Biodiversity in Africa

April 19, 2011, 8:31 pm
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Biodiversity offers multiple opportunities for development and improving human well-being. It is the basis for essential environmental services upon which life on Earth depends. Thus, its conservation and sustainable use are of critical importance.

The opportunities and challenges associated with biodiversity typically apply over large geographical extents, although one or two issues may be more important at any given location. To avoid repetition, particular issues are highlighted in the sub-regional sections, not because they are restricted to those areas, but because they are best illustrated there. Deforestation is discussed under Central Africa, while relations between protected areas and adjacent populations are dealt with under Eastern Africa. Riparian biodiversity is discussed in Northern Africa, climate change and invasive alien species (IAS) in Southern Africa, desertification in Western Africa, and endemism in the Western Indian Ocean (WIO) islands. Habitat degradation and resource overexploitation are discussed in this regional synthesis, because they are overwhelmingly important as drivers of biodiversity loss throughout Africa.

Inventory of resources

Africa is well endowed with both variety and abundance of living things, together referred to as biological diversity, or biodiversity. That biodiversity, with some exceptions, is currently in a better condition than in many parts of the world. Biodiversity can be considered at three major levels:

• The genetic variation within populations;
• The number, relative abundance and uniqueness of species; and
• The variety, extent and condition of ecosystems.

Ecosystems are broadly arranged in a latitudinal pattern, with increasing species richness towards the equator. However, plant species richness is also high in the winter-rainfall Mediterranean climate regions of Northern Africa and the southern Cape. In between are the subtropical deserts, which are generally a zone of lower diversity: for example, a vast part of the Sahara, the Ténéré, is home to only 20 plant species in an area of about 200,000 km2. Overlaid on these latitudinal patterns are pockets of rich biodiversity with small distribution ranges, particularly in tropical montane areas. From Ethiopia to the Cape, mountains contain several centres of endemism for birds, mammals, and plants. One of the most globally important centres of endemism is the coastal mountain range in the eastern part of Madagascar.

The increasing richness of plants and vertebrates toward the equator is related primarily to climatic factors, such as water availability, however the diversity of land variations, such as topographic, is also important. There are exceptions to this: some areas with harsh climates including, the Namib Desert and the Karoo in the west of South Africa have an estimated 4,500 plant species, a third to one-half of which are endemic.

Spatial patterns of diversity vary for different species, and the diversity and abundance of different species influence each other. For example, the Cape is a centre of plant diversity of global importance, but not a centre of diversity for mammals, birds, snakes and amphibians (Figure 1). The Central Zambezian Miombo woodlands located in Zambia, the Democratic Republic of the Congo (DRC) and Tanzania is a centre of bird diversity, but not of plant diversity.

Species richness and endemism

About 1000 vertebrate species occur in just four of Africa's 119 ecoregions (covering about eight percent of Africa’s total land area): Northern Acacia-Commiphora bushlands and thickets, Northern Congolian forest-savannah mosaic, Albertine Rift montane forests and Central Zambezian Miombo woodlands.

A quarter (1,229 species) of the world’s approximately 4,700 mammal species occur in Africa, including about 960 species in sub-Saharan Africa (SSA) and 137 species in Madagascar. The eastern and southern savannahs host large populations of mammals, including at least 79 species of antelope.

More than 2,000 bird species occur, constituting more than a fifth of the approximately 10,000 bird species in the world. About 1,600 bird species are endemic to SSA. Bird species richness is highest in Eastern Africa around the Albertine Rift montane forests, the Victoria basin forest-savannah mosaic, East African montane forests, Northern Congolian forest-savannah mosaic, and then into the Acacia-Commiphora bushlands and thickets and the Central Zambezian Miombo woodlands. The large size of these eco-regions, their high level of habitat heterogeneity, and their presence on a migratory flyway explain this pattern. The next highest band of species richness is found across the remainder of the tropical belt, with the exception of the western portion of the Upper Guinea forests and the centre of the Congo basin. The eco-regions of Madagascar and other offshore islands all have much lower bird species richness than the continental mainland.

