Abstract

International Union for Conservation of Nature (IUCN) Red List assessments, which document the risk of extinction for a wide range of taxa across the globe, are a key component of conservation planning. Characterising the geographic range of species is central to Red List assessments. Ranges have traditionally been quantified by either drawing polygons around the georeferenced specimen locations (extent of occurrence, EOO ) or by summing up the coarse pixels in which the species are known to occur (area of occupancy, AOO ). Models predicting current and future patterns in the geographic range of species (species distribution models, SDMs) are now widely used in ecological and conservation research, but the utility of SDMs for informing Red List assessments is virtually unexplored. We therefore compared range measures derived from SDMs (based on threshold probabilities of occurrence) to IUCN -accepted range measures based on field observations of the locations of 30 species occurring in Costa Rica and Panama. We find that SDMs often predict similar ranges to those estimated by standard EOO methods, but give very different results to those obtained by AOO methods. The benefits of using SDMs in assessing species’ geographic range for Red List assessments are that the map predictions help identify whether there are unexplored areas that may potentially be part of a species’ range.