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 created through evolution taking place in environments which became isolated from each other. The lakes also provide an outstanding example of the loss of biodiversity: in Lake Victoria at least 200 species of fish have almost certainly become extinct through human activities. These lakes have, since Mankind's origin in Africa, provided high-quality animal protein food and with improved management they could provide much 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. Barriers to the movements of fish were thus created. The discussion moves to the degree of biodiversity through evolution in situ and to the many scientific problems associated therewith. Finally comes the effect of human interference with Nature: native fisheries which had been developed using local materials were disturbed, sometimes by over-fishing, sometimes by creating new Man-made lakes, sometimes by introducing alien species of fish. In at least one case this interference with Nature has resulted in turning biodiversity on its head; but it is still arguable whether this introduction was of economic advantage or overall disaster. Ecological and fisheries' study of the African lakes has accelerated in recent years, with groups of research workers visiting from countries outside Africa. Three lakes which have been studied more than others, namely Victoria, Malawi, and Tanganyika, are considered in more detail than the rest. Every lake, whether natural or Man-made, and even some of the smallest which now occupy extinct volcanic craters, illustrate a measure of how new species come into being. In spite of a big accumulation of research on these lakes in recent years, many of the problems, including changes caused by pollution and the introduction of alien species, still await further and deeper study.