SPREADING DESERTS OR SPATIALLY CONFINED ENVIRONMENTAL IMPACTS - LAND DEGRADATION AND CATTLE RANCHING IN THE KALAHARI DESERT OF BOTSWANA

The Kalahari Desert of Botswana is being increasingly used for livestock production, particularly through the establishment of ranches dependent on borehole water supplies. Reports of the environmental impacts of land use practices in such drylands are conflicting, with livestock systems supplied by boreholes and wells being regarded in some studies as centres for the spread of desertification and in others as having environmental impacts that are overridden by the effects of natural climatic variability. The results of an environmental study focused on a block of borehole ranches established in the eastern Kalahari as part of Botswana's Tribal Grazing Lands Policy dating from the 1970s are reported. The investigations concentrated on ecological, soil chemistry and soil erosion impacts on the study ranches. Although important changes in the ecology and soil nutrient status of the ranches are identified, their contribution to environmental degradation must be viewed in terms of stocking levels, the radial nature of range usage, giving rise to marked spatial variations in impact, and natural climatic variability. Changes are not solely detrimental, but long-term monitoring, especially in relation to climatic fluctuations, needs to be undertaken to fully establish the dynamic interactions of variables.