Modelling individual and collective species responses to climate change within Small Island States

Very little empirical work has been done to assess the potential impacts of climate change upon terrestrial biodiversity within small islands, many of which contribute to global species diversity due to high levels of endemicity. This study illustrates projections of not only individual but also the 'collective' response of a group of high conservation value tree species to climate change within the Caribbean small island of Trinidad. The species distribution modelling algorithm MaxEnt was used to construct models of the realised present environmental space occupied by these species based on present day climate and other environmental factors. These models were then used to estimate present and future (2050; SRES A2) distributions of these species across Trinidad. Both present and future model output were incorporated to create change maps which illustrate projected expansions, contractions and areas of stable environmental space for each species. Individual change maps were combined to create a 'collective' change map portraying projected changes in the environmental space of this species group as a whole. Most individual species and the collective group response were projected to lose more than 50% of present environmental space, with the latter being limited to the southern edge of the island. Our results suggest that small islands may experience an eventual disappearance of endemics and other valuable species under SRES A2 conditions, which may serve to further depreciate global terrestrial species diversity. Application of this 'collective' response may be particularly useful for planning within the limited geographic spaces available for conservation within small islands.