VEGETATION AND ANIMAL LIFE OF AFRICA

Vegetation

African vegetation zones are closely linked to climatic zones, with the same zones occurring both north and south of the equator in broadly similar patterns. As with climatic zones, differences in the amount and seasonal distribution of precipitation constitute the most important influence on the development of vegetation. Moving across the continent into drier and drier climates, the typical sequence of vegetation is from tropical moist forest to moist savanna, dry savanna, semidesert, and finally desert.

Tropical Moist Forest

Tropical moist forest occurs in humid tropical areas, usually with 1,500 mm (60 in) or more of precipitation and a dry season (or seasons) of three to four months or less. West of the highlands of East Africa and centered in the basin of the Congo River is a great tropical moist forest extending some 600 km (400 mi) north of the equator and a similar distance south of the equator. On the west, the forest extends to the Atlantic coast in the Congo, Gabon, and Cameroon, and stretches in an interrupted belt along the West African coast to Sierra Leone. Tropical moist forest also occurs along the eastern side of Madagascar.

Scientists recognize two major subtypes of tropical forest: tropical rain forest and tropical wetland forest. Tropical rain forests are characterized by a dense mass of evergreens, oil palms, and numerous species of tropical hardwood trees divided vertically into strata, or layers. The upper canopy of treetops forms a dense cover over the middle layer of treetops and the surface layer of shrubs, ferns, and mosses below. Rising above the canopy are scattered tall trees, known as emergents. In dense forest environments, the shrub layer tends to be quite sparse, except along streams, because the canopy limits the amount of light that penetrates to the forest floor. Tropical rain forests are extremely diverse in species; pure stands of a single tree species are rare.

Tropical wetland forests include both freshwater and saltwater subtypes. Freshwater swamp forests cover large parts of the Middle Congo River Basin. Saltwater swamp forests occur in many areas between Senegal and Angola on the Atlantic coast and between South Africa and the Red Sea on the coast of East Africa. Mangrove species, with their characteristic tall, arched roots, are highly adapted to the fluctuating water levels and brackish water found in estuaries and other tidal environments. Mangrove forests are tangles of roots, tree trunks, and branches reaching 8 to 23 m (25 to 75 ft) high. Significant areas of mangrove forest have been lost in order to clear land for rice cultivation, particularly in West Africa.

Tropical Savanna

Surrounding the central tropical forest zone on the north, east, and south is a zone of tropical savanna vegetation that covers up to 65 percent of the continent. The savannas have somewhat drier climates compared to the tropical forests. They typically receive 500 to 1,500 mm (20 to 60 in) of precipitation per year, and have a pronounced dry season, usually from three to eight months long. Moving poleward, savanna vegetation transitions from moist woodland savanna to dry woodland savanna.

Moist woodland savanna occurs close to the tropical forest, where climates are wetter and the dry season is only three to four months. The characteristic vegetation is a mixture of tall grasses and closely spaced trees. Vegetation is especially dense along river courses, with trees lining the banks in gallery forests. Shrubs and grasses are also dense in areas where intensive cultivation and past use of fire to clear vegetation have led to the degradation of once forested lands. Shea trees occur widely; their tough outer bark is fire-resistant and their kernels are a source of oil for cooking and other uses.

Dry woodland savanna, frequently called Sudan savanna, occurs where there is less precipitation and a prolonged dry season of about five to eight months. As precipitation declines, grass becomes shorter and sparser, and the tree cover less dense. The baobab is the largest tree; it is widely distributed and is valued for its inner bark (from which rope may be made) and its edible leaves and fruits. Other common trees are the silk cotton and locust bean, and various species from the acacia and fig (ficus) families.

Semidesert and Desert

In the semidesert, or steppe, zone that lies between the dry woodland savanna and the desert, annual precipitation is between 250 and 500 mm (10 to 20 in). Rainfall is limited, localized, irregular, and often violent. Semidesert vegetation fringes the Sahara on the south (where this zone is referred to as the Sahel savanna), north (especially the southern slopes of the Atlas Mountains) and east (on the Red Sea coast). It also occurs in Somalia and northeastern Kenya, in the Karoo plateau regions of South Africa, and on the inland margin of the Namib Desert of Namibia and Angola. In addition, the Kalahari Desert is actually a semidesert region, despite its name. In many of these areas, vegetation occurs in strips running along contours in the land, where there has been an accumulation of moisture and soil. These vegetated strips are usually separated by wide barren areas.

