Succulent takeover

When shallow shale or mudstone soil is washed away from an arid Little Karoo slope, habitat loss may cause surface rock to become exposed. This results from drought or too high browser and grazer population density. It may happen quickly, over extended periods or may have happened long ago.

Semi-arid land is delicate, easily disturbed by damage from overuse. Carrying capacity is a function of variable conditions, exceeding it not always easy to recognise timeously. Stressed vegetation during drought and trampling by hungry animals cause topsoil to loosen, blow away in the wind or run off from heavy seasonal inundation. Concomitant plant and species losses may be huge, even over a comparatively short period.

The vegetation is here reduced to Crassula rupestris, Portulacaria afra and not too much else. The few resilient species take up space previously occupied by a multitude of others, less robust in trying times. Once such erosive processes have taken over, they are not easily stopped, let alone turned around. This is so even when veld is allowed to rest without game or livestock for long periods.

Soil loses physical, chemical and biological properties once the strong vegetation of a diverse ecology disappears; a situation not easily retrieved (Vlok and Schutte-Vlok, 2010; Fuggle and Rabie (Editors), 1983).