Stocking density and distribution in relation to vegetation in a biodiverse semi-arid pastoral system in South Africa

Abstract

The spatial heterogeneity of vegetation in a communal grazing system provides pastoralists with a range of grazing sites to select for their livestock. When fencing spatially constrains herds, there is reduced access to ecological heterogeneity, which may have a negative impact on livestock and the grazing resource. This study investigated temporal and spatial changes in stocking densities and distribution within the six major vegetation types of the Leliefontein pastoral area in Namaqualand, South Africa. This semi-arid, biodiverse area of about 2000 km2 supports a spatially-constrained mobile pastoral system based on small stock production. Over the data period from 1999 to 2006, the location of 256 small stock herds, their temporal occupancy and herd size were used to determine stocking densities within the daily grazing radius of herds. These grazing radii were overlaid using GIS to produce stocking density distributions over the landscape. The density and location of herds were unevenly distributed when assessed monthly and annually. Parts of the study area were consistently overstocked whereas others remained ungrazed. We argue that the recommendation of fixed stocking rates within this variable environment is inappropriate because forage availability and quality fluctuate within and between years and within drought cycles. We conclude that development interventions should rather focus on reducing stocking densities during and after drought periods. This would benefit pastoralists through reduced livestock mortalities and the vegetation would recover more quickly from the impacts of drought.