The Great Lakes Belt of Africa cuts across five major drainage basins: The Nile, Congo-Zaire, Rift Valley, Coastal and Zambezi basins. The region contains the earth's largest aggregation of tropical lakes. Three of these lakes–Victoria, Tanganyika and Malawi—hold one quarter of the earth's total surface water supply, and are home to rich and diverse assemblages of fish. Apart from the diversity and endemicity of their biota, properties that distinguish the African Great Lakes from their North American counterparts include their great age, sensitivity to climate change, long residence times, persistent stratification, continuously warm temperatures at all depths, major ion composition, and propensity for nitrogen limitation. Current management problems include over-fishing, increased input of sediment and nutrients, and in the case of Lake Victoria, loss of endemic fish species and the proliferation of the introduced water hyacinth. The harmonization of research programmes and management strategies among the various riparian countries is a challenge. Among the other challenges currently facing the African Great Lakes, perhaps none is more important, nor more often overlooked, than the ecosystem-based management. Ecosystem integrity is beginning to receive acknowledgement in some quarters as a foundation upon which sound management must be built. Recent changes in the African Great Lakes have resulted in an increased realization that individual components of these systems cannot be understood in isolation, and that effective management must expand beyond conventional fisheries management to account for the interaction of physical, geological, chemical and biological processes at the ecosystem scale. Although specific processes in tropical aquatic ecosystems, such as hydrodynamics, plankton production and fisheries production have received some attention, there remains a need to integrate these processes in order to gain a better understanding of ecosystem functioning. One means of achieving this is through the development of conceptual and numerical models, which can facilitate both the theoretical understanding and applied management of these ecosystems. As management problems move from the relatively simple issue of fishery control to the more complex issues of climate change and land use, models will play an important role in decision-making processes regarding sustainable utilization of these vital natural systems.
Keywords biophysical aspects, natural and anthropogenic pressures, policy applications