Problems and solutions to modelling species distributions at a global scale: the importance of taxonomic and specimen databases
Peter Brewer and Frank Bisby, Centre for Plant Diversity and Systematics, The University of Reading, Reading. RG6 6AS. United KingdomVarious methods for modelling the potential distribution of plants and animals have been developed over the last decade or more. However, the spatial resolutions at which these studies have been completed have been limited to local, regional and continental scales. During this research, attempts to model the global distribution of a number of plant species have successfully identified a number of key problems with scaling existing modelling approaches to a global perspective. Whilst the modelling algorithms themselves have no inherent problem modelling distributions at a global scale, there are difficulties associated with the specimen and climate data required to perform these predictions. Although there are an increasing number of specimen databases online they are almost exclusively limited in geographic extent. Specimen data must therefore be collated from multiple sources creating further problems associated with taxonomy. A firm grasp of a species taxonomic status is required to ensure all specimens of a particular species concept are retrieved. Additional problems are posed by the climatic datasets required by the bioclimatic modelling algorithms. Whilst monthly climate data can be used in regional modelling studies, climate data must be pre-processed in global studies to ensure seasonal offsets between hemispheres are accounted for. Methods for overcoming all these hurdles are proposed and the importance of Global Species Databases (GSDs) in global distribution modelling is discussed.