled immigration and emigration are generally negligible; contemporary examples, however, include the employment of mine workers in South Africa, the forced emigration of Asians from East Africa, and the expulsion of people from neighbouring West African states caused by such actions as the enforcement of the Alien Compliance Order of 1969 in Ghana.The economyWith the exception of South Africa and the countries of North Africa, all of which have diversified production systems, the economy of most of Africa can be characterized as underdeveloped. Africa as a whole has abundant natural resources, but much of its economy has remained predominantly agricultural, and subsistence farming still engages more than 60 percent of the population.Until the beginning of the 20th century this system of farming relied on simple tools and techniques, as well as on traditional organization of the family or community for its labour. Because of poor transport and communications, production was largely for domestic use. There was little long-distance trade, and wage labour was virtually unknown. The small size and vast heterogeneity of polities at that time also made exchanges very limited. There were, however, notable exceptions, especially in West Africa, where for many centuries societies had engaged in long-distance trade and had elaborate exchange and craft facilities, communications, and a political infrastructure to maintain their trade routes.Africa has experienced considerable economic development during the 20th century; and, while this has provided many benefits, it also has given rise to a number of serious problems. The first significant changes occurred under colonial rule in the first half of the century: wage labour was introduced, transportation and communications were improved, and resources were widely developed in the colonial territories. The legacy of this, however, has been that the export of two or three major agricultural products or minerals—such as peanuts, petroleum, or copper—has come to provide most of the foreign-exchange earnings for nearly all African nations. Fluctuations in the prices of these commodities have made the economies of these countries vulnerable and fragile. The situation has been exacerbated in countries in the marginal dryland zones, where the increasing frequency of drought conditions have undermined agricultural productivity.The second major change was the vigorous promotion of industrial development, often with foreign assistance, that took place in the two decades (1960–80) following the political independence of most African countries. The political fragmentation of the continent, however, also became a major constraint to industrial growth, because it created numerous small markets. Consequently, most African countries have become saddled with excess industrial capacity, coupled with enormous foreign debts that were incurred in large part to build this capacity.In nearly all African countries a poor economic situation has been aggravated by rapid population growth, which has kept per capita gross domestic product low or in some cases has caused it to decline. Thus, any hope for improving economic conditions in most of Africa rests on two factors: population control within individual countries to give their economies the chance to grow; and the organization of groups of states into regional economic blocs in order to create internal markets large enough to sustain growth.ResourcesMineral resourcesAfrica's known mineral wealth places it among the world's richest continents. Its very large share of the world's mineral resources includes coal, petroleum, natural gas, uranium, radium, low-cost thorium, iron ores, chromium, cobalt, copper, lead, zinc, tin, bauxite, titanium, antimony, gold, platinum, tantalum, germanium, lithium, phosphates, and diamonds.Major deposits of coal are confined to four groups of coal basins—in southern Africa, North Africa, Congo (Kinshasa), and Nigeria. Proven petroleum reserves in North Africa occur in Libya, Algeria, Egypt, and Tunisia. Exploration has been concentrated north of the Aïr–Ahaggar massifs; there may also be major Saharan reserves to the south. The other major oil reserves are in the West African coastal basin—mainly in Nigeria and also in Cameroon, Gabon, and Congo (Brazzaville)—and in Angola. Africa's natural gas reserves are concentrated in basins of North and coastal central Africa.Southern Africa is said to be one of the world's seven major uranium provinces. In South Africa the unusual degree of knowledge of reserves derives from the joint occurrence of uranium with gold, a condition that also decreases the cost of production. Other countries with significant uranium deposits are Niger, Gabon, Congo (Kinshasa), and Namibia.Metallic depositsIn North Africa reserves of iron ore are concentrated in the Atlas Mountains and in western Sahara. Egypt, however, has medium-grade reserves, of which the most important are at the Al-Wāḥāt al-Baḥrīyah Oasis. The ore deposits in Morocco and Tunisia, which were once of considerable importance, have been severely depleted. Africa's most significant iron reserves are to be found in western and southern Africa. It is the sedimentary Precambrian rocks, particularly in western Africa, that have proved the basis of Africa's role as a major world producer of iron ore. The most significant deposits are in Liberia in the Bomi Hills, Bong and Nimba ranges, and the Mano valley; in the extension into Guinea of the Nimba–Simandou ranges, where hematites have been located; in Nigeria and Mauritania, which have large deposits of low-grade ore; and in Gabon, where extensive reserves are present in the northeast. In southern Africa most iron ore reserves lie in South Africa itself. The chief deposits are at Postmasburg, in the Bushveld Complex, at Thabazimbi, and in the vast, low-grade deposits of Pretoria. There are also substantial reserves in Zimbabwe.Africa's reserves of minerals used as ferroalloys in the steel industry are even more striking than its enormous share of world iron ore reserves. This is particularly true of chromium. Almost the entire world reserve of chromium is found in southern and, to a much lesser extent, in western and northeastern Africa. The highest concentrations are found in Zimbabwe, at Great Dyke. South Africa contains the largest deposits of chromite. As compared with these two sources, reserves elsewhere in Africa are relatively small.manganese reserves are also considerable. In South Africa reserves of contained manganese are found in the Kalahari Manganese Field and elsewhere. The Mouanda deposit in southeastern Gabon is thought to be among the largest in the world. Ghana is another important source of manganese, having both low-grade and high-grade reserves. Elsewhere in West Africa, manganese deposits are situated in Burkina Faso and Côte d'Ivoire, as well as in Congo (Kinshasa) and Cameroon. In North Africa manganese is found in Morocco and Algeria.Africa's contribution to world resources of other ferroalloys is, by comparison, insignificant. Nickel is of some importance, occurring in other metalliferous ores in southern Africa.Most of Africa's copper is contained in the Central African Copperbelt, stretching across Zambia and into the Katanga (Shaba) area of Congo (Kinshasa). Accompanying minerals vary with the geologic layer, but cobalt dominates. Outside the Copperbelt a number of countries have lesser but still significant reserves of copper.Only Nigeria, Congo (Kinshasa), and South Africa contain tin reserves of any significance. Although it is difficult to consider Africa's reserves of lead and zinc separately, of the two, lead ores are considerably more widespread. North Africa is the largest traditional producing region. African reserves of zinc metal are located along the Moroccan-Algerian frontier, in the Copperbelt in Congo, in Nigeria, in Zambia, and in Namibia.Africa has about one-fourth of the world's reserves of bauxite, the chief aluminum ore. Virtually all of this occurs in a major belt of tropical laterite stretching some 1,200 miles from Guinea to Togo. The largest reserves are in Guinea.Half of the world reserves of cobalt can be found in Congo (Kinshasa) (Congo). A continuation of the geologic formation into Zambia gives the country sizable reserves of cobalt content. The only other deposit of any importance is found in Morocco.The titanium ores, ilmenite and rutile, are widely distributed in Africa but are rarely considered as minable reserves. A major source is the Sherbro deposit in Sierra Leone. Almost all of Africa's antimony resources lie in the Murchison Range of South Africa. The major concentrations of beryllium are in Madagascar, Mozambique, Congo (Kinshasa), Zimbabwe, Rwanda, Uganda, and South Africa. The principal sources of cadmium are in Namibia and Congo. Deposits of mercury are restricted to North Africa, notably to Tunisia and, more particularly, Algeria.gold and allied metals are widely disseminated, reaching their greatest concentrations in South Africa, where reserves of gold probably constitute about half of the world total. Gold is also found in Zimbabwe, in the Congo (Kinshasa) belt, and in Ghana. There are numerous alluvial sources of gold in Burundi, Côte d'Ivoire, and Gabon. South Africa has the most important deposit of platinum of the world's market economies. Silver reserves of the continent are not important.Africa contains a major share of world reserves of tantalum, with Congo (Kinshasa) having most of these reserves. African reserves of columbium, or niobium (a steel-gray metallic element resembling tantalum in its chemical properties that is used in alloys), are relatively small. Nigeria, however, is an important world producer.One of Africa's many sources of zirconium (a metallic element resembling titanium chemically) is the Jos Plateau in Nigeria. Greater reserves, however, are contained in deposits on the Senegal coast; on the east coast of South Africa; in Madagascar; at Sherbro, Sierra Leone; and in the Nile delta.Another rare metal of which Africa contains a majority of world reserves is germanium, concentrated in Congo (Kinshasa) and Namibia. Africa also has large deposits of lithium, the largest of