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![]() The lakes and rivers of Africa's Rift Valley comprise some of the most diverse and important natural freshwater ecosystems on the continent. Ranging from a suite of shallow depressions and small lakes in the Ethiopian Highlands, to the second largest water body in Africa, the Rift Valley Lakes lie scattered across 10 countries. The Great Rift Valley, often referred to as the 'cradle of mankind' because of the many discoveries of early Man from the region, is one of the most striking features of the African landscape. Dotted along the length of the Rift, in tiny depressions and gigantic craters and crevices, are some of the continent's most important freshwater habitats. With an area of 32,893 square kilometres, Lake Tanganyika is the longest and second deepest lake in the world, and the second largest lake in Africa. The Rift Valley has long served as a passageway for people and nature. Animals and plants have always migrated along the valley, shaping the African landscape in a similar manner to the powerful geological forces which first created it. The rugged and scarred landscape of the valley led to the evolution of a multitude of habitats and species. In places, the valleyÕs unique ecological and climatic conditions contributed to the evolution of extraordinary levels of species diversity, particularly in the lakes and rivers of eastern Africa. More than half of the world's cichlid species (small freshwater fishes of the family Cichlidae allied to marine damselfish and wrasses) are found in the lakes of East and Central Africa. The freshwater resources of these lakes are an essential lifeline to millions of people who depend on the rich fisheries as their main, and often only, source of protein. Many of the lakes are ecologically unique and their unusual features have attracted the attention of scientists throughout the world since the end of the 19th century. A large number are isolated with no outlets, a situation which creates unusual ecological conditions.. Many water bodies, such as Lake Nakuru in Kenya, are shallow alkaline soda lakes which support massive growth of algae and zooplankton. Others have extremely high levels of salinity, conditions which favour growth of very different microscopic life forms compared with freshwater lakes. |