With increasing aridity, the drought-resistant properties of plants become crucial for their survival. Trees must be adapted to the prolonged dry period, with deep root systems, thick bark, small leaves that may be shed, and thorns to discourage animals from feeding on them. With still greater aridity, only grasses and desert shrubs survive. Semidesert vegetation is vulnerable to damage from fire, clearing for cultivation, and overgrazing.

Desert vegetation occurs in the Sahara and Namib deserts, areas with less than 250 mm (10 in) of rainfall per year. Desert plant life must adapt to the harsh conditions of sparse, infrequent rainfall and extreme temperatures. The seeds of some species lay dormant for prolonged periods, until there is moisture to support their growth. Large areas of desert are essentially bare; plant growth is concentrated in channels and depressions where water accumulates when it rains. Environmental conditions and species found in the Sahara differ from those in the Namib Desert of southern Africa. In the latter, cold ocean currents facilitate the accumulation of dew on the desert, which helps to support plant life. Succulents (plants that retain water) and annual plant species typically account for most species found in desert ecosystems, with different plant species characteristic of different desert types (sand, gravel, or rock). The arid environments of southern Africa have a remarkable number of different species. Namaqualand, a region in northwestern South Africa, is renowned for the profusion of brilliantly colored wildflowers that appear after spring rains.

Mediterranean Shrub Lands

The shrub lands of the northwestern and southern tips of the continent have Mediterranean climates, with warm, dry summers and mild, rainy winters. Unlike most of Africa, this climate supports distinctive types of temperate plant species. Mediterranean vegetation is xerophytic (drought-resistant), an adaptation to the limited rainfall and prolonged dry season that occurs during the summer months. The tree species typical of the North African shrub lands resemble those found elsewhere around the Mediterranean Sea, including wild olive, cork, juniper, and oak. Large areas of North African shrub lands have been damaged or destroyed through thousands of years of herding and agriculture. Environmental impact was pronounced during the 20th century, when rapid population increase and commercialization encouraged the expansion of agriculture into marginal, environmentally sensitive lands.

The Cape region of South Africa has a distinctive ecosystem known as fynbos, in which fine-leaved evergreen shrubs predominate. It is one of the richest plant life biomes in the world, with some 8,500 species of plants in a relatively small area of about 90,000 sq km (about 30,000 sq mi). Over two-thirds of the species are endemic, meaning that they are found nowhere else in the world. Distinct subtypes of fynbos occur along the coast and in the adjacent mountains. In several other parts of southern Africa infertile soils, fire, and a lengthy dry season constrain vegetation growth.

Highland Vegetation

In Africa’s discontinuous areas of high mountains and uplands, altitude plays a significant role in determining climate and vegetation. On high peaks such as Kilimanjaro, vegetation changes as altitude increases: savanna vegetation near the base, then, in turn, zones of montane forest, bamboo, hagenia, heather, and high-altitude alpine moorland, with rock and ice at the summits of the very highest peaks. The montane forests include hardwood trees and many unusual plant species, including giant heather, giant groundsel, and giant lobelia. Growing conditions are also unusual due to the high temperatures during the day and very low temperatures that prevail at night. Some 4,000 species are associated with the African alpine zone, and three-quarters of these species are found only in Africa’s montane forests.

Other comparatively high-altitude regions have distinctive plant life. The highlands of Ethiopia contain scattered patches of montane forest with many species that resemble temperate deciduous trees. At higher elevations, tree cover largely disappears—except in deep valleys—and grasses, sedges, and heathers prevail. In the highlands of South Africa above 1,100 m (3,500 ft), vast expanses of temperate grasslands occur. In the highest parts of the Ahaggar and Tibesti mountains of the Sahara, some plant species resemble those of the Mediterranean region, isolated there when the region’s climate became drier thousands of years ago.

Soils

Like vegetation zones, soil regions in Africa are closely linked to climatic zones. Rainfall and temperature determine the growth of vegetation, which inhibits soil erosion and enriches soil with nutrients from decaying organic material, called humus. The luxuriant vegetation of tropical forest environments produces large quantities of humus, which is concentrated on the forest floor. In savanna grasslands, humus extends to a greater depth in the soil. The sparse vegetation of semidesert and desert regions gives rise to soils with little organic content. Rainfall and temperature also determine the intensity of chemical weathering, physical weathering, and leaching—all of which affect the development of soil types.