Africa has about 950 amphibian species; however numerous new species and even genera are described every year. The highest levels of amphibian species richness occur in the DRC (210), Cameroon (189) and Tanzania (157); these countries are also ranked among the 20 countries with the highest level of diversity and endemism. The fauna of Madagascar are particularly undersampled: from 1990 to 1999 discoveries of new amphibian and reptile species increased the number of known species by 25 percent and 18 percent, respectively. The Congo basin is also under-represented due to inadequate surveys.

Overall plant richness at species, genus and family level is lower than that of other tropical areas. The African mainland has between 40,000 and 60,000 plant species, of which approximately 35,000 are endemic. South America, by comparison, has about 90,000 plant species in an area 40 percent smaller. Parts of the Congo basin have moderate levels of plant species richness, comparable to many parts of Central Europe. This is a consequence of major extinction events due to historic climate variations and fewer major tectonic events, which are thought to having triggered the evolution of many species in the South American Andes. Five of the 20 global centres of plant diversity are located in Africa. More than 3000 plant species per 10,000 km2 occur in the Cameroon-Guinea centre, the Capensis centre, the Maputaland-Pondoland centre, the Albertine Rift centre and the Madagascar centre.

At least a sixth of the world’s plant species are  to Africa. The Cape Floral Kingdom, a global centre of plant endemism has about 9,000 vascular plant species occurring in an area of 90,000 km2 of which about 69 percent are endemic. More than 12,000 plant species occur in Madagascar, at least 81 percent of which are endemic, which is an exceptionally high proportion by global standards. More recent studies suggest that these figures for species richness and endemism in Madagascar may be underestimates.

Southern Africa has a rich and varied insect and arachnid fauna, with at least 580 families and about 100,000 species recorded. There is a high diversity of butterflies in the rainforests of the upper Guinea, the Albertine Rift, and the Congo basin, as well as in the Central Zambezian Miombo woodlands. Namibia is thought to be one of the global centres of arachnid richness and about one-third of the Southern African insect species are believed to occur in Namibia, although less than a quarter of these species are described.

Africa has several global centres of freshwater biodiversity and many of these are also centres of intensive fishing activity. Centres of species richness and endemism for freshwater fish, molluscs and crustacea are located in the upper Guinea river region (mainly Guinea and Liberia), Cabinda (DRC), and the eastern part of Madagascar. It is conservatively estimated that Africa has at least 2,000 fish species, which is thought to be the highest species richness in the world. The explosive diversification of certain types of fish, such as the Cichlidae in the Great Lakes, has contributed to this richness. Fish species richness in the Congo basin is second only to that of the Amazon basin. Data on endemism is inadequate. Fish diversity at the family level is somewhat lower than in southern America and Southeast Asia.

The coastal and marine ecosystems along Africa’s 40,000 km coastline contain a high marine biodiversity, with overlapping centres of endemism of, for example, fish, corals, snails and lobsters at the coast of eastern South Africa and in the Red Sea.

Centres of biodiversity

Biodiversity information is patchy for many organisms. Centres of biodiversity are located in the following ecoregions: Mt Cameroon and Bioko montane forests, overlapping with the Cross-Sanaga-Bioko coastal forests; the Cameroon highlands’ forests; the Eastern Arc forests and the northern Zanzibar-Inhambane coastal forest mosaic; the Guinea montane forests and the western Guinea forests; the Drakensberg montane grasslands and forests; the Albertine Rift montane forests and the upper Guinea lowland rain forests.

Nearly two-thirds (62 percent) of SSA species of plant and vertebrates can be represented (though not necessarily adequately protected) in approximately 1 percent of its land area, as shown in Figure 3. This 1 percent area includes key taxon-specific centres of diversity (such as the Cape for plants) and a few multitaxon centres of biodiversity such as, for example, Mt Cameroon, East Usambaras, Mt Nimba, Western Ruwenzori, Mt Elgon and parts of the upper Guinea lowland forests. Many of the represented species are endemic to these areas. To include all vertebrate and plant species occurring in SSA in protected areas, about a third of its total area would need to be included into conservation strategies. Hence, identifying locations of high biodiversity in several major groups, so that a high proportion of biodiversity can be protected in a comparatively small area, is an important research goal.

