Effects of artificial water points on the Oshana ecosystem in Namibia

Abstract

In the semi-arid rangelands of the Oshana ecosystem in Northern Namibia, there are general concerns that artificial water points for domestic use contribute to the processes that lead to desertification. The processes begin in piospheres of artificial water points. Among the processes suggested to correlate with radial distance and age of water points are loss of perennial grass species, an increase in annuals, and general loss of herbaceous species richness, herbaceous biomass and grass cover, as well as an increase in forb cover and in bare ground and litter cover. Radial distance and age of artificial water points impacts were compared using these indicators with benchmarks in saline grassland and mopane landscape at the end of the wet season. Radial distance influenced herbaceous species richness, grass cover and bare ground, while the variability of the perennial:annual grass ratio, herbaceous biomass, forb and litter cover were attributed to differences between landscape types. Age of water points influenced only herbaceous species richness, while forb cover was associated more with water points than benchmarks. Forb cover was sporadic in relation to age of water points. In the Oshana ecosystem, therefore, radial-grazing distance could not be used to explain changes in the perennial:annual grass ratio. Many of the changes were explained by differences between landscape types. The mopane landscape was more vulnerable to degradation induced by artificial water points than the grassland landscape. The implication is that, in the future, greater care should be taken to space water points in the mopane landscape.