Boon, Randall B. 2005. "Quantifying Changes in Vegetation in Shrinking Grazing Areas in Africa." Conservation and Society 3(1).

Abstract

"Pastoralists around the globe are being sedentarised and livestock mobility is declining. Animals once able to move about landscapes to access ephemeral green forage are being confined to small areas with fewer forage choices. The ecosystem model SAVANNA was used to quantify the effects of land subdivision and sedentarisation on vegetation traits in South Africa and Kenya. In South Africa, significant declines in high palatability green leaf biomass, annual net primary productivity, and root biomass were recorded as a 300 km2 block of land was subdivided into parcels of 10 km2. In contrast, low palatability biomass measures generally increased. Woody plant populations and slow decomposing soil organic matter increased significantly, whereas surface litter declined. In southern Kajiado District, Kenya, group ranches in which livestock populations declined under subdivision showed increases in herbaceous biomass, whereas the ranch where livestock populations did not change under subdivision had less herbaceous biomass. Livestock within small parcels were food stressed in the dry season and their populations declined so that vegetation increased beyond what could be eaten in the wet season. The vegetation changes modelled led to, or reflected, significant declines in livestock. The results suggest that stakeholders should retain open access to subdivided lands to reduce loss of vegetation productivity."