Soil development is highly influenced by the soil’s parent material—the rock from which it is derived—and by topographic relief. Much of Africa’s soil is derived from ancient, quartz-rich rocks that produce generally infertile soils with high sand content. Soils formed in areas of younger volcanic bedrock tend to have higher clay and mineral content, and are therefore more fertile. Relief plays a major role in soil erosion, especially by water. Erosion removes topsoil from upper slopes and deposits eroded materials downslope. These erosion and deposition processes often create a gradation of soil types along a slope. African farmers take advantage of these variations in soil type and soil fertility by planting different crops at different levels of the slope.

Soil-Forming Processes

Hot, humid tropical climates provide ideal conditions for chemical weathering, which gradually brings about the disintegration of parent rock material into soil particles. In drier climates, physical weathering—the breakup of parent material by the force of moving water and wind—is more important than chemical weathering.

Soils in humid tropical regions are especially subject to leaching, the process in which smaller particles and minerals are carried by groundwater downward through the soil. When the upper layers of soil have been leached of critical nutrients, they are left primarily with iron and aluminum compounds, accounting for both their infertility and their typical brick-red or yellow color.

Salinization and calcification are important processes in the development of soils in arid and semiarid regions. Salinization occurs when salts, dissolved in soil water, are carried upward through the soil and deposited on or near the surface as a result of evaporation. Few species of plants are adapted to survive in soils with high salt concentrations. Calcification is prevalent in moderately dry to semiarid environments, generally in grassland areas. Calcification involves development of a subsurface layer of calcium carbonate, carried downward from the upper soil layers.

Major Soil Types

Despite the richness of vegetation, soils in the tropical forests of Central and West Africa are poor. The heavy rainfall of these areas is acidified as it passes through organic material on the forest floor and leaches most of the mineral content from the upper soil layers. The resulting soils—classified as oxisols—are quite infertile, forcing plants to gain most of their nutrient needs from decaying vegetation. Oxisols are reddish or yellowish in color, reflecting the high concentrations of iron and aluminum compounds in them.

The soils of the moist boundary areas between the forests and savanna are subject to high levels of chemical weathering. The resulting ultisols are highly leached (but less so than oxisols), have low to moderate organic content, and are generally infertile.

In savanna regions where there are moderate levels of seasonal rainfall, chemical weathering is less pronounced than in moister environments. Calcification occurs where calcium carbonate levels are high. The resulting soils are called alfisols. The organic content of alfisols is relatively high, and they are generally quite fertile.

In Africa’s arid and semiarid regions, low rainfall and sparse vegetation gives rise to aridisols. These soils are poorly developed, with little chemical weathering, infrequent leaching, and low organic content. Salinization is widespread, resulting in the concentration of mineral salts at or near the surface. In areas with less saline soils, irrigated agriculture is possible. Without proper management, however, irrigated aridisols may become infertile as a result of salinization or waterlogging.

Soils in certain seasonally dry areas are heavy and have a high clay content. The clay in these vertisols expands when it is wet, then shrinks and cracks when dried. These soils are associated with river floodplains and former lake bottoms, notably the middle Nile Valley and Lake Chad Basin. Vertisols are quite fertile due to their high mineral content, and are used extensively to grow cotton and grain crops.

Younger, less developed soils are classified as inceptisols. Included are the thin, rocky soils derived from younger volcanic deposits on the Ethiopian Plateau, young beach deposits in coastal regions, and active sand dunes in semiarid areas. Inceptisols are generally infertile.

Animal Life

Africa teems with animals of all shapes and sizes. The continent has thousands upon thousands of species of mammals, fish, reptiles, amphibians, birds, and insects. Many of these animals are linked in an intricate food web. For example, hippopotamuses deposit large amounts of nutrients in bodies of water where they rest and defecate; these nutrients support abundant growth of plants, insects, and other smaller creatures that in turn provide food for species higher in the food chain. Other animals are linked in symbiotic relationships, such as between big game animals and birds known as oxpeckers. These birds eat the ticks that pester the large animals.

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Continental Forest Animals

African tropical forests offer many niches and habitats for different species. With a wide array of different types of food resources available year-round, they allow large numbers of species to coexist.

