Sustainable resource management requires understanding the factors that increase or decrease species richness. Regional species richness patterns may be predicted by analysing patterns of variation in the environment. A number of studies have shown that bird species richness at a regional scale is influenced by climatic variables. We examined environmental correlates of bird species richness at a quarter degree square scale (55 × 55 km). Mean annual potential evapotranspiration accounts for 46% of the observed variation in species richness, while mean annual temperature and range annual potential evapotranspiration are significantly correlated with species richness and together account for a further 5% of the observed variation. The results are consistent with the hypothesis that environmentally available energy limits regional species richness.
- energy theory