The introduction of domestic livestock to the Kalahari has been accompanied by significant changes in the rangeland ecology, reflected most obviously in a shift from herbaceous to woody plant species. The exact mechanisms behind this are still unclear, and it remains uncertain whether the vegetation changes are a direct response to increased grazing pressure, or whether they reflect more fundamental changes in ecosystem function.
Despite this uncertainty, it is common in the literature to see bush encroachment’ used interchangeably with the more general terms land degradation; and desertification. Whether or not this usage is always intentional, it is almost certainly misleading. Most recent definitions of land degradation (e.g. UNEP 1992) suggest that degradation is the result of irreversible changes, reflecting loss of ecosystem resilience. The use of forage quality as a single surrogate for land degradation is therefore questionable. On their own vegetation changes are poor indicators of damage to resilience (indeed many see the co-adaptation of vegetative communities and land use as evidence that resilience is intact), although in Botswana they are usually assumed to be symptomatic of loss of resilience.
In reality resilience is seldom at stake unless the vegetation changes are accompanied by soil degradation. In this paper we explore the links between grazing, ecological change and land degradation for a heavily grazed area of the Kalahari. In particular, we examine the relationship between ecological conditions and soil properties and processes. The results are striking. Data for soil nutrient dynamics and soil water redistribution show that basic soil processes are relatively unaffected by grazing pressure, with ungrazed and heavily grazed sites showing essentially similar characteristics. Certainly there is no evidence to suggest grazing leads to soil degradation, and as such links between cattle and land degradation’ should treated with care.