Climate change projections for Southwest vegetation change

Recent and rapid mortality in southwestern United States forests has prompted concern among ecosystem managers regarding the effects of future climate changes on vegetation. Managers seek guidance regarding the composition of ecosystems and species responses to temperature and moisture changes. This presentation synthesizes information garnered from two efforts: (a) ecosystem manager comments from a series of workshops devoted to climate variability and change in Southwest ecosystems, and (b) downscaling climate projections to spatial scales useful for assessing potential changes in the range of individual plant species. The kinds of climate tools that will help managers, based on examples from the desert Southwest, include (a) regional climate change monitoring and data management working groups that address standards for monitoring project design and data management, (b) climate education, including information sharing, professional development, and capacity building to use climate variability and change information in decision-making, and (c) data and visualization tools that link instrumental climate data with climate change projections, vegetation change projections, and management scenario options. Downscaling climate change projections for use by modelers and managers in the Southwest is constrained by instrumental calibration data challenges, such as estimating spatial precipitation variability in highly varied terrain, and the accuracy and reliability of GCMs in portraying the strong seasonality of precipitation. Results from a statistical downscaling study indicate that very few models can reasonably simulate precipitation seasonality for the southern Colorado Plateau, which is critical for estimating vegetation habitat requirements; thus, an array of approaches, aside from ensemble averages, may be required as input for species-specific vegetation models.