Ecosystem change and conservation

In comparison with most other parts of the world, such as eastern Europe, North America and Southeast Asia, Africa’s biodiversity is still in good condition. Contemporary biodiversity patterns are strongly influenced by land-use patterns of mammalian herbivores and people. However:

• Approximately half of Africa’s terrestrial eco-regions have lost more than 50 percent of their area to cultivation, degradation or urbanization.
• Eco-regions that have gone through more than a 95 percent transformation include the Mandara Plateau mosaic, Cross-Niger transition forests, Jos Plateau forest-grassland mosaic, and Nigerian lowland forests.
• Nine other eco-regions have lost more than 80 percent of their habitat, including the species-rich lowland Fynbos and Renosterveld and the forests and grasslands of the Ethiopian Highlands.
• The Mediterranean woodlands and forests have lost more than 75 percent of their original habitat, and the few remaining blocks of habitat are highly fragmented.

The challenges and opportunities associated with human activities are also considered in relation to specific themes in the other chapters of this section.

Africa has over 2 million km2 of protected areas (an area four times the size of Spain). The eco-regions under the best protection tend to be the savannah habitats, particularly those of Eastern and Southern Africa. Charismatic animals, such as large mammals, are much better covered by the current network of protected areas than, for example, plants. Many range-restricted species are not adequately included in these areas.

The least protected areas are found in Northern Africa, Madagascar, the drier parts of South Africa, and in the most heavily deforested parts of Western and Eastern Africa. Of the 119 ecoregions, 89 have less than the 10 percent of their area officially protected, which is the guideline suggested by the 2010 biodiversity targets of the Convention on Biological Diversity (CBD). Some of the least well-protected eco-regions are also those with high biodiversity values, including Mt Cameroon and the Bioko area, the Eastern Arc forests, the Succulent Karoo, the Ethiopian montane forests, the lowland Fynbos and Renosterveld, the western Guinean lowland forests, the east African montane forests, the Albertine Rift montane forests, and the Northern Zanzibar-Inhambane coastal forest mosaic.

Endowments and opportunities

The least protected areas are found in Northern Africa, Madagascar, the drier parts of South Africa, and in the most heavily deforested parts of Western and Eastern Africa. Of the 119 ecoregions, 89 have less than the 10 percent of their area officially protected, which is the guideline suggested by the 2010 biodiversity targets of the Convention on Biological Diversity (CBD). Some of the least wellprotected eco-regions are also those with high biodiversity values, including Mt Cameroon and the Bioko area, the Eastern Arc forests, the Succulent Karoo, the Ethiopian montane forests, the lowland Fynbos and Renosterveld, the western Guinean lowland forests, the east African montane forests, the Albertine Rift montane forests, and the Northern Zanzibar-Inhambane coastal forest mosaic.

There is a considerable overlap between historic cultural centres and centres of biodiversity. Some factors promoting high biodiversity, such as perennial water availability, environmental heterogeneity and fertile soils have also favoured human settlement. In general, patterns of biodiversity and language diversity coincide, and show parallel extinction risks, suggesting that cultural cohesion and biodiversity sustainability are closely linked.

The most important centres of vertebrate and plant diversity are inhabited by more than 100 million people and are areas of intensive land use. These have been identified as “hotspots”. In Africa, these are the Cape Floristic Region, the Coastal Forests of Eastern Africa, the Eastern Afromontane, the Guinean Forests of West Africa, the Horn of Africa, Madagascar and the Indian Ocean Islands, Maputaland-Pondoland-Albany and the Succulent Karoo. Despite their proximity to metropolitan areas and despite often being completely surrounded by transformed land, many sites of primary vegetation remain within hotspots (for example, the Taï and Banco national parks of Côte d’Ivoire, the Table Mountain National Park of South Africa, and parts of the coastal forests of Eastern Africa); these areas contain irreplaceable habitats for endemic species. For example, the Taï National Park currently represents at least 40 percent of the total remaining forest area of Côte d’Ivoire.

