Get reliable science

The numbers of livestock and wildlife that can be supported in an arid environment such as the Hoanib River catchment, north-western Namibia, are determined by annual and seasonal availability of grazing and browsing. The availability and abundance of vegetation was investigated in eight focus-study areas across the catchment. The vegetation of the focus area was observed to behave in a non-equilibrial manner in that it was dependent on annual rainfall rather than intensity of landuse. The Zurich-Montpellier method of vegetation assessment was used for the evaluation of vegetation plots. The amount of dry season grazing was also dependent on the previous season's rainfall, with [`]dead grass' and perennial grass only available after an [`]above average' rainfall season. Vegetation communities were dominated by mixedColosphosermum mopane woodlands in the 100-350 mm rainfall zone, while perennial grasses dominated the 50-100 mm rainfall zone. While the bulk rangeland appeared not to be disturbed by landuse, a 2 km [`]sacrifice zone' around water sources was found to have changes in vegetation species and abundance. During below-average rainfall seasons and drought, when there is limited or no grazing, browse becomes the most important source of nutrition for domestic stock and wildlife.