Determining the extent and condition of riparian zones in drinking water supply catchments in Sarawak, Malaysia

Land cover within eight drinking water catchments in Sarawak was classified into six categories using satellite imagery and GIS. The categories represented varying levels of vegetation modification from largely undisturbed or mature secondary vegetation (Category 1) through to bare, non-vegetated areas (Category 6). Rivers less than ~10 m in width were usually ‘invisible’ on satellite images because of dense canopy cover. More than 70% of headwaters in all catchments, except one (Buri Bakong), were not visible, indicating the presence of dense riparian vegetation. For the river sections that were visible on satellite images, 5%–22% of the riparian buffer was highly degraded (completely lacking vegetation). The highest degree of riparian modification occurred in the lowlands, the midland catchment of Tingkas and the highland catchment of Trusan. Although Sarawak government policy requires buffer widths of 5–50 m of natural vegetation to be retained along all streams and rivers in drinking water supply catchments these guidelines were not met at nine of the eleven field sites surveyed. These results suggest that compliance with buffer guidelines is important to water quality in rivers, particularly in logging areas, oil palm plantations and near settlements

A positive relationship between ant biodiversity (Hymenoptera: Formicidae) and rate of scavenger-mediated nutrient redistribution along a disturbance gradient in a south-east Asian rain forest

Human modification of pristine habitats almost always leads to the local extinction of a subset of the species present. This means that the ecosystem processes carried out by the remaining species may change. It is well documented that particular species of ants carry out important ecosystem processes. However, while much work has been carried out to investigate the link between biodiversity and ecosystem functioning in other taxa, this has received relatively little atten-tion for ant communities. In particular, no attempt has been made to link levels of ant diversity with the rates of nutrient redistribution carried out by scavenging species. Here we investigate the impacts of anthropogenic disturbance on the rate of scavenger-mediated nutrient redistribution, using bait-removal rate as a surrogate measure. We found that although ant species richness, diversity, biomass and rates of bait removal did not change systematically across the disturbance gra-dient, the rate of bait removal was related to ant species richness. Sites with more ant species experienced a faster rate of bait removal. This is the first documented positive relationship between ant species richness and the rate of an ecosystem process. If these results are applicable at larger spatial scales for a wider range of nutrient sources, loss of ant species could lead to important changes in the way that ecosystems function