Plant Responses to Drought and Climate Change in the Southwestern United States

Science Center Objects

Land managers face tremendous challenges in the future as drought and climate change alter the abundance, distribution, and interactions of plant species. These challenges will be especially daunting in the southwestern US, which is already experiencing elevated temperatures and prolonged droughts, resulting in reduced soil moisture in an already water-limited environment.  These changes will negatively affect plant growth and may result in shifts of plant community composition and ecosystem function. The broad-scale effects of climate change and complex spatial heterogeneity of abiotic and biotic conditions across the southwestern U.S. makes it difficult to use site-specific data to assess climate-plant relationships. We are conducting regional cross-site analysis to identify at risk plant species, functional types, and plant communities that can help managers mitigate and adapt to shifts in plant community composition, distinguish changes due to climate versus land use, and construct future conservation policies.        

Background & Importance

Map of 2000 and 2010 perennial vegetation cover (left insets), and change in perennial vegetation cover between 2000 and 2010
Map of 2000 and 2010 perennial vegetation cover (left insets), and change in perennial vegetation cover between 2000 and 2010 following a period of extended drought. Abbreviations: DEVA = Death Valley National Park; JOTR = Joshua Tree National Park; MOJA = Mojave National Preserve. CLICK ON IMAGE TO ENLARGE IT. (Credit: Seth Munson, USGS. Public domain.)

Recent elevated temperatures and prolonged droughts in many already water-limited regions

throughout the world, including the southwestern United States, are likely to intensify according to future climate-model projections. This warming and drying can negatively affect perennial vegetation and lead to the degradation of ecosystem properties. To make accurate predictions of plant responses to climate change, it is valuable to determine the long-term dynamics of plant species associated with historical conditions.

General Methods

For this research, we are determining how plant species and functional types across a wide range of ecosystems in the southwestern U.S. have changed with drought and elevated temperatures to inform predictions of future plant species assemblages. We are using a fusion of ground-based monitoring and remote sensing to assess plant responses. Because soils, landform, and geology have a strong influence on water-availability in this region, we are integrating these environmental characteristics to examine how they moderate climate-vegetation relationships at local to regional scales.

Important Results

We have completed analyses for the Colorado Plateau, Sonoran, Chihuahuan, and Mojave Deserts. Results indicate the plant species and communities that are most vulnerable to climate change, and where on the landscape they are most susceptible. These results are being used to help land managers anticipate and prepare for reductions in water availability.

Future Directions

Future work involves: 1) comparing the long-term effects of climate with land-use, 2) coupling historical results with simulation modeling to predict future changes, and 3) understanding how climate-induced plant responses affect ecosystem function (e.g., soil erosion, carbon storage, and wildlife habitat).