There are at least two fundamental reasons for Africa’s biodiversity richness:

• First, it has occupied its position astride the equator for hundreds of millions of years. Its life forms have not, during this period, been wiped clean by glaciers or inundated by oceans, and have been able to gradually accumulate new varieties.
• Second, perhaps because Africa has been occupied by humans for longer than any other continent, it has not suffered the mass extinctions that followed the arrival of the human species elsewhere.

In this place where humans evolved, people coexisted with other living things, at least until the modern era. That situation is rapidly changing. Major increases in the human population and rising wealth create pressures on land, and on freshwater and marine ecosystems. Global trade has intensified the demand for animal products, tropical timbers, cash crops and seafood. At the same time, global connectedness has brought new problems, such as global climate change, IAS, the spread of viral diseases, and the introduction of new technologies. The result is that biodiversity, so persistent for millions of years, is now under unprecedented threat. These human drivers and pressures are discussed more fully in the Human dimension of development in Africa.

Biodiversity underlies the provision of a large variety of benefits that people obtain from ecosystems. These include environmental goods, such as food and wood for energy, and ecosystem functions that depend on particular organisms, for example pollination by bees, or nitrogen fixation by symbiotic bacteria in the roots of legumes. Living organisms are critical in creating the environmental conditions on Earth that make it habitable to humans and many other species by, for instance, regulating the climate and atmospheric composition.

Environmental goods

Many important food crops originate in Africa, including several species of millet and sorghum, one species of rice, the grain crop teff, and the oil palm. Globally, about 7,000 of the 270,000 known plant species have been used as food (FAO 1997), but only about 200 have been domesticated, and just 20 of these are of major economic importance. About two-thirds of the overall calorie intake is provided by ten crops. Globally, only 30-40 species (0.25 percent of 15,000 species of mammals and birds) have been used extensively in livestock production, and fewer than 14 account for over 90 percent of livestock production. African biodiversity is closely linked to nutrition and achieving food security. Nearly three-quarters of the recorded protein consumption in Africa is derived from plant sources. In rural areas, essential micronutrients are derived from eating a large variety of plant foods. Foods from the wild are particularly important in times of stress – drought, illhealth and economic change – and, as discussed in Genetically modified crops in Africa, shifts to monoculture may present threats to biodiversity, human health and food security. Much of the animal protein consumed is either directly harvested from wild populations (fisheries and bushmeat), or produced through grazing of natural ecosystems by domestic livestock. Freshwater fish is a key source of protein. For example, in hyper-arid Mali, fish makes up 60 percent of the total animal protein consumed annually. In Central and Western Africa, bushmeat (wild animals and birds) is a major source of animal protein, making up more than 80 percent of consumption in some areas. Milk, often in sour form, is also an important protein source.

Freshwater fisheries, such as those at lakes Victoria, Tanganyika and Malawi, support subsistence livelihoods and enterprises at multiple levels. Wetland systems, including those of Lake Banguelu, the Kafue floodplain and the Okavango delta, are also important sources of food. Important commercial marine fisheries are located off the west coast of Southern Africa (South Africa, Namibia and Angola), the Horn of Africa, and off the coast of Mauritania in Western Africa; collectively these provide about half of the total catch. These fisheries are centred on commercially important species such as hake, anchovy and pilchard, and the associated industries are an important source of employment.

Forests and woodlands provide a wide range of environmental goods. Over 80 percent of people rely on wood or charcoal for domestic cooking and heating, as processed fossil fuels are too expensive. Charcoal tends to be preferred in most urban areas, as the energy content per unit mass is about double that of wood. Charcoal is also cleaner-burning at the point of consumption than wood, so that the health impacts of charcoal are about four times lower than that of wood, but the total greenhouse gas (GHG) emissions (including the making of the charcoal using earth kilns which are not efficient) are higher. Forests and woodlands also provide poles, bark string and thatch for houses and livestock pens. Especially in rural areas with only a partial cash economy, natural ecosystems are the main source of building material, which would be unaffordable if it had to be purchased. Several forest and woodland species are important as commercially traded timber, especially for the furniture industry. These include species such as Pterocarpus angolensis and Melia. Most of these species are harvested from natural ecosystems, although some are now being established as plantations.

