Sensitivity of soil loss to climate change in the Inland Northwest USA

Climate variability and anthropogenic climate change present challenges in achieving sustainable agriculture. One of the challenges in maintaining a healthy agroecological system is abundant topsoil and limited soil erosion. In the Inland Northwestern United States temperatures are expected to increase by 1.5--4°C and cool season precipitation is expected to increase 5--10% by the mid-21st century. The sensitivity of soil loss to projected changes in climate was simulated using the Water Erosion Prediction Project (WEPP) model. Sensitivity experiments were performed by running WEPP simulations for a variety of hillslopes and both conventional and no-till cropping practices by altering temperature, precipitation and precipitation extremes from a baseline climate representative of Moscow, Idaho using a continuous winter wheat rotation. Warming experiments enhanced erosion loss through indirect processes such as changes in precipitation phase and soil erodibility. In contrast, precipitation impacted soil loss directly. Projected changes in soil loss were also estimated by forcing WEPP with downscaled climate projections from 20 global climate models (GCM) from the fifth Coupled Model Intercomparison Project for both late 20th century and mid-21 st century climate forcings. Increased soil loss rates were simulated by all GCMs for mid-21st century runs compared to late 20th century conditions. These model results suggest increases in soil loss rates under future climate change that will present additional challenges to agricultural sustainability and prompt adaptation practices to conserve soil.