which are found in Congo.Nonmetallic depositsClays are widespread and are found in North Africa, where brick and pottery clays occur in Algeria and in Morocco; in West and central Africa, where clays are located in Togo (ceramic), the Central African Republic, and Côte d'Ivoire (ceramic); and in East and southern Africa.Kaolin (china clay) occurs in Algeria. Outside North Africa it is widespread. In West Africa it occurs most notably in Nigeria's Jos Plateau, as well as in Mali, in Ghana, and in Guinea. Similar deposits occur in central and East Africa, as well as in southern Africa.Bentonite (a clay formed from decomposed volcanic ash, which is able to absorb large quantities of water and to expand to several times its usual size) is found in the Moroccan Atlas Mountains and in Tanzania, Kenya, and South Africa. The continent's principal reserve of fuller's earth (an absorbent clay) is in Morocco.Economically important mica deposits occur primarily in southern Africa (South Africa, Zimbabwe, and Tanzania) and in Madagascar.Africa has none of the world's major reserves of sulfur. It reaches economic concentrations only in South Africa's Witwatersrand, in Zambia's Copperbelt, and in Morocco. Large quantities of sodium deposits remain to be evaluated. Sodium chloride is the principal salt, the largest deposit being in the Danakil Plain of Ethiopia. The principal sources of salt in Africa, however, are inland or coastal basins, from which it is extracted by the evaporation of saltwater. Major coastal reserves of this type lie along the North African Mediterranean coast and along Red Sea and Indian Ocean coasts of East Africa and Madagascar. Inland, the chief reserves are in the Oran Sebkha, a salt-pan region in Algeria; in Botswana around Lake Makarikari; and in Uganda.Another important sodium mineral is natron, or sodium carbonate. Natron is more limited in occurrence, but Africa contains several significant deposits. It is found in Lake Magadi, Kenya, and in Lake Natron, Tanz., as well as in western Africa, where beds have been deposited from the waters of Lake Chad.North Africa has been a traditional exporter of phosphates (phosphate mineral), and western Africa has large reserves. Morocco and Western Sahara together have vast reserves. The Río de Oro region in Western Sahara contains huge deposits, and a major development at Bu-Craa has been established. Algeria and Tunisia also have reserves. To the east, phosphate-bearing sediments outcrop on the Red Sea coast. The Thiès deposit in Senegal is of particular interest in constituting the world's only source of aluminum (as opposed to calcium) phosphate. Other phosphate deposits occur in Togo, Nigeria, Tanzania, Uganda, and Malaŵi.The potash deposits in Congo (Brazzaville) are the largest in Africa. The other large reserve is in Ethiopia.Madagascar has the world's largest known accumulation of flake graphite deposits. Continuations of these high-quality deposits in Mozambique and southeastern Kenya contain further reserves of graphite.While deposits of low-grade sand suitable for construction and engineering work are widely distributed, reserves of sands with a sufficiently high silica content for glass manufacture are more localized. There are deposits in West Africa (Côte d'Ivoire, Liberia, Nigeria, and Ghana), East Africa (Uganda and Tanzania), and South Africa. Glass sands are also found in Egypt.Kyanite (cyanite), a mineral aluminum silicate used as a refractory, occurs most typically in southern Africa. Apart from South African reserves, there are deposits in Kenya, Malaŵi, Ghana, Cameroon, and Liberia.Of the abrasive substances, industrial diamonds (diamond) are most closely associated with Africa. The continent contains some 40 percent of the total world reserves. The stones are found in a number of major belts south of the Sahara. The principal known reserves of diamonds in their primary form are in the South African Vaal belt. Elsewhere in Africa, primary deposits are found in Tanzania, Botswana, and Lesotho.Another major belt of diamondiferous rocks encircles the Congo River basin and includes the world's largest deposit, located in Congo (Kinshasa), which contains the majority of Africa's reserves of industrial diamonds. The same belt has secondary deposits that occur elsewhere in that country, as well as in the Central African Republic and Angola. In West Africa known reserves are located primarily in alluvial gravel fields. They are found in Sierra Leone, Guinea, Côte d'Ivoire, Liberia, and Ghana.A considerable proportion of the world reserves of corundum (a common mineral, aluminum oxide, notable for its hardness) is located in southern Africa. The principal deposits are in Zimbabwe, South Africa, Mozambique, Madagascar, and Malaŵi.pumice is found in areas of volcanic activity such as the Atlantic islands, the coastal Atlas Mountains of northeastern Morocco, and in the East African Rift System, notably in Kenya, Tanzania, and Malaŵi. Joint reserves constitute, however, only a small percentage of the world total.Reserves of building materials are characterized by their wide distribution, to such an extent that the commercial status of such deposits depends more on their location relative to areas of development than on their extent and quality. While almost all African countries have reserves of building materials, knowledge of such reserves is strictly related to the country's level of development, and no meaningful estimate of the size of reserves can be made.granite is located in Morocco and Nigeria, and there are vast reserves in Burkina Faso. Quartzite (a granular rock, consisting essentially of quartz) is important as a building stone in Uganda and Congo (Kinshasa). Dolerite (a coarse-grained basalt) is produced in South Africa, and basalt, which is crushed for use in road construction, in Senegal. Marble is found in Mali, Togo, Nigeria, and South Africa.limestone is important because of its use in the cement industry, and deposits are fairly widespread. North Africa is a particularly important source. In western Africa a belt of limestone runs from the Central African Republic to the Atlantic coasts, with major outcrops in northern Nigeria, Niger, Burkina Faso, and Mali. Elsewhere there are deposits in Nigeria, Benin, Togo, and Ghana. East African deposits include those in Kenya, Tanzania, Uganda, and Zambia; there are also deposits in South Africa.North Africa has major reserves of gypsum on the Mediterranean coast, as well as in outcrops along the Gulf of Suez and the Red Sea. Somalia has one of the largest known deposits. Eastern Africa and Madagascar have further reserves, and in southern and western Africa superficial deposits are particularly important—for instance, north of Nouakchott, Mauritania.Many of the major deposits of the most important commercial gem mineral, the diamond, have already been described above in the discussion of industrial diamonds. One major deposit, however—that of Namibia—consists almost entirely of gem diamonds.There is no other gem mineral in Africa of comparable importance to these diamond reserves. Deposits of a number of such stones are found, however, especially in southern and eastern Africa, where diamond fields contain beryl, garnets, amethyst, rose quartz, topaz, opal, jasper, emeralds, and other stones. Madagascar contains a large deposit of garnet. Tourmaline is found in Madagascar and Namibia. Agate is particularly associated with the volcanic areas of eastern and southern Africa and malachites with the Katanga Copperbelt, while sapphires are found with diamonds in Ghana.Africa contains no major world deposits of talc, but the mineral is found in Morocco, Nigeria, The Sudan, Zimbabwe, and South Africa. Reserves of asbestos are much more important, and southern Africa has a number of deposits of world significance.Major deposits of fluorite, or fluorspar (a common mineral, calcium fluoride, used as a flux in metallurgy), are particularly associated with deposits of lead and zinc. In South Africa the chief deposit is in the Transvaal. North African reserves lie primarily in Tunisia and Morocco.Africa produces a very small share of the world supply of diatomite (a fine siliceous earth, used as an abrasive). The most important deposit is in Kenya.Water resourcesIn general, the seasonal distribution of river flow in Africa reflects the seasonal rainfall pattern; the amount of groundwater entering the river channels during the dry season is comparatively small. Important modifications in the flow of some rivers are caused by the presence of large lakes and swamps, which act as natural storage reservoirs, by the construction of dams on their courses, and by the incidence and severity of drought.Surface waterAlthough the surface area of Africa is about one-fifth of the Earth's land surface, the combined annual flow of African rivers is only about 7 percent of the world's river flow reaching the oceans.North Africa's few perennial rivers originate in the mountains of the Maghrib, and their water is used extensively for irrigation. The large number of wadis, or ephemeral watercourses, to be found throughout the Sahara and the eastern Mediterranean coastal lands become filled with water as a result of the rare and erratic storms that occur over mountainous areas; otherwise they remain dry.From the relatively well-watered areas of western and equatorial Africa, the Sénégal, the Niger, the Logone–Chari, and the Nile rivers flow through the drier inland zones. Of these, the Niger River, originating in the Fouta Djallon region of Guinea, is retarded in the lake and swamp area south of Timbuktu in Mali, and the Logone–Chari feeds Lake Chad.The Nile (Nile River), the world's longest river, receives more than 60 percent of its water from the Ethiopian Plateau, although its source is much farther south in the mountains of Burundi. Since the completion of the Aswan High Dam, only a small proportion of the river's total flow reaching Egypt enters the Mediterranean Sea.A number of rivers flowing in a more or less southerly direction into the Atlantic Ocean drain the southern part of western Africa. Many flow rapidly over bedrock before entering the coastal plains, draining into the system of lagoons and creeks