Biodiversity representation in Uganda's forest IBAs

Prioritising sites for action is essential due to current rates of population and habitat loss and increasing human numbers and demands on natural resources. Many prioritisation methods have been suggested at different spatial scales, including those based on single-taxon criteria. One such scheme is BirdLife International's system of important bird areas (IBAs). Whilst IBA site qualification criteria are entirely bird-based, the intention is that these sites should conserve wider biodiversity. This idea has yet to be tested quantitatively, but a unique opportunity to do so exists in Uganda, where the Forest Department (FD) has conducted comprehensive inventories of five taxa (birds, butterflies, large moths, small mammals and woody plants) in 50 Ugandan Forest Reserves. Independently, Nature Uganda (the national conservation NGO) identified 30 IBAs, 13 of which were also forest reserves. In this paper we used the FD dataset to evaluate the efficiency with which Uganda's forest IBAs capture species richness in other groups. In a combined area of 5445 km2, Uganda's 13 forest IBAs contained as many species as did an equal-sized set of sites selected by applying a complementarity-based algorithm to all FD data. Modifying this simple greedy algorithm to take account of site area resulted in a priority set that outperformed IBAs, but that consisted of far more sites for similar species representation. Our results illustrate the utility of the IBA network for representing a wide range of biodiversity. A major benefit of IBAs is the low cost of obtaining bird data relative to comprehensive multi-taxon inventories. The general applicability of these results outside tropical forests requires further investigation.