Global Climate Change Impacts in the United States 2009 Report Legacy site

Historically, distributions of plants and animals have shifted with changes in regional and global temperatures. Current predictions from general circulation models show changes in level and variation in temperature and rainfall over the next several decades. The magnitude and direction of such changes vary regionally. Studies are beginning to show that these changes will impact distribution of species of plants and animals., and, concomitantly, species composition of plant and animal communities. We used geographic information systems, vegetation models. and general circulation models to predict the impact of global climate change (GCC) on the distribution of vegetation at a regional scale, the state of Texas. Then we used habitat preferences for species of rodents in the state to predict how GCC would impact their geographic range and species richness. Our determination of suitable habitats for species of rodents included an average of 98% of capture points, and we found that suitable habitat averaged 62% of the geographic range of species. Size of habitat-corrected range increased an average of 2- to 3-fold under GCC, indicating that rodents were more adaptable to changes in vegetation than were other mammals we studied (e.g., lagomorphs and insectivores), whose range decreased, but similar to Chiroptera. whose ranges also increased. Geographic ranges shifted an average of 54% under a warmer, wetter climate and 61% under a warmer, drier climate, resulting in inclusion of an average of 60% new vegetation associations in the ranges under the former scenario and 64% under the latter scenario. The impact of GCC on rodents in Texas was greatest under the warmer, drier climatic scenario. Two species, Oryzomys cousei and Microtus mexicanus, were predicted to go extinct because their suitable habitats did not occur under GCC. These results demonstrated that the type of climate change (warmer, drier or warmer, wetter) and its severity would be important. GCC was predicted to have the greatest impact on rodent distributions in eastern Texas under a scenario of a warmer and wetter climate because forests expanded, whereas the impact would be greatest in western and southern Texas if climate becomes warmer and drier because desert and shrub habitats expanded. Life-history variables (e.g., habitat type or diet) were correlated with changes in size of range, location, or habitat composition, and reflected broad changes in the relative distribution of vegetation types. Granivores and herbivores used fewer new habitat associations that entered Texas after GCC than did omnivores or insectivores, as did terrestrial rodents compared with fossorial or arboreal rodents.