AFRICAN LAKES REVIEWED - CREATION AND DESTRUCTION OF BIODIVERSITY

The lakes of Africa provide outstanding examples of biodiversity. Some hundreds of species of aquatic fauna, especially fishes, have been cr eated through evolution taking place in environments which became isol ated from each other. The lakes also provide an outstanding example of the loss of biodiversity: in Lake Victoria at least 200 species of fi sh have almost certainly become extinct through human activities. Thes e lakes have, since Mankind's origin in Africa, provided high-quality animal protein food and with improved management they could provide mu ch more, which adds greatly to their scientific and economic interest. The origins of the lakes, their isolation into groups and individual lakes, resulted from earth movements, climatic change, and erosion. Ba rriers to the movements of fish were thus created. The discussion move s to the degree of biodiversity through evolution in situ and to the m any scientific problems associated therewith. Finally comes the effect of human interference with Nature: native fisheries which had been de veloped using local materials were disturbed, sometimes by over-fishin g, sometimes by creating new Man-made lakes, sometimes by introducing alien species of fish. In at least one case this interference with Nat ure has resulted in turning biodiversity on its head; but it is still arguable whether this introduction was of economic advantage or overal l disaster.Ecological and fisheries' study of the African lakes has ac celerated in recent years, with groups of research workers visiting fr om countries outside Africa. Three lakes which have been studied more than others, namely Victoria, Malawi, and Tanganyika, are considered i n more detail than the rest. Every lake, whether natural or Man-made, and even some of the smallest which now occupy extinct volcanic crater s, illustrate a measure of how new species come into being. In spite o f a big accumulation of research on these lakes in recent years, many of the problems, including changes caused by pollution and the introdu ction of alien species, still await further and deeper study.