Background/Question/Methods
The impact of 21st century climate change on the diverse ecosystems of the Southwest United States is investigated. The Lund-Potsdam-Jena dynamic global vegetation model (LPJ-DGVM) is forced with 21st climate projections from 17 general circulation models within the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4). Additional simulations isolate the individual impacts of changes in temperature, precipitation, and carbon dioxide. 

Results/Conclusions
Results generally indicate a substantial loss of vegetation, including Rocky Mountain evergreen forests and semi-arid grasslands, and an enhancement of fire activity. To better understand the changes in plant functional types simulated by the LPJ model, the modern and future climate envelopes for 170 tree, shrub, or cacti species in the Southwest is determined based on the range of nine climate variables specificed for each plant in the Thompson et al. atlases. Significant shifts in plant climate envelopes are predicted, at times faster than plant migration can occur.