ECOLOGY AND MANAGEMENT OF LAKE NAIVASHA, KENYA, IN RELATION TO CLIMATIC-CHANGE, ALIEN SPECIES INTRODUCTIONS, AND AGRICULTURAL-DEVELOPMENT

Lake Naivasha is an important freshwater resource for Kenya's foreign-currency-earning agriculture and tourism, and for water-supply. It has always experienced extensive water-level fluctuations as a consequence of irregular rainfall patterns that are affected by continental-scale climatic events, and its communities - particularly of aquatic plants - were adapted to these changes. Introductions of the Crayfish Procambarus clarkii to the Lake, together with the accidental arrival of Coypu (Myocastor coypus) and the floating water-fern Salvinia molesta in the 1960s and 1970s, have combined to produce dramatic effects; the latest decade, during which the native aquatic flora was severely reduced, is just ending. A potentially serious threat is now posed by rapid agricultural expansion and swamp clearance during the present phase of declining Lake-levels - particularly as there is no overall management authority for the Lake. Four main steps are proposed towards developing sustaintainable management of the Lake for all its uses. The first is that a 'buffer' of natural vegetation be maintained around the Lake-margin. The second step is that an overall management plan be drawn up, paying attention to: (1) the balance between human water-use and maintenance of the Lake; (2) the balance between agriculture and wildlife conservation in the irrigated zone around the Lake; (3) the overall pattern of land-use within the Lake catchment; (4) the provision of an agricultural advice and incentives scheme to cover the above; and (5) continued careful management of the Lake fishery. The third step is that a full-time ecological and hydrological monitoring programme be implemented, to provide the accurate information necessary for implementation of the management plan. The fourth step is the establishment of an effective programme of education on environmental and water conservation needs and their scientific bases.