Different habitats occur at different heights of the forest. Each of these habitats harbors a distinct set of animal species. The ground layer is strewn with nutrient-rich organic litter, providing a rich environment for many arthropods and insects, as well as creatures that feed on them, such as moles and rats. The forest canopy supports numerous species of mammals, including many kinds of monkeys and flying squirrels. Species of birds, reptiles, bats, and insects also abound. The forest floor tends to be less diverse, although its wildlife includes some of the largest and most fascinating species in Africa, including elephants, lowland and mountain gorillas, and okapis, giraffe-like animals found in the Congo Basin. Other species include duikers, bushbucks, forest pigs, giant pangolins (a type of armored anteater), and drills and mandrills (two species of baboon).

Different areas of the African tropical forest vary in species diversity: For example, the relatively undisturbed forests of Gabon are more diverse than those in Nigeria, where there have been major human impacts on forest ecosystems. Overall, Africa’s forests appear to support less biodiversity than the larger, more heterogeneous forests of the Amazon and Southeast Asia.

Animal Life on Madagascar

Despite its proximity to the continental mainland, Madagascar’s animal life developed in isolation after the island broke away from the rest of Africa about 135 million years ago. It is estimated that 90 percent of the species inhabiting its tropical forests are endemic, meaning that they are found nowhere else in the world. Madagascar has some 25 species of lemurs and 30 species of tenrecs, a type of insectivore. Other native mammal species include several civets and the fossa, a member of the cat family measuring almost 1.5 m (5 ft) in length. Madagascar’s bird and insect populations are equally rich and are also largely endemic.

Because more than 90 percent of Madagascar’s forests have been affected by human activity, many species on the island face extinction because of loss of habitat. Many other notable species have already vanished, including the giant lemur, giant tortoise, and elephant bird.

Savanna Animals

The savannas offer a narrower range of habitats than the forested regions, but nevertheless support exceedingly rich animal populations. The savannas of eastern and southern Africa are renowned for their big game animals, huge herds of herbivores, and abundant bird species. West African savanna regions tend to have less diverse fauna and smaller animal populations, primarily because of long-standing pressures from hunting and loss of habitat. Many species are adapted in particular ways to their environment. Giraffes, for example, have long necks and therefore can graze on vegetation higher than other animals can reach. Because rainfall and food supply are highly seasonal, numerous species are migratory.

Africa is famous for its huge herds of savanna animals. In areas such as the Serengeti Plain in northern Tanzania, herds of herbivores, several thousand zebras or gnus (wildebeests) strong, can stretch for miles. Besides gnus, the savannas support a rich variety of other antelopes, from huge elands to tiny duikers; others include hartebeests, impalas, topis, oribis, kobs, and waterbucks. These animals provide the main food source for carnivores, including lions, leopards, cheetahs, and hyenas. Other species of large herbivores include elephants, black and white rhinoceroses, African buffaloes, giraffes, and hippopotamuses. Many smaller animals, including baboons, several species of monkeys, and a multitude of small carnivores and rodents, are also found.

Africa’s savannas harbor rich bird life. With more than 1,000 bird species, Kenya has one of the most diverse bird populations in the world. Birds of prey, including numerous hawks, eagles, and falcons, feed on smaller birds and other fauna, while vultures seek out carrion as a source of food. Brightly colored rollers, kingfishers, and bee-eaters are commonly seen in the air. Larks and pipits are widespread in the grasslands, as are flycatchers, bulbuls, babblers, warblers, and swallows. Other distinctive birds of the region include the crowned-crane, guinea fowl, ground hornbill, and marabou stork. Some species congregate in huge flocks, among them flamingos and red-billed queleas. The quelea is considered a pest by farmers because of the damage it does to crops.

Savanna regions are also rich in reptile life. Nile crocodiles, as well as other smaller crocodile species, inhabit waterside environments. Various lizards abound, among them large Nile monitors and smaller species of chameleons and geckos. The savannas have many types of snakes, the most feared of which are various species of vipers, as well as cobras and mambas. The rock python is the largest snake, being known to attain a length of 8 m (25 ft).

Desert and Semidesert Animals

Animals in arid environments must adapt to conditions such as water shortages, high temperatures, and a high risk of food scarcity. Some species adapt by migrating to other climes, while others are able to survive for prolonged periods without water. Sizes of animal populations vary from area to area, depending on food abundance; and from time to time, due to unpredictable and scarce rainfall.