along the coast. During the dry season the upper reaches of these rivers are without water; but in Guinea, Sierra Leone, and Liberia, where the dry season is fairly short, the rivers flow throughout the year.In the well-watered western part of equatorial Africa the total average annual flow of the Congo River is enormous: some 44 trillion cubic feet. River flow at the lower end of the basin has two maxima: one that corresponds with the rainy season north of the equator, the other with the rainy season that occurs when it is summer in the Southern Hemisphere. The waters in the lower reaches of the river are slightly acid after traversing the large swamps situated in the centre of the basin.East Africa's many lakes stretch along the East African (East African lakes) Rift Valley from the Red Sea to the mouth of the Zambezi River. Evaporation from most of them exceeds their surface rainfall, and in consequence their outflow is less than the quantities brought in annually by their tributaries. They often govern river flow by acting as storage reservoirs—decreasing the flood flow and increasing the dry-season flow. A number of the rift valley lakes are situated in closed basins and contain high percentages of dissolved salts. The largest of these are Lakes Rudolf (Turkana), Natron, and Eyasi.Rainfall over much of southern Africa is small, and the majority of the rivers originating there have an intermittent flow. Some large perennial rivers (e.g., the Okavango, the Zambezi, and the Orange) flow from areas of abundant rainfall into the drier zones.The conditions under which groundwater is found and the quantity and quality of groundwater reserves are closely related to geologic structure. Large inland depressions in Africa's basement rock, having been filled with sedimentary layers of continental origin, sometimes form important groundwater reservoirs, notably those in the Taoudeni–Niger region, in the central Sahara between the Atlas and Ahaggar mountains; in the Libyan Desert; and in Chad, the Congo basin, the Karoo area of South Africa, and the Kalahari.The East African plateaus usually contain little or no quantities of groundwater, and aquifers (geologic formations containing water)—generally of local importance—are found only in humid areas where the crystalline rock is weathered or fractured.The chalky shales (rocks of laminated structure formed by the consolidation of clays) and dolomitic limestones (those containing calcium magnesium carbonate), which sporadically cover the basement rock, may contain important aquifers; those in Zambia and South Africa are major sources of water.In the Sahara a rock stratum called the Continental Intercalary series, which dates from the early Cretaceous Period and which includes the Nubian sandstones of southern Egypt, is the most important water-bearing layer. It extends over very large areas and reaches a thickness of more than 3,000 feet; in Egypt and Algeria it is a major source of artesian water. In The Sudan it sometimes lies directly on the Precambrian bedrock and contains underground water layers of local importance. Overlaying the Continental Intercalary series, but generally separated from it by a thick marine deposit, is a younger Tertiary layer called the Continental Terminal, which is the second largest aquifer in this area. Both these layers contain “fossil” water—i.e., water that entered the layers when rainfall in and around the Sahara was much more abundant than today. Near the surface, aquifers are found in such geologically recent deposits as alluvial deposits and sand dunes.In the coastal areas of Senegal, Côte d'Ivoire, Ghana, Togo, Benin, Nigeria, Cameroon, Gabon, Congo (Brazzaville), Angola, Mozambique, the East African countries, and Madagascar, aquifers are found in sandstone, limestone, and sand and gravel sediments. Intensive exploitation, however, may result in saltwater intrusions.The Jurassic limestones of the mountainous area of the Maghrib are much more abundant in water sources than are dolomitic limestones. Around the cape in South Africa, sandstones and limestones contain very little water.Yields from aquifers with good porosity, such as coastal sedimentary rocks or alluvial deposits, vary from a few cubic feet per hour in the fine-grained sands found in many parts of the continent to 35,000 cubic feet (990 cubic metres) per hour in the coarse gravels of the Nile delta. The capacity of wells in the Continental Terminal is generally somewhat lower, and those in the Continental Intercalary and the Karoo formations can also deliver moderate to high yields.In North Africa limestones containing many cracks and fissures may yield thousands of cubic feet of water per hour, while in Congo (Kinshasa), Zambia, and South Africa large yields are drawn from dolomitic limestones.The harder sandstones, sandy shale, and quartzites of Precambrian and Paleozoic age are not generally very porous, and water is obtained only from fractured or weathered deposits. West African, Angolan, and Tanzanian wells in these formations produce only a few cubic feet per hour. Crystalline and metamorphic rocks are almost impermeable except where fractured or weathered. Volcanic rock, especially the basalts, may yield up to 1,060 cubic feet per hour.Most of the exploited groundwater is generally fit for consumption because the dissolved minerals in water from shallow wells, particularly in the sandy aquifers of West Africa, are quite low. Groundwater from deeper marine layers, however—such as occurs in parts of North Africa, Mozambique, Ethiopia, and South Africa—may have a high content of dissolved salts. In moist, tropical countries water from Precambrian rocks generally contains only small amounts of dissolved minerals, whereas in the volcanic areas of East Africa groundwater may have so high a content of fluorine as to make it unfit for human consumption. There, and elsewhere in Africa, hot (possibly medicinal) springs with high mineral contents occur.Availability for human useThe pronounced seasonal character of rainfall and the fact that many rivers stop flowing during the dry season have necessitated the development of groundwater for human use, and the tapping of local aquifers has become important in many parts of the continent.Large-scale irrigation has long been practiced mainly in North Africa, Egypt, The Sudan, South Africa, Mali, Zimbabwe, and Mozambique. Medium-scale irrigation projects have been operated in Madagascar, Senegal, Somalia, and Ethiopia. In Côte d'Ivoire, Burkina Faso, Kenya, Nigeria, Ghana, and Zambia, medium- to small-scale projects have been constructed.More than 50 river and lake basins are shared by two or more countries, and the development of their resources requires the cooperation of the basin states and several intergovernmental agencies—such as the Organization for the Development of the Sénégal River, the Niger Basin Authority, and the Lake Chad Basin Commission.Several large reservoirs were built in the late 20th century, such as the Aswan High Dam, Roseires, and Khashm al-Qirbah reservoirs in the Nile basin, Kainji on the Niger, Akosombo on the Volta, Kariba on the Zambezi, Cahora Bassa on the Zambezi in Mozambique, Kossou on the Bandama in Côte d'Ivoire, Kafue on the Kafue in Zambia, and Inga I and II on the Congo River in Congo (Kinshasa). At a number of man-made lakes, research centres have been set up to study resettlement problems, the full use of ecological conditions, and the control of health hazards that sometimes occur.Biological resourcesAfrica's naturally occurring biological resources—its immensely varied vegetational cover, vast insect life, and diverse animal life—have been described above. When combined with cultivated crops and domestic animals, these resources represent the great bulk of the continent's economic wealth.Botanical resourcesThe two most economically important types of vegetation are forests (forest) and grasslands. Among the forested areas, the tropical forests contain much of the valuable timber. The vast equatorial lowland rain forest has the greatest variety of tree species, but the species most commercially in demand are found in the zones of broad-leaved woodlands and tropical highland forests. The true value of the forested areas, however, cannot be ascertained exactly, as original forests are progressively being converted to farming areas, and few governments have undertaken comprehensive land-use surveys to determine their present extent.A large proportion of the land surface of Africa bears vegetation in which grass (grassland) is an essential feature. This abundance of grass has made possible the continent's enormous and varied populations of herbivorous mammals, both wild and domesticated. The tall and fibrous invasive grasses in forest environments and in large tracts of wooded grasslands are seldom very palatable to livestock; but in those parts of the continent where good forage grows naturally or has been introduced, livestock raising is of great economic importance.The Albida acacia tree of the “farmed parkland” areas of West Africa is of special economic importance. Unlike almost all other dry woodland trees, whose leaf shedding normally occurs at the onset of the dry season, the Albida appears to have a period of partial dormancy during the rainy season and springs to life only at the beginning of the dry season. At such periods its foliage is abundant and—being a palatable leguminous species—is much prized as browse for sheep, goats, and cattle. The smaller leafy branches are frequently fed to stock. The tree flowers and produces fruits, which are harvested, dried, and fed as a protein concentrate to stock at the height of the dry season.Animal resourcesAlthough water buffalo, oxen, horses, mules, donkeys, and camels are used primarily as draft, pack, or riding animals in Africa, they also provide milk, meat, hides, or skins.The water buffalo is an offshoot of the Asiatic buffalo (Bubalus bubalis); it arrived in Africa in relatively recent times and is now found almost exclusively in Egypt. The domesticated African water buffalo is used to cultivate irrigated land (mainly in the Nile delta) and to provide milk and meat. Because of its intractability and wild nature, however, the