Modelling Climate Change Effects On Runoff and Soil Erosion In Southeastern Arizona Rangelands and Implications for Mitigation with Rangeland Conservation Practices.

Climate change is expected to impact soil erosion on rangelands in southwestern United States. This study was to evaluate the potential impacts of climate change on soil erosion and surface runoff in southeastern Arizona using seven GCM models with three emission scenarios for the 2050s and 2090s. A spatial- temporal downscaling process was used to generate daily precipitation series from GCM outputs for runoff and erosion modeling with the Rangeland Hydrology and Erosion Model (RHEM). Changes were compared to 1970 through 1999 conditions. Our results suggested no changes in annual precipitation across the region under the three scenarios, while projected annual runoff and soil loss increased significantly, ranging from 78.7% to 91.7% and from 127.3% to 157.1%, respectively, relative to 1970-1999. At the seasonal scale, though an increase of summer precipitation and a reduction of winter precipitation were projected, both runoff and soil loss increased significantly in the future.  The dramatic increases in runoff and soil loss were attributed to the increase in the frequency and intensity of extreme events in the study area.   Predicted soil loss on shrublands increases more than that for other plant communities under the three scenarios.  Future increasing runoff and soil erosion may accelerate the transitions of grassland to shrublands or to more eroded states due to the positive vegetation-erosion feedback. The option of shrub control and removal, such as brush management, should be considered to reduce erosion on rangelands. Current rangeland management policies and practices might need to consider changes and adapt to the increased risk of runoff and soil erosion.