Rodent species, including the Nile rat, jerboa, gerbil, and hare, are common in arid and semiarid regions. Several species of gazelles are also found. Rodents and gazelles serve as prey for fennecs, other foxes, jackals, and hyenas. Ostriches, the world’s largest birds, are also found in arid and semiarid regions. Other birds restricted to the deserts and their fringes include sand grouse and coursers.

Freshwater Fish

The rivers and lakes of the northern semiarid and savanna regions—such as the Sénégal, Niger, and Nile rivers, and Lake Chad—have similar fish populations. Several species of catfish and the huge Nile perch are the mainstays of the fishing industry. Some fish species, such as the lungfish, survive the prolonged dry season by burrowing into the mud of drying streambeds and reemerging the following rainy season.

Such is the biological diversity of fish in Lakes Victoria, Tanganyika, and Malawi that biologists consider these lakes critical to the study of evolution. Despite their relatively young age and close geographical proximity, these lakes have developed distinct and highly varied fish populations. Lake Malawi alone has about 540 species of fish—including some 500 species of cichlids—and 99 percent are endemic. To date, 290 species have been identified in Lake Victoria, half of them endemic. Lake Tanganyika has about 140 cichlid and 110 other fish species.

Marine Life

The Atlantic Ocean off Africa’s west coast has two cold ocean currents—the Benguela south of the equator and the Canaries to the north—as well as several areas where cold water rises to the surface. These zones of upwelling are rich in nutrients and support large fish populations. Fishing fleets off the coasts of southern and northwest Africa harvest species such as sardines, herrings, and tuna. Shrimp are harvested on the coasts of several West African countries.

The waters of the Red Sea and Indian Ocean are considerably warmer than those of the Atlantic, supporting the development of coral reefs. These reefs provide for a great variety of fish species. Local fishers harvest many types of fish, but large-scale commercial fishing remains relatively unimportant. One famous rare species of Indian Ocean fish is the coelacanth, characterized as a “living fossil.” Before it was discovered in 1938, experts believed it had been extinct for 70 million years.

Insects

Africa has a vast insect population. As on other continents, insects play a critical role in African ecosystems. Some insects are of particular importance to humans as either transmitters of diseases, soil modifiers, or threats to crops.

Insects as Carriers of Disease

In colonial times, Europeans referred to Africa as the “white man’s grave,” reflecting the fear of life-threatening tropical diseases for which non-Africans lacked natural resistance. The leading cause of death—among colonists and Africans alike—was malaria. The malaria parasite is transmitted to humans by the bite of the female Anopheles mosquito. The World Health Organization (WHO) launched a worldwide campaign to eradicate malaria during the 1960s by spraying homes with insecticides, draining breeding sites, and dispensing antimalarial drugs. The campaign failed: Parasites developed genetic resistance to drugs, mosquitoes became resistant to insecticides, and impoverished governments lacked the resources to develop a comprehensive strategy against the disease. Today, malaria remains Africa’s leading cause of death.

Various species of tsetse fly are another scourge of Africa. The tsetse transmits the Trypanosoma parasite, which causes the often-fatal disease trypanosomiasis, also known as sleeping sickness in humans and nagana in livestock. The prevalence of tsetse is believed to be a major factor in settlement patterns in Africa, including the low population densities of large areas of the savanna. Because cattle are especially vulnerable to trypanosomiasis, the full economic potential of vast areas of fertile grassland has not been realized. Certain colonial policies heightened the tsetse scourge: The creation of game reserves increased populations of wild animals that serve as natural reservoirs of the Trypanosoma parasite; and resettlement schemes increased human contact with tsetse and brought about major epidemics of sleeping sickness. An epidemic in the early 20th century wiped out some two-thirds of the population of what is now Uganda. Colonial control programs eventually succeeded in limiting, but not eliminating, the tsetse and the diseases it transmits.

The black fly Simulium damnosum has had a major impact on settlement in Burkina Faso and several other countries in West Africa. This insect, which breeds in fast-flowing streams, transmits a parasitic worm that is responsible for onchocerciasis, also known as river blindness, which causes blindness and severe skin problems. As rates of infection and blindness increased in villages close to fly-breeding sites, local economies were weakened and eventually the village sites were abandoned. The WHO initiated a control program during the 1970s, using insecticides to kill larvae of the fly, and chemotherapy to treat infected people. This program has succeeded in interrupting the transmission of the disease in most of the affected areas.

