A study of the major components of the Kalahari Pan ecosystem

Abstract

Scattered throughout the Kalahari sandveld of Southern Africa are saucer-shaped depressions known as pans or salt-pans, which vary in size from less than 30 m in diameter to as much as 5 km in diameter. A cross-section of these pans in the Mabua Sehube and Khutse Game Reserves in Botswana were studied from 1968 to 1972 as part of the overall wildlife research program in Botswana. The study included regular animal counts, pellet counts, measurements of vegetation and vegetation use, and determination of soil properties. Pans were shown to be heterogeneous habitats in a relatively homogeneous sandveld environment which support a characteristic vegetation with many Karroid features. They were also shown to be focal points for many wildlife species and are the sites of important wildlife salt-licks and seasonal water-holes which are not found in the sandveld. Human activity in the Kalahari was found to be largely concentrated around pans, although the recent drilling of boreholes is altering the pattern of human distribution. The study further demonstrated how these valuable pan habitats or ecosystems are actively maintained by the combined interaction of their various biotic and abiotic components. An example of this interaction is that run-off water concentrates soluble minerals and fine soil particles, which form the basis of the salt-licks and water-holes, in the lower parts of the pan. The salt-licks and water-holes attract animals and animal use results in a removal of soil from these areas, which helps to maintain their depth and so ensure that further run-off water flows into them, thus completing the cycle. Other factors including herbivore pressure on the vegetation and wind erosion were also shown to play a role in maintaining the pan ecosystem. The study underlines the need to conserve and understand ecosystems rather than individual species or groups of species, and it is hoped that these results will contribute to a better understanding of the Kalahari and so assist in its conservation.