Previous:Wetlands Management ||Table Of Contents|| Next: Agriculture

BIOLOGICAL RESOURCES AND DIVERSITY

The Zambezi Basin has four main biomes, or large ecological regions characterised by similar climate, vegetation and species, across the basin: Congolian, Zambezian, Montane and Coastal. Lake Malawi/Nyasa can be added as a fifth, but only as regards aquatic organisms such as fish associated with this deep-water lake.

There are no major centres of endemism or particular "hot spots" for most groups, apart from Lake Malawi/Nyasa for aquatic organisms, although the montane and moist forest habitats support some species not found elsewhere in the basin.

• The basin has a total number of 200 mammals.
• The birds of the basin are comparatively well known. There are about 700 species of birds recorded of which only 15-20 are endemic to the basin, including the Black-cheeked Lovebird and the Slaty Egret. Of these, 167 are wetland-related. The wetlands and other habitats of the Zambezi Basin are important sites for Afrotropical and Palaeoarctic migrants, consisting of about 70 and 90 species, respectively.
• The fish species of the basin have been fairly well documented, principally owing to their economic interest, although details of the fish diversity of the Zambezi Delta are still scanty. There are about 165 species of freshwater fish recorded from the basin in addition to more than 500 endemic species (mostly cichlids) in Lake Malawi/Nyasa.
• There are 200 species of reptiles and about 90 species of amphibians recorded. Only very few are endemic to the basin or areas in it.
• Invertebrate biodiversity is not well known in the Zambezi Basin except for groups such as dragonflies, butterflies, freshwater molluscs, dung beetles and grasshoppers/crickets. In addition, groups of particular economic interest - mosquitoes and tsetse fly, locusts, ticks and agricultural pests - have been the focus of detailed research. The number of species of insects and other invertebrates present in the basin is unknown, but it is likely to be in tens if not hundreds of thousands.
• Dragonflies are a group of insects that are principally confined to water and wet places where they breed. Of the 210 species recorded from the basin, 136 are widespread in the Afrotropics while 74 species appear to have limited distributions.
• There are about 1,100 species of butterflies recorded from the Zambezi Basin. The richest area is again the headwaters of the Zambezi around Mwinilunga, where 340 species have been recorded.

Freshwater molluscs have been comparatively well studied across the basin as some species are intermediate hosts of the parasite, which causes schistosomiasis or bilharzia. Of the 98 indigenous species recorded from the basin, 47 are found in Lake Malawi/Nyasa. Of the 98 species, 28 are endemic to the basin, including 23 endemic to Lake Malawi/Nyasa, showing the biodiversity importance of this unique lake.

The economic importance of wildlife is obvious - it provides meat in many areas and can be a major draw for tourism in others. Birds of economic significance include ducks and geese, many of which are hunted for meat. Some wetland areas of the basin, such as the Kafue Flats, have great concentrations. Francolins and guinea fowl are also hunted for food in many areas.

Economically, fish are of major importance in areas close to reservoirs and along major rivers. The Lake Tanganyika sardine, or kapenta, was introduced into Lake Kariba in the late 1960s, and more recently into Cahora Bassa. It now forms the basis for an enormous commercial fishing industry. Some 17,034 tonnes of kapenta were, for example, harvested in 1997 on the Zimbabwean side of Lake Kariba alone compared to 1,172 tonnes caught in 1977.

Reptiles of economic importance include turtles and crocodiles. The raising of the Nile crocodile is now a commercial enterprise in the Zambezi Valley, with eggs often being collected from the wild and a number of one- or two-year-old infants being returned to maintain populations in the wild.

Threats to biodiversity

The major changes in biodiversity have resulted from land clearance and from overexploitation of certain species of economic value, the construction of large and medium-sized dams along the Zambezi River and its catchment. Pollution and fire are other threats to biodiversity in the Zambezi Basin.

Land is still being cleared for agriculture, particularly in what were marginal agricultural areas in the Middle Zambezi Valley, and also for increasing urban populations in Zambia and Zimbabwe. In Zambia, for example, the World Bank estimates that the conversion from forest to cultivation is expected to increase by 1.5 percent annually.