African elephant—unlike the Asian elephant—is not used for draft or haulage purposes.Oxen (ox) are widely used in Africa for agricultural purposes, especially for plowing and cultivation; they are also trained to thresh grain, pump water, and act as pack animals. Bullock (castrated oxen) plowing is well developed in the countries of North Africa, in Ethiopia and The Sudan, and farther west in Chad, in northern Nigeria, and in the savanna climatic zone of West Africa. Plowing and cultivation by oxen is also well developed in areas of eastern and southern Africa that are free of the deadly tsetse fly. Females used for work may also be milked. Work oxen are often used for meat and to provide hides.Horses (horse) and ponies are principally found in Morocco, Algeria, Tunisia, Chad, Ethiopia, Mali, Niger, Nigeria, Senegal, Burkina Faso, Egypt, South Africa, and Lesotho. Horses are used as riding or pack animals and in a number of areas are bred with donkeys to produce mules. Few are kept in areas where tsetse flies are present. Five main types of horses inhabit Africa: the Darfur pony, the Dongola horse, the Ethiopian-Galla horse, the Somalia pony, and the South African horse (including the Basuto pony). In North Africa, types also have evolved as a result of selection and crossing with exotic Arab, Barb (Barbary), and Thoroughbred horses. Arab and Thoroughbred influence may also be noted in southern Africa.The distribution of the ass roughly corresponds to that of the horse, except that it also extends into the livestock areas of eastern and central Africa. Mules (mule) are found in Algeria, Ethiopia, Morocco, Somalia, South Africa, and Tunisia, where they provide farm draft power and are used as pack animals and for riding. The ability of mules to perform work in hot, dry climates is superior to that of most other farm animals.The Arabian camel, or dromedary, is widely dispersed in the drier regions of northern and eastern Africa. Although used principally as a pack animal, it also is used for land cultivation, water pumping, and human transportation. The camel is essentially a bush browser and, if reasonably well fed and watered, may produce about 11 to 13 pounds (5 to 6 kilograms) of milk daily, in addition to that fed to the calf. The milk is prized by the camel herders and their families. Camel meat and camel hides find a ready market among Muslim communities.Cattle provide hides, and sheep, goats, and pigs provide skins. Skins of the Maradi, Sokoto, and Kano red goats from Niger and Nigeria are greatly prized by the Morocco leather trade. In the areas north and south of the tropical zone, African sheep are covered with wool, but in the tropics they are hairy. In elevated areas, such as Ethiopia, where temperatures are modified by altitude, some sheep may be partially wooled, at least on the back and buttocks. The wooled sheep of North Africa are largely of the woolly Barbary type, which was originally introduced to Africa from the Middle East.The great herds of wild African herbivores include the principal game animals. African antelope have been important throughout human history as sources of meat and such by-products as hides and bone; and they, along with other large mammals, became prized by trophy hunters. African elephants have been sought for centuries for the ivory in their tusks, but the severe reduction of their numbers by the late 20th century has led to a total ban on hunting them in most African countries.The most economically useful fish found in the African waters include many species of freshwater fish. Important among the marine fish are flounder, halibut, sole, redfish, bass, conger, jack, mullet, herring, sardine, and anchovy. Crustaceans are important for local consumption and for export, as are oysters (for pearls), trochus shells, corals, and sponges. The most economically important aquatic mammal is the Southern, or Cape, fur seal.AgricultureAgriculture is by far the single most important economic activity in Africa. It provides employment for about two-thirds of the continent's working population and for each country contributes an average of 30 to 60 percent of gross domestic product and about 30 percent of the value of exports. Nonetheless, arable land and land under permanent crops occupy only about 6 percent of Africa's total land area.Except for countries with sizable populations of European descent—such as South Africa, Zimbabwe, and Kenya—agriculture has been largely confined to subsistence farming and has been considerably dependent on the inefficient system of shifting cultivation (shifting agriculture), in which land is temporarily cultivated with simple implements until its fertility decreases and then abandoned for a time to allow the soil to regenerate. In addition, over most of Africa arable land generally has been allocated through a complex system of communal tenure and ownership rather than through individually acquired title, and peasant farmers have had rights to use relatively small and scattered holdings. This system of land ownership has tended to keep the intensity of agricultural production low and has inhibited the rate at which capital has been mobilized for modernizing production. A number of countries have made efforts to raise productive levels by selecting better varieties of seeds and planting materials, using tractors and other mechanized equipment, or increasing the use of mineral fertilizers and insecticides. Such measures, however, have been relatively limited, and they have raised concerns about their part in accelerating soil erosion and desertification. In areas of cash-crop production, land has become private rather than community property, and cultivation is intensive.The persistence of relatively low-productivity agricultural systems over large parts of the continent also stems from a lack of integration between crop production and animal husbandry. Traditionally, sedentary cultivators like the Hausa in Nigeria and the Kikuyu in Kenya live apart from their nomadic herdsmen neighbours (the Fulani and Masai, respectively), with the result that over large areas of the continent farmers do not have access to animals for draft power or to manure for fertilizer. The incidence of such insect pests as the tsetse fly also discourages mixed farming in many areas.The need to sharply increase food production to meet the demands of a rapidly growing population, however, has remained paramount. Intense research at such centres as the International Institute of Tropical Agriculture in Ibadan, Nigeria, has been directed at developing high-performing varieties of crops and designing more appropriate cropping systems. One product of such research is a genetically improved strain of corn (maize). Corn is not in itself a balanced food, being deficient in some amino acids; but a scientific breakthrough in the mid-1960s resulted in an increase of the amino acids lysine and tryptophan in certain new varieties of corn called opaque, or high-lysine, strains. These varieties initially produced low yields, were more prone to disease and vermin, and had a soft texture that was not desirable. Breeding programs, however, have since corrected these defects, and the new strains have begun to improve the nutritional value of diets in Africa (which consist mainly of corn preparations).Principal cropsCereals and grainsAfrica produces all the principal grains—corn, wheat, and rice—in that order of importance. Corn has the widest distribution, being grown in virtually all ecological zones. Highest yields per acre are recorded in Egypt and on the Indian Ocean islands of Réunion and Mauritius, areas where production is under irrigation. Millet and sorghum are also produced but principally in the savanna regions of the continent. Rice production and consumption have become increasingly important and are closely associated with areas of rapid urbanization. The most important rice-producing countries are Egypt, Guinea, Senegal, Mali, Sierra Leone, Liberia, Côte d'Ivoire, Nigeria, Tanzania, and Madagascar. Wheat production was once restricted to South Africa, the countries of North Africa, and the highland zones of Ethiopia and Kenya, but new varieties have extended cultivation (under irrigation) to countries in the savanna region such as Nigeria.Legumes and fodderFodder crops are not widely grown except in subtropical areas of North Africa and the highland zones of East and southern Africa, where pure stands of alfalfa (lucerne) are raised. Berseem (a type of clover used for forage) is also grown in Egypt and The Sudan under irrigation. Protein-rich legumes are produced widely, usually sown together with other crops. They include velvet beans, cowpeas, soybeans, and lablab (hyacinth beans). In North Africa broad beans and vetches are also produced. Peanuts (groundnuts) are grown widely in western Africa, both for domestic consumption and for export.Tubers and root cropsCultivation of the hardy cassava has expanded tremendously, particularly in West and central Africa; it has displaced the cultivation of yams in many areas and has ceased to be regarded as just famine reserve. Potatoes are cultivated in the higher elevations of such countries as Ethiopia, Kenya, and Madagascar, as well as in areas of Mediterranean climates in North and South Africa. Sweet potatoes have a more tropical and subtropical distribution, while the plantain is grown extensively in the tropical forest zones.Fruits and vegetablesAmong the important fruits are bananas, pineapples, dates, figs, olives, and citrus; the principal vegetables include tomatoes and onions.The banana is well distributed throughout tropical Africa, but it is intensively cultivated as an irrigated enterprise in Somalia, Uganda, Tanzania, Angola, and Madagascar. Also widely cultivated is the pineapple, which is produced as a cash crop in Côte d'Ivoire, the Congo basin, Kenya, and South Africa.A typical tree of desert oases, the date palm is most frequently cultivated in Egypt, The Sudan, and the other countries of North Africa. The fig and olive are limited to North Africa, with about two-thirds of the olive production being processed into olive oil.The principal orange-growing regions are the southern coast of South Africa