Effects of fencing on forage biomass and quality through livestock exclusion from a protected area in the southern Kalahari

Abstract

The substitution of wild herbivores by livestock has led to substantial degradation of many southern African grazing systems. As a result, bush and shrub encroachment has led to a reduction of grasslands, invasion of thorn shrubs, reduced carrying capacity of range land, and desertification. These changes often raise socio-economic challenges for rural communities in arid and semi-arid regions, as previously profitable areas may become no longer economically viable. This study aims to compare biomass and key chemical characteristics of grassy vegetation between sites experiencing low vs. high grazing pressures. Furthermore, we estimate the recovery time needed for pasture in heavily grazed areas to reach properties of similar sites under low grazing pressure. In heavily grazed areas, grass was of higher quality than in areas with low grazing pressure, as the remaining or re-growing grass contains higher percentages of protein and lower concentrations of fiber. However, as heavy grazing led to reduced grass biomass, the absolute amount of protein available per unit area was lower in areas with high compared to areas with low grazing pressure. Furthermore, at the heavily grazed area we recorded a high proportion of unpalatable plant species. The exclusion of livestock through fencing resulted in a rapid increase of grass biomass and therefore higher amounts of fibre, protein and hemicellulose contents per unit area after one wet season, whereas the chemical concentrations of plant compounds changed remarkably little after elimination of livestock grazing pressure.
In areas where cattle substitute wild-ranging herbivores we recommend livestock managers consider transitioning to sustainable grazing systems through grazing rotation, diversification of herbivore species, and reduction in stocking rates. This would secure sustainable livestock-based livelihoods while avoiding permanent rangeland degradation due to bush encroachment and desertification.