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refugia—sites that would have escaped the dramatic environmental changes that took place during repeated ice ages. They are not only sites of species richness and endemism but are also the habitat islands of rare and threatened species. Of the 168 species listed in Threatened Birds of Africa and Related Islands, the ICBP/IUCN Red Data Book, 87 are forest species (Collar and Stuart, 1985).
Many of these birds occur as isolated populations in widely separated montane forests. The most critically threatened group of these rare birds survive in the small patches of forest on Mount Moco in central Angola, more than 2,500 kilometers distant from similar but much larger forests in Cameroon, eastern Zaire, Tanzania, and the South African escarpment (Huntley, 1974). Pressure for timber and fuelwood on this 100-hectare remnant is severe—the rural peoples living on the cold mountain slopes have no alternative resources.
The Great Lakes of Africa are the only massive freshwater bodies in the tropics. They are comparable in size to the North American Great Lakes but are much older. The African lakes harbor the world’s richest palustrine fish faunas, one family of which (Cichlidae) provides the supreme example of vertebrate evolution within geographically isolated communities—upwards of 900 species—far more spectacular than that described and immortalized by Darwin in the 13 species of Galapagos finches.
Table 29–3 indicates the levels of species richness and endemism in the three largest African lakes. There are probably more than 1,100 species of indigenous fishes in these lakes, compared with less than 160 species in the much larger North American lakes. Not only are these fishes of immense ecological, evolutionary, and conservation interest, they also support a major traditional fishery. This fishing culture, and its socioeconomic fabric, is now being threatened by the introduction of sophisticated and capital-intensive fisheries based on Nile perch, an introduced species (Coulter et al., 1986). This piscivorous species was introduced into the northern part of Lake Victoria in 1960 in a well-intentioned but shortsighted effort to improve the commercial fishing industry. It has rapidly expanded its range in the lake at the expense of the endemic species. Massive changes in the abundance and distribution of these endemics are occurring, and it is estimated that up to 30 species have already become extinct. This is probably the highest rate of human-induced extinction of vertebrates yet recorded. The tragedy of the situation is that a vast number of the species currently threatened with extinction have not yet been collected, classified, and named.
TABLE 29–3 The Great Lakes of Africa: Area, Fish Species Richness, and Endemisma