Termites

The forests and savannas of Africa are home to some 400 species of termites. Termite mounds vary in size, depending on the termite species and on soil conditions: Some may be up to 9 m (30 ft) tall, with nests extending up to 15 m (50 ft) underground. Vast numbers of termites inhabit these nests; densities as high as 9 million termites per hectare (4 million per acre) have been recorded.

Termites are both friend and foe to humans. Termite colonies enhance soil fertility by transporting and concentrating fertile subsoil clays near the surface and by increasing soil aeration. African farmers seek out termite mounds and plant crops around them—yields are usually higher from crops in these sites. Conversely, termites consume vast quantities of organic matter, and are blamed for increased soil erosion that may occur around termite mounds.

Locusts

Three main types of locusts are found in the dry savanna and semidesert areas of Africa: the desert locust and the African migratory locust, found north of the equator, and the red locust, which occurs in south central Africa. These locusts occasionally congregate in large swarms to migrate in search of food. Following the direction of prevailing winds, they devour everything green in their path, including entire crop harvests. Spraying programs to control populations and routine monitoring to detect the first signs of swarming have reduced the serious threat that locusts once posed to agriculture. However, locusts can still sometimes cause significant damage at a local or regional scale.

Environmental Issues

Africa is widely seen as a “devastated continent,” where inappropriate human use of land has caused deforestation, desertification, and soil erosion on a massive scale. This view of Africa has greatly influenced academic research agendas and international aid programs, as well as public perceptions of the continent. But some scientists are increasingly questioning this view of environmental degradation. They emphasize the need to ascertain whether degradation is actually occurring, how human actions affect the process, and what conservation measures are needed. In some cases, Western viewpoints and ideas have led to misguided attempts at conservation that had no effect or even an adverse effect on the environment. At the same time, some African conservation methods were discovered to be much more effective. Going forward, many experts argue that conservation strategies must be sensitive to regional and temporal variations and should seek to preserve and build upon local indigenous knowledge.

Soil Erosion and Desertification

Until recently, there was widespread consensus among scientists and policymakers that African soils were threatened by ill-advised traditional farming methods that increased soil erosion and desertification (the process in which soil dries out until almost no vegetation grows on it). Policy documents used limited, often flawed case studies to produce continent-wide generalizations in which worst-case scenarios were too often presented as typical. In reality, the nature and extent of soil erosion and desertification varies greatly throughout Africa and much of it is unrelated to human activity. For example, savanna regions are subject to wind erosion in the dry season, which is the primary cause of soil erosion in arid and semiarid environments.

The Sahel, a semiarid savanna region located to the south of the Sahara, experienced a severe drought from the late 1960s to the early 1970s. In reaction, Western scholars propagated a popular view that the Sahara was expanding year by year, relentlessly enveloping once-productive land. Further research has shown that, while soil degradation was confirmed in some areas, in many parts of the Sahel there was little evidence of degradation, and none of steady desert expansion. During the colonial era, the perception of imminent crisis led to policy initiatives designed to preserve the soil. Colonial administrators attempted to control the perceived problem of erosion by enforcing restrictions on herding and agriculture, restricting the use of fire to clear land for agriculture, and installing grass and stone barriers along slope contours. These measures were generally resented by the local African population, and they had little impact on erosion rates. Similarly, attempts to control desertification through policies such as planting shelter belts of trees and restricting nomadic herding have had limited effect.

Scientific research has demonstrated that indigenous African farming and herding practices are much less harmful to the soil than was formerly believed. Methods such as retaining farmland trees, growing crops on ridges, and interplanting different crops densely in a single field significantly reduce soil erosion. On the other hand, modern cultivation methods—involving the use of mechanical equipment, row cropping, and weed control with herbicides—greatly increase the risk of soil loss. Similarly, problems of soil erosion and degradation are greater in areas with fenced cattle ranches than in places where traditional livestock practices are followed, with animals grazing less intensively over a very large area.

Human Impact on Vegetation

Little of Africa’s vegetation is natural in the sense of being virtually unaltered by humans. Areas near settlements bear the particular marks of human impact: People plant trees for fruit, shade, and other uses; preserve beneficial wild species; and selectively clear less desired vegetation.

Humans have had a major impact on the loss and degradation of Africa’s tropical forests. Between 1990 and 2000 an estimated 5 million hectares (13 million acres) of forest were lost in Africa. The destruction has been especially significant in Madagascar and in West African countries such as Nigeria, Ghana, and Côte d’Ivoire, where population growth and agricultural development have been rapid and forest area is relatively small. Economic development schemes have harmed forests in many countries. Forests have been cleared for large-scale plantation agriculture, flooded under reservoirs by the construction of dams, and, in the case of the Niger Delta, harmed by development and pollution related to petroleum exploitation.