and the Mediterranean coast of North Africa, as well as Ghana, Swaziland, Zimbabwe, Congo (Kinshasa), and Madagascar. The largest yields are produced in countries where basin irrigation is practiced. South Africa is the largest producer of grapefruit, followed by The Sudan.Tomatoes and onions are grown widely, with the largest-producing areas bordering the Mediterranean. Large vegetables, such as cabbages and cauliflowers, are grown in the same region, from where it is possible to export some quantities to southern Europe. Important vegetables of tropical Africa include peppers, okras, eggplants, cucumbers, and watermelons.Beverage cropsTea, coffee, cocoa, and grapes are all grown in Africa. Kenya, Tanzania, Malaŵi, Zimbabwe, and Mozambique are the largest producers of tea, while Ethiopia, Uganda, Côte d'Ivoire, Kenya, Cameroon, Congo, Tanzania, and Madagascar are the major producers of coffee. Cocoa is essentially a tropical forest crop. Its cultivation is concentrated in West Africa, with the principal producers being Côte d'Ivoire, Ghana, Nigeria, and Cameroon. All of these crops are largely grown for export. Sharp price fluctuations have caused African countries to form international cartels with other producing countries in an effort to regulate the market and negotiate better prices. Grapes are produced in northern Africa and in South Africa, essentially for the making of wine for European markets. The agricultural policy within the European Community (EC), however, has had a restraining effect on the scope of production.FibresLarge areas of Africa raise cotton for textile manufacture. The principal producing countries are Egypt, The Sudan (especially the Al-Jazīrah Plain), Zimbabwe, and Mali. Sisal production is also important, especially in the eastern African countries of Tanzania, Kenya, and Madagascar, as well as in Angola and South Africa. Some countries, notably Nigeria, promote the cultivation of kenaf (one of the bast fibres).Other cash cropsThe oil palm, producing palm oil and palm kernels, grows widely in secondary bush in the tropical forest zones. There are large plantations in Nigeria, Côte d'Ivoire, and Congo. Coconuts are important in the Comoros, Ghana, Côte d'Ivoire, Mozambique, Nigeria, and Tanzania. Kola nuts are grown principally in the forested regions of Nigeria, Ghana, Côte d'Ivoire, Sierra Leone, and Liberia. The cashew tree is grown to a limited extent in East Africa and to a lesser extent in the coastal countries of West Africa. Rubber is produced principally in Nigeria and Liberia. Tobacco is widely cultivated as an export crop in Zimbabwe, Malaŵi, Tanzania, Nigeria, and South Africa. Sugarcane is also widely grown but largely for domestic consumption. Major producers include South Africa, Egypt, Mauritius, and The Sudan.Livestock and fishingCattle, sheep, and goats form the bulk of livestock raised. Except in South Africa, most of these animals are raised essentially for beef. Sheep in the north and south are also kept for their wool; South Africa alone produces half of the entire continental production, much of the clip from merino or crossbred merino sheep. In the tropical areas, however, other livestock products include hides and skins. It is estimated that the annual output of hides is in the range of 10 percent of the total population of cattle, while that of sheepskins and goatskins is approximately 25 percent. The number of game hides and skins processed and sold annually is not accurately known. Except in South Africa, Zimbabwe, and Kenya, production of milk and milk products is grossly insufficient to meet domestic needs. Poultry production, however, has increased tremendously, and everywhere stocks have nearly doubled since the 1960s. Nigeria, Ethiopia, Morocco, South Africa, and The Sudan are the countries with the largest poultry stocks.Fishing is important on the local level in all countries bordering the sea or inland bodies of water. Commercial ocean fishing is practiced most widely by the countries near the rich fishing grounds of the west coast—South Africa, Namibia, Angola, Nigeria, Ghana, Senegal, and Morocco. Herring, sardines, and anchovies contribute most to the ocean catch, followed by jack, mullets, sauries, redfish, bass, and conger in tropical waters and cod, hake, haddock, tuna, bonitas, and bullfish in northern and southern waters. Inland countries with well-developed fisheries include Malaŵi, Uganda, Chad, Côte d'Ivoire, and Mali; tilapia and other cichlids constitute the largest catch in inland waters. Some countries, such as Nigeria, have developed both marine and freshwater fishing industries. A number of commissions have been established to monitor and control fishery development on the continent.IndustryThe countries of North Africa, unlike those of the rest of the continent, have wide-ranging and ancient traditions of manufacture (manufacturing). At the end of the 19th century, however, Africa as a whole was regarded solely as a potential source of raw materials or as a natural market for Europe. In the course of time, limited industrialization tended to converge around the relatively large expatriate settlements, where technical considerations operated in favour of the industrialization of some areas and transport costs constituted the dominant development factor in others. Though World War II led to acceleration in the process of industrial development, by 1950 the total factory output of manufacturing industries (excluding South Africa) still remained small.After 1950 output rapidly increased. The substantial increase and its range were attributable to such factors as increased demand, the substitution of home-produced for imported goods, the encouragement of manufacturing by individual African administrations, and an influx of development capital and petrodollars. Major weaknesses nevertheless were evident, among them high capital costs, the political division of Africa into more than 50 countries, which inhibited mass production and mass marketing, and a scarcity of skilled personnel.Despite its expansion since about 1950, the relative significance of manufacturing remains considerably smaller than in the more-advanced countries and smaller also than in continental Asia and in Latin America. Furthermore, the share of manufacturing in the gross domestic product varies widely in different African countries. At the lower end of the spectrum are countries such as Equatorial Guinea, Guinea, Congo (Kinshasa), and Niger; at the upper end of the spectrum are countries such as Egypt, Algeria, South Africa, and Zimbabwe. The total output of manufacturing in South Africa alone, however, is nearly 50 percent of the output in the remainder of the continent.Manufacturing in Africa tends to concentrate on comparatively simple items and on those where some special advantage is available to the African producer, although the range of products has widened. Industrial production includes electric motors, transport equipment, and tractors, while airplanes are also assembled. The leading heavy industries are chemical and petroleum, coal, rubber, and metal manufacture. Most industrial plants, however, are of the relatively simple kind, being engaged in food processing or in manufacturing textiles, leather products, and cement or other building materials.The mining industry is an increasingly significant source of national income, foreign exchange, and raw materials for the development of local processing industries. The industry is very unevenly distributed: more than half of mineral earnings came from North Africa alone, and nearly one-fourth from southern Africa.Except in South Africa, iron and steel are used mostly for construction rather than for engineering. There are integrated iron and steel plants in Algeria, Tunisia, Egypt, Zimbabwe, and South Africa, while smaller production facilities—often based on the transformation of scrap—exist in several other countries.Petroleum-refining (petroleum) capacity is based on domestic crude-oil output in a few cases and on imported crude oil in others. In some countries the development of the petrochemical industry followed the establishment of refineries. In 1965 there were only three major petrochemical complexes in Africa—in Zimbabwe, Egypt, and South Africa; by the late 20th century several more countries had large refinery capacities, including Algeria, Ghana, Kenya, Libya, Morocco, Nigeria, Senegal, The Sudan, and Tunisia.Most of the textiles (textile) are processed in bleaching, dyeing, and printing establishments that form an integral part of composite spinning and weaving units. With the exception of Egypt, producers have concentrated on the home market and on the manufacture of cotton textiles. Although African countries export textiles, their imports are usually larger. Rayon–synthetic and woolen materials are, for the most part, imported. Ready-made clothing, both domestic and imported, has emerged as a major market factor.Most African countries have cement plants, the leading producers being South Africa and Algeria. The transport costs of cement make its price variable. Prices are lowest on the North African coast, somewhat higher on the west and east coasts, and highest in the inland countries.By far most of Africa's wood output is used for fuel. Sawmills, however, are distributed throughout the continent. Plants for the manufacture of plywood, particleboard, and fibreboard have a considerable amount of excess capacity. The pulp and paper industry is concentrated in North Africa and in southern Africa, although a number of small paper mills have been established in other parts of the continent. The main products of the paper industry proper comprise newsprint, printing and writing papers, paper and paperboard, and industrial paper. The bulk of the output of all paper products is directed to national markets.PowerA spectacular development in the use of electric energy has taken place in the second half of the 20th century, partly because of the growth of the petroleum industry and partly because of the establishment of large hydroelectric (hydroelectric power) plants and some thermoelectric plants. The increased quantity and quality of electric energy have given rise to problems of