Effects of climate change and wildfire on soil loss in the Southern Rockies Ecoregion

Forests in the Southern Rockies Ecoregion surround the headwaters of several major rivers in the western and central US. Future climatic changes will increase the incidence of wildfire in those forests, and will likely lead to changes in downstream water quality, including sediment loads. We estimated soil loss under the historic climate and two IPCC climate change emissions scenarios (A2 and B1); each scenario was modeled using statistically downscaled climate data from global circulation models (GCMs; ECHAM5 and HadCM3) for each of thirteen land cover types. We used the Revised Universal Soil Loss Equation (RUSLE) and developed a way to calculate rainfall erosivity, a key factor in RUSLE, to account for climate change. We also incorporated the effects of climate change on wildfire to create stochastic spatial distributions of wildfires and to inform changes in land cover. Based on 100 simulations of future wildfire applied to RUSLE for each GCM-scenario combination, we found that soil loss will likely increase above historic levels but that considerable uncertainty remains about the amount of increase. Across the GCM-scenario combinations, mean soil loss increased above historic levels by from 3% (HadCM3-A2) to 65% (ECHAM5-B1) for climate change only and the effects of wildfire increased soil loss an additional 3 to 5%.