Bird species richness and densities in relation to sulphur dioxide gradients and environmental variables

The expansion of coal-fired power stations in South Africa has resulted in growing environmental concerns as they are the largest emitters of sulphur dioxide (SO2). Sulphur dioxide emissions from power plants pose a potential threat to avian populations. However, the effect of SO2 pollution on bird communities is poorly understood. Using point counts we investigated the relationships of bird species richness and species-specific density with SO2 concentrations around Matimba power station. Environmental parameters were derived from remotely sensed data and data reduction was performed using principal component analysis. Generalised linear mixed models were then used to infer the relationships of bird species richness and species-specific densities with SO2 concentrations and the environmental variables. Our results revealed that SO2-polluted air had no influence on bird species richness and densities in our study sites, but SO2 levels were below annual national ambient air quality standards. Vegetation productivity was found to have a greater influence on species densities than SO2 pollution. Monitoring of bird population changes around Matimba power station once neighbouring Medupi power station is fully operational is recommended, as SO2 content of the air will increase significantly, and species may be sensitive to this increase in SO2 levels.