transmission and distribution. Unlike thermoelectric plants, which may be sited where the consumer demand is greatest, sites of hydroelectric installations are not flexible, and the type of transmission lines in use has therefore changed. Although in the 1950s it was common practice to use lines with transmission voltages of less than 220 kilovolts, transmission lines were later built that could handle higher voltages. In Nigeria, for example, 330-kilovolt lines were strung; similar lines were used in Zimbabwe's system, which feeds Harare and Bulawayo in Zimbabwe, as well as the Copperbelt in Zambia. This same system is interconnected in the north with the large Katanga (Shaba) region hydroelectric power stations in Congo (Kinshasa). The construction of high-tension lines to supply power to the Katanga Copperbelt was completed in 1982. Much of the power for Egypt's population centres is supplied by lines from such hydroelectric power stations as that at the Aswan High Dam. Construction of 533-kilovolt lines to transmit power from the Cahora Bassa hydroelectric station in Mozambique to South Africa was completed in 1974. The possibility of supplying landlocked states with energy from the large hydroelectric plants in the coastal states is more likely to be considered in the future.A number of steam power stations are located in ports and cities near the coasts. The largest installations of this kind operate in Tunis, Tun.; Casablanca and Oujda, Mor.; Dakar, Senegal; Abidjan, Côte d'Ivoire; and Lagos, Nigeria. Steam power stations using coal are by far the most common, especially in South Africa.Electric-energy consumption in large urban centres, especially when they are near coastal towns and mining areas where industrial activity has taken shape, has increased considerably. Although some countries have extended networks to the rural areas or have increased the numbers of isolated, low-powered stations and independent networks, progress in rural electrification has not been especially noteworthy.TradeInternal tradeIntra-African trade records frequently understate the amount of trade—partly because of the lack of adequate statistics and partly because of the high rate of smuggling, which allows a substantial amount of traditional border trade to continue unrecorded. Apart from this, commerce between African states has been handicapped by a tendency for trade to remain concentrated within the common-currency areas and trade zones that developed among African countries during the colonial era, by the often inadequate means of transport and communication, by the lack of complementary agricultural or other products, and by the limited development of manufacturing industries.Much of the intra-African trade consists of consumables—food, drinks, tobacco, sugar, cattle, and meat. The growth of industrialization in some countries, however, has been accompanied by an increase in the trade of durable and nondurable manufactured goods. There has also been a large amount of reexport trade between the coastal and inland states, especially in machinery, transport equipment, and spare parts.Common-currency and trade zones that have evolved through the granting of preferences or the operation of common currencies inherited from former colonial powers include: the Customs and Economic Union of Central Africa (UDEAC), comprising Cameroon, Gabon, the Central African Republic, Equatorial Guinea, and the Congo, which has become part of the larger Economic Community of Central African States (CEEAC) that also includes Angola, Burundi, Chad, Congo (Kinshasa), Rwanda, and São Tomé and Príncipe; the Economic Community of West African States (ECOWAS), consisting of Benin, Burkina Faso, Cape Verde, Côte d'Ivoire, The Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Niger, Nigeria, Senegal, Sierra Leone, and Togo; the Southern African Development Community (SADC), comprising Angola, Botswana, Congo (Kinshasa), Lesotho, Madagascar, Malaŵi, Mauritius, Mozambique, Namibia, Seychelles, South Africa, Swaziland, Tanzania, Zambia, and Zimbabwe; and the Arab Maghreb Union (UMA), grouping Algeria, Libya, Mauritania, Morocco, and Tunisia.External tradeSince the outbreak of World War II there has been a considerable expansion in Africa's overall external trade. The growth compares favourably with that of the other developing regions, such as Latin America; the value of imports, however, has outweighed exports for some time, resulting in huge trade imbalances for most African countries. The large expansion in African exports is generally attributed to the increase in the demand for primary commodities during World War II and in the immediate postwar reconstruction period. Subsequently, the attainment of independence by a large number of African countries—especially in the early 1960s—followed by a bid for economic development, strengthened the export-expansion drive. Another reason for the rapid growth in African exports was the temporary increase in the price of primary commodities, although subsequently the general trend, except for petroleum, has been toward depressed commodity prices. The persistence of this situation has been part of the reason the economies of many African countries have become crippled by huge foreign debts.ExportsAn important factor that has influenced the growth of African exports was the discovery of petroleum in several countries, notably Libya, Algeria, Nigeria, Gabon, Angola, Congo (Brazzaville), and Cameroon, and the dramatic price increases brought about by the Organization of Petroleum Exporting Countries (OPEC) in the 1970s. Other factors include the discovery and the increased exploitation of minerals that are in high demand, such as diamonds—especially in Sierra Leone, Congo (Brazzaville), the Central African Republic, and Congo (Kinshasa)—and the exploitation of other minerals, such as uranium ore.Since achieving independence, many African countries have made attempts to diversify external trade relations. The record of achievement has been poor, however, because Africa's trade patterns have continued to reflect the influence of traditional links with the countries of western Europe. These links have been further consolidated through a series of agreements, collectively called the Lomé Conventions, that have guaranteed preferential access to the European Economic Community (European Community) (EEC) for various export commodities from African states and that have provided European aid and investment funding. Nonetheless, a significant export trade has developed with the United States and Japan.In most African states one or two primary commodities dominate the export trade—e.g., petroleum and petroleum products in Libya, Nigeria, Algeria, Egypt, Gabon, Congo (Brazzaville), and Angola; iron ore in Mauritania and Liberia; copper in Zambia and Congo (Kinshasa); cotton in Chad; coffee in Burundi, Uganda, Rwanda, Ethiopia, Madagascar, Kenya, and Côte d'Ivoire; and sugar in Mauritius.ImportsThe tremendous increase of Africa's import trade has meant that the import bill of most African states has exceeded their export earnings; in consequence, many governments have established import restrictions or subsidized many of the required imports. The bulk of imports comes from western Europe, especially the EEC countries, with strong trade ties persisting along former colonial lines. There has, however, been a substantial increase in imports from the United States, Japan, and South Africa. Imports are needed primarily to develop manufacturing industries and are, therefore, confined for the most part to mineral fuels, industrial goods, machinery, transport equipment, and durable consumer goods.TransportationAlthough there were highly developed transport networks in many parts of Africa in precolonial times, during the colonial era that followed, these networks were restructured to penetrate into the interior from the seaports and, in the main, to serve the commercial and administrative needs of the colonial powers. Their fragmentation, which led to interregional links being but thinly developed, resulted from the juxtaposition of varied and difficult terrains, the economic artificiality of certain national frontiers, the lack of a developed intra-African trade, and the strong orientation of commodity trade with the administering countries. All of this was further complicated by the existence of vast unpopulated areas lying between the main centres.The emergence in the 1960s of independent African governments who recognized the need to lift economies from their generally very low levels and, above all, to develop agriculture and embark on industrialization heralded improvements in economic planning, the development of transport networks, and the introduction of cheaper freight rates. But there remained a serious shortage of qualified African labour to plan and manage transport systems at the national or multinational level and, simultaneously, to keep up with the rapid development of transport technology outside Africa.Animal transportThere is some evidence that before the arrival of the camel, which was introduced into Africa via Egypt at the time of the Arab conquest, bullocks were used either as pack animals or to draw carts from the northern countries across the Sahara to the gold-producing areas of the ancient Sudan. From the 16th century onward, the Portuguese developed transport inland from the coast at Mozambique, and, from the 17th century, first the Dutch and then British settlers from the Cape trekked northward and northeastward with their wagons. Except in such highland areas as Ethiopia, where pack animals were and still are used, the tsetse fly often prevented the use of animal transport. With the steady progress in the development of transport infrastructure in many African countries, the use of bullocks in southern Africa, donkeys in North and western Africa, horses in northern Nigeria, and camels in western and North Africa and the Horn of Africa has been reduced, but the extent of this reduction cannot be accurately gauged.Motor transportThe arrival and rapid development of the internal-combustion engine in the 1920s transformed the collection and distribution of goods and personal travel. Roads were