While agricultural expansion has resulted in forest loss in many areas of Africa, traditional agricultural practices are not necessarily the cause. Recent studies in Guinea have documented significant expansions of forest cover during the 20th century through the deliberate interventions of humans, including the strategic burning of patches of forest. When practiced in moderation, burning helps replenish soil with nutrients from burnt vegetation and provides new seedlings with the space to flourish. Similar results have been found elsewhere in West Africa.

Threats to Freshwater Ecosystems

Overfishing, pollution, habitat changes, and the ill-advised introduction of exotic species all pose a significant threat to the biodiversity of Africa’s major lakes and rivers. Human impact has been especially severe in Lake Victoria. Signs of overfishing—declining size and volume of catch—have been evident in the lake since the 1920s. One response was to introduce new species to enhance the fishing industry: Four species of tilapia and the Nile perch were released into Lake Victoria in the 1950s and 1960s. While the fisheries initially benefited, the ecosystem was devastated. The Nile perch displaced the traditional predators, and by the 1990s about 60 percent of Lake Victoria’s cichlid species had become extinct. Many rivers and lakes—particularly Lake Victoria—have also suffered from the introduction of the water hyacinth, a large ornamental water plant native to South America. The water hyacinth spreads rapidly and threatens fish and other water life in the rivers and lakes by depriving them of oxygen and causing significant changes in aquatic habitats.

Wildlife Conservation and Management

Africa’s animal life is under pressure, facing threats that include habitat loss from forest clearance, agriculture, and herding; hunting for food and profit; pollution from agricultural and industrial sources; and disturbance by tourists. As spaces for wildlife shrink and corridors linking areas of habitat are cut, the survival of healthy species populations—especially of larger animals and highly specialized species—becomes more tenuous. Addressing these problems is a very complex issue, especially because indigenous peoples have diverse needs for, and claims to, these resources. Thus, the need for protected spaces for wildlife often seems at odds with human needs.

Wildlife protection has had a long history in Africa. Colonial conservation measures were imposed on African societies without consultation or consideration of the impact on local economies. Indigenous conservation measures, practiced for centuries, were ignored and sometimes undermined. In more recent times, threats to habitat and to wildlife have come increasingly from large-scale projects, such as dams, reservoirs, and irrigation schemes. Yet the solutions proposed to protect wildlife have generally continued to impose significant costs on local communities.

Game reserves were first established by Africa’s colonial rulers in the 1890s. Concern about the effects of hunting on big game led to the establishment of several national parks for wildlife conservation in the 1930s. The establishment of new parks and reserves continued throughout the colonial era, and postcolonial regimes followed suit. A sometimes uneasy mix of conservation and economic concerns—especially tourism—continues to provide the rationale for such initiatives. Some 5 percent of Africa’s land area is designated as protected. However, protected areas vary between countries: While 30.2 percent of Botswana is designated as protected, the figure is only 2.6 percent for Madagascar. Also, some environments, such as semidesert and marine sites, remain underrepresented.

Indigenous populations often remain ambivalent about wildlife conservation programs that restrict their access to farmland and pastures and set limits on killing wild animals for food. Governments have begun to experiment with comanaged protected areas, in which local communities are consulted about decisions, given priority access to jobs as guards and guides, and allowed limited access to the protected areas for hunting and other activities. The objective of these programs is to ensure that local communities feel they have a stake in successful conservation. The most effective

of these programs—notably, Zimbabwe’s Communal Areas Management Programme for Indigenous Resources (CAMPFIRE)—have succeeded in reducing poaching and increasing local incomes.

There has been much controversy over the best way to stop the poaching of big game animals, particularly elephants, which are killed for their ivory tusks. In 1989 the Convention on International Trade in Endangered Species (CITES) voted to enforce a total ban on the ivory trade. Kenya and other African countries that had been severely affected by poaching were strong supporters of this ban. On the other hand, South Africa, Zimbabwe, and Botswana argued for limited elephant hunting and a controlled ivory trade as the best way to protect elephants. These countries have large and growing elephant populations, and have traditionally culled their herds periodically to maintain the health of herds and of the ecosystems supporting them.