Title: Climate Change in the Southwest - Potential Impacts (U.S. National Park Service)
Headings: Climate Change in the Southwest - Potential Impacts
Series: Climate Change in the Southwest
Climate Change in the Southwest - Potential Impacts
Climate change in the Southwest
Potential climate change impacts
Water
Vegetation
Vegetation shifts
Fire
Impacts by Region

Content: For example, at a site in the Chihuahuan Desert in southeastern Arizona, increases in winter precipitation correlated with shrub expansion into grasslands (Brown et al. 1997). Future changes in the seasonality of precipitation can be expected to alter the composition of plant communities. Warming, regardless of precipitation changes, can also affect plant communities. In montane ecosystems, warming is expected to cause plant species to shift upwards in elevation. In southern California, this shift is already happening. Between 1977 and 2007, dominant plant species in the Santa Rosa Mountains shifted upwards in elevation by about 65 m (Kelly and Goulden 2008). Warming may also affect the distribution of desert plants because of their sensitivity to freezing. Since the lower boundary of the Sonoran desert may be where freezes never happen and the upper boundary may be where freezes last less than 24 hours, warming temperatures would allow thorny shrubs and scrub trees from further south to establish in the current boundaries of the Sonoran desert, and the Sonoran desert would expand northward, eastward, and upward in elevation (Weiss and Overpeck 2005). From 1960 to 2000, the number of days below freezing has already decreased (Weiss and Overpeck 2005).