Natural ecosystems provide a wide variety of plants and animals that are important for traditional medicines and modern pharmaceutical products. Up to 80 percent of people make some use of traditional medicine, which draws on a wide variety of indigenous plants and animals, and especially on rare or unusual organisms. Important modern pharmaceutical products are derived from certain plants. For example, the Namibian devil’s claw (Harpagophytum procumbens) is used locally for digestive problems, arthritis and low back pain, and supports lucrative trade. The bark of the afromontane tree Prunus africana is the source of a commercial prostrate remedy.

Pharmaceutical bioprospecting is likely to increase in coming years, especially as new methods that utilize evolutionary and ecological knowledge enhance productivity. The 2004 global market for herbal medicines, including herbal products and raw materials, was estimated to be US$65,000 million. As a source of income, medicinal plants compare favourably with coffee, oil palm, cocoa and cotton, and they do not appear to be affected by the Organisation for Economic Cooperation and Development’s (OECD) market and trade barriers which affect other commodities from developing countries. Rural communities have a great opportunity to effectively use their local knowledge to become serious players in the global herbal medicine market. Many plants and animals originating in Africa are important commercial trade products. Coffee (Coffea arabica and Coffea robusta) originates in Ethiopia and ranks among the five most valuable agricultural exports from developing nations, employing about 25 million people worldwide. Aspalathus linearis (Rooibos tea), originating from South Africa, is now traded globally in the fast-growing speciality tea industry. The world’s ornamental flower market includes a substantial number of species derived from Africa: Gladiolus, Pelargonium, Geranium, Strelitzia, Viola, Protea, Kniphofia and Zantedescia. The growing international pet trade includes several African species, including many endemic cichlid fish species from Africa’s rift valley lakes for aquariums. Key trade-related concerns include: the illegal (and often wasteful) harvesting from wild populations of often rare species; the accrual of benefits to individuals, whereas the costs are borne by society as a whole; and international intellectual property rights and patent agreements which can deprive local people of benefits. Currently, relatively little of the value derived from species originating in Africa accrues to Africa. Ensuring that such benefits are captured in future represents a major opportunity for expanding biodiversity-based development. Environmental services Biodiversity has “intrinsic value” – or value for its own sake – but it also has significant value in all cultures for the things that it provides: food, medicine, building and craft materials and spiritual, cultural and aesthetic services. Less obvious, but just as important, are the services that allow natural and human-altered ecosystems (such as agricultural and urban landscapes) to function properly – regulating the climate, soil fertility, and the outbreak of pests and diseases. Some level of biodiversity – the exact amount is at this stage unknown – is a necessary condition for the delivery of ecosystem services, but it is especially important for maintaining functional ecosystems. The value of ecosystem services can sometimes be expressed in monetary terms but these estimates are very contentious, and are not the only way of expressing importance. Value can, for instance, be measured in terms of other aspects of human well-being, such as health, security or good social relations. Ecosystem services depend not so much on the absolute number of species present, but on the diversity of the functions performed by different members of the ecological community. The preservation of the natural biodiversity of an area and genetic diversity of crop species can enhance resistance to invasion by pests and diseases thus reducing agricultural losses. Planting a variety of crop species and varieties, and preserving their wild relatives, increases crop resistance to pests and diseases and thus the probability of meeting food needs. Ethiopia and the Upper Nile are recognized as global centres of crop plant genetic diversity. Agro-biodiversity farming practices can enhance biological control and reduce the dependency and costs associated with biocides in monocropping systems. Similarly, natural and semi-natural ecosystems, both terrestrial and marine, appear to be more resistant to IAS if the number, types and relative abundance of native species are preserved. Biodiversity can provide pollution detoxification and control. Certain aquatic and marine organisms provide water filtration services that significantly reduce the impacts of pollution on water quality. For example, the hydrological processes in wetlands, and particularly the water velocity reduction by vegetation and the creation of anaerobic zones, bring about the deposition of heavy metals from streams and rivers, reduction in nitrogen loading through denitrification, and reduction of pathogens through predation by other microorganisms. Well-vegetated watersheds significantly reduce the volume of sediment transported by rivers. Protecting the ecosystems and organisms that provide such services is generally far more cost-effective than the alternative of building and operating