Long-term studies of land degradation in the Sneeuberg uplands, eastern Karoo, South Africa: a synthesis

For the past 15 yr, the Sneeuberg uplands in the eastern Karoo, South Africa, have been a focus for research on land degradation by the above authors and other colleagues. Earlier work in the Karoo emphasised vegetation change whereas we concentrate on physical changes to the landscape at the small catchment scale, e.g., bare, degraded areas (badlands) and gully (donga) systems. Analysis of sedimentation in farm dams allows for reconstruction of environmental histories using 210Pb, 137Cs, geochemical and mineral magnetic properties of the sediments. Erosion rates on badlands are monitored using arrays of erosion pins. Sediment source tracing within small catchments points to the importance of hillslope sources and the relative erosional inactivity of gully systems. Sediment supply from hillslope and colluvial sources is maintained by high rates of weathering on mudstones and sandstones. Current degradation should be viewed in the context of a c. 200 yr history of overgrazing by European-style stock farming and limited areas of former cultivation in the valleys. Grazing pressures are now much reduced but the loss of soils and vegetation suggests that landscape recovery will require several decades. Additional drivers of past degradation are likely to have been periods of drought and fire(natural and managed) and a gradual increase in both rainfall intensity and the frequency of extreme rainfall events. The future of the degraded Sneeuberg landscape will depend on future farming practices. Desirable options include more sustainable livestock practices, adoption of wildlife farming and other more benign regimes involving mixes of agriculture, tourism, and wildlife protection together with landscape rehabilitation measures.