The introduction of alien organisms is a major concern to conservationists. Some alien species can out-compete native species or modify the ecology of an area. Examples include the invasion of pines and wattle trees into the montane grasslands of Mount Mulanje in Malawi and Nyanga in Zimbabwe and, the introduction of the Nile Tilapia fish into the waters of the Middle Zambezi, and Kariba weed into the Chobe system and Lake Kariba. The introduction of the Lake Tanganyika sardine into Lake Kariba in the 1960s has not resulted in loss of biodiversity as a new habitat was created and there were no native species to occupy it. However, fears have been expressed over the possible introduction of kapenta into Lake Malawi/Nyasa where it would feed on lake flies, which are the main food for some endemic cichlids, endangering these species.

Fire has modified vegetation structure and species composition in the moister woodlands with a good grass layer, and in particular in the extensive grasslands associated with floodplains. Large areas of Barotseland are burnt regularly, as are the grasslands of the Zambezi Delta. Soil erosion is increased, and plant and animal species, which cannot avoid fire, by flying away, going underground, or regenerating rapidly, are reduced in distribution and abundance.

Increasing use of fertilisers in agriculture and large urban populations discharging large volumes of sewage, have given rise to acute problems of water pollution, such as in Lake Chivero outside Harare. The use of DDT against tsetse fly in the Zambezi Valley in Zimbabwe has negatively affected birds.

As a result of land clearance and other factors, some species such as the blue wildebeest in Malawi, the tssessebe in Mozambique and the kob in Tanzania have become extinct, and others face high risk of extinction in the future. Species facing high risk of extinction include, for example, birds such as the Wattled Crane and mammals such as the African Wild Dog or Painted Hunting Dog, the Kafue Lechwe and the Black Rhino.

Biodiversity management

Although some African countries signed environmental policy instruments or multilateral environmental agreements (MEAs), enforcement remains a problem due to constraints such as:

• Inadequate policy framework for implementation.
• Constraints of financial resources.
• Lack of qualified personnel in the different disciplines related to MEAs at the national level.
• Inadequate participation by national stakeholders as well as the general public, in the negotiations of MEAs.
• Failure of some MEAs to reflect national environmental priorities.
• General absence of in-depth understanding of the contents of MEAs.

Wildlife management has traditionally been top-down with the state owning the wildlife in protected areas and enforcing wildlife legislation through state agencies. However, a number of innovative responses to the weaknesses in wildlife management have been introduced. These include game ranching, which allows ownership of wildlife to be transferred from the state to the individual ranchers.

Another innovative response to the dwindling wildlife resource has been the introduction in the 1980s, of community-based natural resource management (CBNRM) programmes. CBNRM programmes seek to enhance conservation of biodiversity outside protected areas and private lands while at the same time affording rural people benefits from the wildlife resources in their areas.

One of the major constraints in the development of sustainable forestry management is that information regarding appropriate forest management systems for the various indigenous forest types is lacking in most of the basin states. This is partly attributed to past national forestry policies which gave higher priority to the establishment, management and protection of exotic softwood and hardwood forest plantations than to the indigenous forests.

Future challenges

Although studies of the classification of living organisms (taxonomy) has named and classified many of the organisms found in the basin, this knowledge is not evenly distributed across the different biological groups. For example, over 95 percent of flowering plant species present have probably been named, but less than 50 percent of the beetles. Consequently, reasonable statements can be made on the biodiversity of groups such as flowering plants, mammals, birds and fish, but it is very unclear on total diversity and patterns in groups such as bacteria, beetles and other invertebrates.

The biodiversity of the basin as a whole has not been comprehensively documented. Studies have been concerned principally with individual groups or with individual countries rather than the whole basin.

There is, therefore, a need for commitment by the governments of the region to implement and sustain integrated, multiple land-use management policies with rural people in order to realise the full benefits of flora- and fauna- resources.

Top