water filtration plants. In the context of the oceans, some marine microbes can degrade toxic hydrocarbons such as those released in an oil spill, providing valuable pollution processing services. Ecosystem biodiversity – both terrestrial and marine – influences climate at local, regional and global scales. The type and distribution of habitats and the functional diversity of terrestrial plants influence the reflection of incoming radiation from the sun back to space, evapotranspiration, air temperature, fire regime and carbon sequestration, all of which influence climate. It has been suggested that human-induced changes to the vegetation in the semi-arid Sahel has contributed to decreased precipitation since the 1970s and to desertification. Marine biodiversity plays a major role in climate regulation, particularly through its effects on nitrogen cycling and carbon sequestration. If there were no life in the ocean, transfer of carbon dioxide from the atmosphere to the sea floor would cease, and atmospheric carbon dioxide levels would rise. Recreational and spiritual values People of all cultures and income levels value the cultural, spiritual, religious, educational and aesthetic benefits of biodiversity . Traditional societies express these values in the form of sacred species, ecosystems and landscapes, while urban and developed societies express this in the form of protected areas and heritage sites. Many religions attach spiritual values to ecosystems or components of ecosystems, such as trees, hills, rivers or groves. Loss or damage to ecosystems can therefore harm social relations by, for example, impeding religious and social ceremonies that bind people. Biodiversity also has intrinsic value for many people: it is valued as an end in itself, apart from any use value that it provides to people. Nature-based tourism Nature-based tourism is one of the fastest-growing tourism sectors worldwide and in Africa. It depends on the conservation of natural landscapes and wildlife, so that using ecosystems in this way can jointly promote human well-being and biodiversity conservation if well managed. International tourism represents about 7 percent of the worldwide export of goods-and-services, ranking fourth after exports of chemicals, automotive products and fuels . Nature-based tourism makes up approximately half of the total tourism market. The significance of this sector is discussed more fully in Land resources in Africa and Coastal and marine environments in Africa. Adding value to genetic resources Genetic resources include all chemical and genetic information of substances that could be used as biochemical precursors in the synthesis of pharmaceutical or agricultural products. Selecting substances for investigation often depends on traditional knowledge about which plants or animals are used for specific purposes. There is a substantial global market for pharmaceutical value-addition to genetic resources. Global sales of pharmaceuticals amounted to US$300,000 million in 1998. Of the 25 percent best-selling drugs worldwide in 1997, 42 percent of sales came from biological or natural products, or entities derived from natural products, with a total value of US$17,500 million. Despite the technical progress in the development of fully synthetic drugs, 11 per cent of the 252 drugs considered as basic and essential by the World Health Organization (WHO) originate exclusively from flowering plants. The pharmaceutical industry is highly researchintensive. Of the average expenditure of US$500 million on the development of a new drug, about 37 percent is spent during the “discovery phase”. Of the approximately 120 pharmaceutical products derived from plants in 1985, 75 percent were discovered by studying their traditional medical use. Traditional African cultures have a deep knowledge of their natural environment, sometimes accumulated over thousands of years.

A second important market for genetic resources is the agro-industry. Responding to global and regional market and financial pressures, farmers now grow a limited number of high-yielding varieties of food crops. This may result in higher income in the short term, but makes production more susceptible to disease or environmental problems, and more dependent on fertilizers and pesticides. Cultivars of many of the world’s most important economic plants stem from a very narrow genetic base. For example, plantations of oil palm in Malaysia are based on material from only four specimens of this plant from Western Africa. Considerable efforts are therefore underway to broaden the genetic bases of crops through the introduction of varieties to increase resilience and maximize productivity. Typically, the development and release of a new, modern variety takes 8-15 years and costs in the range of US$1-2.5 million, for a traditionally bred variety, and US$25-75 million to develop a transgene for genetically modified (GM) varieties. However, the wild relatives of many important food crops are fast disappearing. For example, Ethiopia, which is the geographic origin of coffee and is a centre of genetic diversity, is one country whose biodiversity has been least explored, but has only 4,000 km2 of land containing populations of wild coffee remaining. Many other populations of wild species are increasingly restricted in distribution and fragmented, and nine species for mainland Africa were listed as threatened in 1998.

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Glossary