built, particularly in North and southern Africa, but also in parts of the west and east. World Bank loans since the 1950s, supplementing contributions to road and highway development from national budgets, have financed the building and improvement of road networks in many African countries.Rail transportThe early railways were constructed partly to facilitate the administration of interior regions and to bring supplies from ports to central consumption or distribution points and partly—especially in the south—to enable valuable minerals or commodities to reach the coast for export. In Africa, as in Europe and North America, the major period of railway development extended from the end of the 19th century to the end of World War I. This expansion, however, was not coordinated: railways with different gauges of track were built and were operated with rolling stock of different braking and coupling systems. Thus, the colonizing powers left a difficult and costly legacy for independent African countries who wished to link themselves together. As with roads, rail networks have been improved considerably since the 1960s and, as a result, there has been a lowering of transport costs.Air transportAir transport is well suited to Africa's geographic vastness, and it has become the primary means of international and sometimes of national travel in Africa. During the late 1940s and the '50s, as great advances were made in the extension and improvement of rail and road services, a new transport factor emerged in the introduction of internal and international scheduled air services. The rapid development of air transport increased the movement of goods and people and began to open up the hitherto largely closed interior of the continent. Transport became much quicker and usually cheaper. Since then, internal air services have steadily increased, and intercontinental air transport, especially of passengers, has developed greatly. The largest international airports are at Casablanca, Mor.; Las Palmas, Canary Islands; Cairo; Dakar, Senegal; Abidjan, Côte d'Ivoire; Lagos, Nigeria; Douala, Cameroon; Addis Ababa, Eth.; Nairobi, Kenya; and Johannesburg, S.Af.Historically, throughout the vast interior between the Sahara and the Zambezi River, people or goods were transported by canoe or boat on the great river systems of the Nile, Sénégal, Niger, Congo, Ubangi, and Zambezi rivers and on the few but very large lakes. Where conditions allowed, engine-powered craft later supplemented or displaced canoes, but further development of water transport has been slight. Also notable were the construction of lake ports and the installation of rail ferries across Lake Victoria.Meanwhile, on the coasts, artificial harbours have been developed. New berths have been added to established port facilities, and a number of ports have been constructed. In planning new ports, the choice of site, probable costs, and the possibilities of using containers or other unitized loads have been taken into consideration.Robert K.A. Gardiner Akinlawon Ladipo MabogunjeAdditional ReadingGeneral worksOverviews of the continent may be found in R. Mansell Prothero (ed.), A Geography of Africa, rev. ed. (1973); John I. Clarke (ed.), An Advanced Geography of Africa (1975); William A. Hance, The Geography of Modern Africa, 2nd ed. (1975); Alan C.G. Best and Harm J. De Blij, African Survey (1977); R.J. Harrison Church et al., Africa and the Islands, 4th ed. (1977); A.T. Grove, Africa, 3rd ed. (1978), and The Changing Geography of Africa (1989); J.M. Pritchard, Africa, rev. 3rd ed. (1979, reissued 1986); Phyllis M. Martin and Patrick O'Meara (eds.), Africa, 2nd ed. (1986); Paul Bohannan and Philip Curtin, Africa and the Africans, 3rd ed. (1988); and Alan B. Mountjoy and David Hilling, Africa: Geography and Development (1988). Roland Oliver and Michael Crowder (eds.), The Cambridge Encyclopedia of Africa (1981), is also useful. Regine Van Chi-Bonnardel, The Atlas of Africa (1973), presents general physical and thematic maps, as well as maps and text for each country. Jocelyn Murray (ed.), Cultural Atlas of Africa (1981), includes maps and text on Africa's physical geography, culture, history, language, and social life. General treatments of European exploration in Africa are contained in Heinrich Schiffers, The Quest for Africa: Two Thousand Years of Exploration (1957; originally published in German, 1954); and Robert I. Rotberg (ed.), Africa and Its Explorers: Motives, Methods, and Impact (1970). Useful annuals that contain historical overviews of each African country and updated essays on the continent's political, social, and economic developments include The Middle East and North Africa; Africa South of the Sahara; and Africa Contemporary Record. Davidson S.H.W. Nicol Ed.Geologic historyGeneral discussions of African geology may be found in L. Cahen and N.J. Snelling, The Geochronology and Evolution of Africa (1984); and Adetoye Faniran, African Landforms (1986). Books and essays on specific aspects include Bernard Bessoles, Géologie de l'Afrique: le craton Ouest Africain (1977); Russell Black, “Precambrian of West Africa,” Episodes, 4:3–8 (1980); M. Deynoux, J. Sougy, and R. Trompette, “Lower Palaeozoic Rocks of West Africa and the Western Part of Central Africa,” in C.H. Holland (ed.), Lower Palaeozoic of North-western and West-central Africa (1985), pp. 337–495; A. Kröner, “The Precambrian Geotectonic Evolution of Africa: Plate Accretion Versus Plate Destruction,” Precambrian Research, 4(2):163–213; A. Kröner et al., “Pan-African Crustal Evolution in the Nubian Segment of Northeast Africa,” in A. Kröner (ed.), Proterozoic Lithospheric Evolution (1987), pp. 235–257; A.J. Tankard et al., Crustal Evolution of Southern Africa: 3.8 Billion Years of Earth History (1982); J.R. Vail, “Outline of the Geochronology and Tectonic Units of the Basement Complex of Northeast Africa,” Proceedings of the Royal Society of London, Series A, 350(1660):127–141 (1976); and J.B. Wright (ed.), Geology and Mineral Resources of West Africa (1985).Alfred KrönerThe landDescriptions of Africa's physical geography can be found in the general works listed above and in M.F. Thomas and G.W. Whittington (eds.), Environment and Land Use in Africa (1969). William G. McGinnies, Bram J. Goldman, and Patricia Paylore (eds.), Deserts of the World (1968), includes detailed appraisals of research on the physiography, hydrology, soils, weather and climate, vegetation, and fauna of the Kalahari, Namib, and Sahara. A comprehensive account of the geomorphology of Africa is given in Lester C. King, The Morphology of the Earth, 2nd ed. (1967), pp. 241–309. Regional geographies include Jean Despois and René Raynal, Géographie de l'Afrique du nord-ouest (1967, reissued 1975); R.J. Harrison Church, West Africa: A Study of the Environment and of Man's Use of It, 8th ed. (1980); Reuben K. Udo, A Comprehensive Geography of West Africa (1978), and The Human Geography of Tropical Africa (1982); Jacques Denis, Pierre Vennetier, and Jules Wilmet, L'Afrique centrale et orientale (1971); John H. Wellington, Southern Africa, 2 vol. (1955); and A.J. Christopher, Southern Africa (1976).Robert Walter Steel H.L. Shantz and C.F. Marbut, The Vegetation and Soils of Africa (1923, reprinted 1971), was the first systematic account of major soil groups. Far more modern and useful is the basic text by Zinaida Iu. Shokalskaia, Pochvenno geograficheskiĭ ocherk Afriki (1948), also available in a German translation, Die Böden Afrikas (1953). R.P. Moss (ed.), The Soil Resources of Tropical Africa (1968); and Peter M. Ahn, West African Soils (1970), present discussions of the framework within which tropical soils may be described. B.W. Thompson, The Climate of Africa (1965), and Africa: The Climatic Background (1975), provide general information. Glenn T. Trewartha, The Earth's Problem Climates, 2nd ed. (1981), gives a more advanced account of the major climatic anomalies in Africa.Kwamina Busumafi Dickson The undoubted leading survey of African vegetation is F. White, Vegetation of Africa (1983), written to explain an accompanying map. The best comprehensive presentation of grasses remains J.M. Rattray, The Grass Cover of Africa (1960), also with a map. P.W. Richards, The Tropical Rain Forest: An Ecological Study (1952, reissued 1979), is a comprehensive classic, with a relevance well beyond its title. Brian Hopkins, Forest and Savanna (1965), is a detailed treatment of interactions in western Africa, including the effects of agriculture and pastoralism. Monica M. Cole, “The Savannas of Africa,” part III in her The Savannas: Biogeography and Geobotany (1986), pp. 111–290, is also useful. H.L. Shantz and B.L. Turner, Photographic Documentation of Vegetational Changes in Africa Over a Third of a Century (1958), presents telling site-by-site comparisons made by two doyens of science in Africa.Good general treatments of African animal life are to be found in J.L. Cloudsley-Thompson, The Zoology of Tropical Africa (1969); D.F. Owen, Animal Ecology in Tropical Africa, 2nd ed. (1976); M.J. Delany and D.C.D. Happold, Ecology of African Mammals (1979); and Jonathan Kingdon, Island Africa: The Evolution of Africa's Rare Animals and Plants (1989). Two general nature histories, approaching fauna from somewhat different standpoints although complementary to one another, are Leslie Brown, Africa: A Natural History (1965); and Archie Carr et al., The Land and Wildlife of Africa, rev. ed. (1980), a Time-Life book. Books that provide authoritative surveys of the different forms of animal life include Jonathan Kingdon, East African Mammals: An Atlas of Evolution in Africa (1971– ), splendidly artistic and alive in treatment; Walter Leuthold, African Ungulates: A Comparative Review of Their Ethology and Behavioral Ecology (1977), discussing hoofed mammals; R.E. Moreau, The Bird Faunas of Africa and Its Islands (1966); C.W. Mackworth-Praed and C.H.B. Grant, Birds of Eastern and North Eastern Africa, 2 vol., 2nd ed. (1957–60, reprinted 1980), Birds of the Southern Third of Africa, 2 vol. (1962–63, reprinted 1981), and Birds of West Central and Western Africa, 2 vol. (1970–73, reprinted 1981); Geoffrey Fryer and T.D. Iles, The Cichlid Fishes of the Great