干旱区生态环境知识资源中心

Vegetation data collected around 8 piospheres in the southern Kalahari of Botswana show livestock impacts on vegetation cover and composition to be of limited spatial extent around the watering point. Dune crests can become active up to a distance of 1.2 km from the borehole with the latter sitting within an area of bare ground and a spectacular cauldron of active dunes some 50-200 m out. Data from an abandoned borehole show that the bare ground zone or "sacrifice zone" does recover, albeit with forbs and annuals, which serve to stabilise the formerly active dunes. Greater concern over the impact of piospheres lies beyond the sacrifice zone to the effects livestock keeping has had upon the resilience of the Kalahari ecosystem and the creation of large tracts of "empty Savannah". Livestock expansion has acted to block migratory corridors that link the protected areas and in turn trigger largely reactive wildlife management measures. These include fencing and Artificial Waterpoint Provision in an attempt to redress spiralling human wildlife conflict and the isolation of wild ungulates from historical sources of surface water, particularly in a drought. Successive aerial surveys of Kalahari ungulates show the failure of migratory ungulates such as blue wildebeest and red hartebeest to recover from the drastic die-offs that occurred in the 1980s drought. The need to manage the Kalahari ecosystem as a whole to ensure coexistence between domestic and wild ungulate populations and a greater diversity of livelihood opportunities to the benefit of impoverished rural communities is emphasised.