Lakes of Africa: Their Biology and Evolution (1972); Michael Holden and William Reed, West African Freshwater Fish (1972); R.A. Jubb, Freshwater Fishes of Southern Africa (1967); Vivian F.M. Fitzsimons, Snakes of Southern Africa (1962); and S.H. Skaife, African Insect Life, new ed. rev. by John Ledger (1979). John Ford, The Role of Trypanosomiases in African Ecology (1971), studies the problems caused by the tsetse fly; and Jeffrey C. Stone (ed.), The Exploitation of Animals in Africa (1988), contains several colloquium papers on wildlife, domesticated stock, and conservation.David N. McMaster Ed.The peopleGeorge Murdock, Africa: Its Peoples and Their Culture History (1959), is a standard text on the diverse peoples of Africa. Simon Ottenberg and Phoebe Ottenberg (eds.), Cultures and Societies of Africa (1960); and James L. Gibbs (ed.), Peoples of Africa (1965, reissued 1988), contain essays and readings about African peoples. John Middleton (ed.), Black Africa (1970), presents readings about the diversity of peoples and cultural change in sub-Saharan Africa. P.C. Lloyd, Africa in Social Change (1967), studies social interaction in West Africa between traditional African institutions and those imported from Europe. Ali A. Mazrui, The African Condition (1980), contains a political diagnosis; and Morag Bell, Contemporary Africa: Development, Culture, and the State (1986), examines the links between the political and economic structures and Africa's cultural variety. Joseph H. Greenberg, The Languages of Africa, 2nd ed. (1966), is a basic study of language classification; and Edgar A. Gregersen, Language in Africa: An Introductory Survey (1977), is also helpful. John S. Mbiti, Introduction to African Religion (1975), provides a summary; and Geoffrey Parrinder, Africa's Three Religions, 2nd ed. (1976), discusses Christianity, Islām, and traditional religion. On Islām in particular, René A. Bravman, African Islam (1983); and J. Spencer Trimingham, The Influence of Islam Upon Africa, 2nd ed. (1980), are general introductions.Etienne van de Walle, Patrick O. Ohadike, and Mpembele D. Sala-Diakanda (eds.), The State of African Demography (1988), reviews the state and dynamics of African populations in the late 1980s. John I. Clarke and Leszek A. Kosiński (eds.), Redistribution of Population in Africa (1982), provides overviews of population redistribution as well as national case studies and studies of the impact of settlement schemes and redistribution policies; and John I. Clarke, Mustafa Khogali, and Leszek A. Kosiński (eds.), Population and Development Projects in Africa (1985), examines the general and specific impacts of development projects upon population redistribution, with particular emphasis on The Sudan. Robert F. Gorman, Coping With Africa's Refugee Burden (1987), attempts to find solutions to the major problems of refugees in Africa since the mid-20th century. William A. Hance, Population, Migration, and Urbanization in Africa (1970), contains a major overview of population and urbanization trends. Population Growth and Policies in Sub-Saharan Africa (1986), is a study by the World Bank of the fastest-growing population region in the world.A.T. Grove and F.M.G. Klein, Rural Africa (1979), studies the rural environments in which most Africans live; and Kenneth Swindell and David J. Siddle, Rural Change and Development in Tropical Africa (1990), looks at the nature of rural change and the problems of African rural development. Josef Gugler and William G. Flanagan, Urbanization and Social Change in West Africa (1978), analyzes the process of increasing urbanization in West Africa and the related social changes; and Margaret Peil and Pius O. Sada, African Urban Society (1984), views changing urban society in West Africa. Anthony O'Connor, The African City (1983), examines the forms, functions, and patterns of growth of African cities, especially in the postindependence period; as does Richard E. Stren and Rodney R. White, African Cities in Crisis: Managing Rapid Urban Growth (1989).John Innes ClarkeThe economyThe general economic situation is explored in P. Robson and D.A. Lury (eds.), The Economies of Africa (1969); Michael Hodd, African Economic Handbook (1986); Melville J. Herskovitz and Mitchell Harwitz (eds.), Economic Transition in Africa (1964); A.M. O'Connor, The Geography of Tropical African Development, 2nd ed. (1978); Andrew M. Kamarck, The Economics of African Development, rev. ed. (1971); Ralph A. Austen, African Economic History: Internal Development and External Dependency (1987); Wilfrid Knapp, North West Africa: A Political and Economic Survey (1977); D. Hobart Houghton, The South African Economy, 4th ed. (1976); and O. Aboyade, Issues in the Development of Tropical Africa (1976). The problems of regional economic integration are treated by Adebayo Adedeji and Timothy M. Shaw, Economic Crisis in Africa (1985); Carol Lancaster and John Williamson (eds.), African Debt and Financing (1986); Arthur Hazlewood (ed.), African Integration and Disintegration: Case Studies in Economic and Political Union (1967); and B.W.T. Mutharika, Toward Multinational Economic Cooperation in Africa (1972). Useful books on mineral resources and industrialization include Oye Ogunbadejo, The International Politics of Africa's Strategic Minerals (1985); and A.F. Ewing, Industry in Africa (1968). Natural resources and environmental problems are covered by Neville Rubin and William M. Warren (eds.), Dams in Africa: An Inter-disciplinary Study of Man-made Lakes in Africa (1968); D.F. Owen, Man in Tropical Africa: The Environmental Predicament (1973); David Dalby, R.J. Harrison Church, and Fatima Bezzaz (eds.), Drought in Africa 2, rev. and expanded ed. (1977); and Bonaya Adhi Godana, Africa's Shared Water Resources: Legal and Institutional Aspects of the Nile, Niger, and Senegal River Systems (1985). Agricultural development and the agrarian crisis are presented by William Allan, The African Husbandman (1965, reprinted 1977); Prabhu Pingali, Yves Bigot, and Hans Binswanger, Agricultural Mechanization and the Evolution of Farming Systems in Sub-Saharan Africa (1987); John W. Mellor, Christopher L. Delgado, and Malcolm J. Blackie (eds.), Accelerating Food Production in Sub-Saharan Africa (1987); Paul Harrison, The Greening of Africa: Breaking Through in the Battle for Land and Food (1987); Stephen K. Commins, Michael F. Lofchie, and Rhys Payne (eds.), Africa's Agrarian Crisis: The Roots of Famine (1986); and Robert H. Bates and Michael F. Lofchie (eds.), Agricultural Development in Africa: Issues of Public Policy (1980).Akinlawon Ladipo Mabogunje▪ Roman territory, North Africain ancient Roman history, the first North African territory of Rome, at times roughly corresponding to modern Tunisia. It was acquired in 146 BC after the destruction of Carthage at the end of the Third Punic War.Initially, the province comprised the territory that had been subject to Carthage in 149 BC; this was an area of about 5,000 square miles (13,000 square km), divided from the kingdom of Numidia in the west by a ditch and embankment running southeast from Thabraca (modern Ṭabarqah) to Thaenae (modern Thīnah). About 100 BC the province's boundary was extended farther westward, almost as far as the present Algerian-Tunisian border.The province grew in importance during the 1st century BC, when Julius Caesar and, later, the emperor Augustus founded a total of 19 colonies in it. Most notable among these was the new Carthage, which the Romans called Colonia Julia Carthago; it rapidly became the second city in the Western Roman Empire. Augustus extended Africa's borders southward as far as the Sahara and eastward to include Arae Philaenorum, at the southernmost point of the Gulf of Sidra. In the west he combined the old province of Africa Vetus (“Old Africa”) with what Caesar had designated as Africa Nova (“New Africa”)—the old kingdoms of Numidia and Mauretania—so that the province's western boundary was the Ampsaga (modern Rhumel) River in modern northeastern Algeria. The province generally retained those dimensions until the late 2nd century AD, when a new province of Numidia, created in the western end of Africa, was formally constituted under the emperor Septimius Severus. A century later Diocletian, in his reorganization of the empire, formed two provinces, Byzacena and Tripolitania, from the southern and eastern parts of the old province.The original territory annexed by Rome was populated by indigenous Libyans who lived in small villages and had a relatively simple culture. In 122 BC, however, an abortive attempt by Gaius Sempronius Gracchus to colonize Africa aroused the interest of Roman farmers and investors. In the 1st century BC Roman colonization, coupled with Augustus' successful quieting of hostile nomadic movements in the area, created conditions that led to four centuries of prosperity. Between the 1st and 3rd century AD, private estates of considerable size appeared, many public buildings were erected, and an export industry in cereals, olives, fruit, and hides flourished. Substantial elements of the urban Libyan population became Romanized, and many communities received Roman citizenship long before it was extended to the whole empire (AD 212). Africans increasingly entered the imperial administration, and the area even produced an emperor, Septimius Severus (reigned AD 193–211). The province also claimed an important Christian church, which had more than 100 bishops by AD 256 and produced such luminaries as the Church Fathers Tertullian, Cyprian, and St. Augustine of Hippo. The numerous and magnificent Roman ruins at various sites in Tunisia and Libya bear witness to the region's prosperity under Roman rule.By the end of the 4th century, however, city life had decayed. The Germanic Vandals (Vandal) under Gaiseric reached the province in 430 and soon made Carthage their capital. Roman civilization in Africa entered a state of irreversible decline, despite the numerical inferiority of the Vandals and their subsequent destruction by the Byzantine general Belisarius in 533. When Arab invaders took Carthage in 697, the Roman province of Africa offered little resistance.
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