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Sediment retention by natural landscapes in the conterminous United States
Citation:
Woznicki, S., P. Cada, J. Wickham, M. Schmidt, J. Baynes, M. Mehaffey, AND A. Neale. Sediment retention by natural landscapes in the conterminous United States. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 745:140972, (2020). https://doi.org/10.1016/j.scitotenv.2020.140972
Impact/Purpose:
The objectives of this study were: (1) develop a high-resolution (30-meter) map of soil erosion in the conterminous United States, and (2) quantify the soil retention service that natural vegetation provides at that same resolution. Understanding erosion and the retention of soil on the landscape is a critical factor relating to food and water security and contaminant transport.
Description:
Soil functions provide vital ecosystem services, from sequestering carbon to providing food and moderating floods. Soil erosion threatens the provisioning of these services while deteriorating downstream water quality. Vegetation plays an important role in soil retention – by holding it in place and preventing erosion, soil can continue to provide important ecosystem goods and services while water resources are protected. Using the Revised Universal Soil Loss Equation (RUSLE) driven by open-source physiographic and remote sensing datasets, we estimate sheet and rill erosion caused by precipitation. We also developed a national map of sediment delivery ratio (SDR) to connect erosion on the landscape to delivery to waterbodies. SDR considers both the upslope and downslope hydrologic connection of a pixel to its draining waterbody and its upstream catchment characteristics. The estimated annual average sheet and rill erosion in the conterminous United States was 1.55 Pg yr-1, of which one third (0.51 Pg yr-1) reached waterbodies. Natural land cover prevents 12.3 Pg yr-1 of sheet and rill erosion, which amounts to 5 Pg yr-1 in avoided sediment delivery to waterbodies. The value of natural land cover in retaining sediment and preventing its delivery downstream once waterborne is not just a function of the land cover characteristics, but of its physiographic characteristics and spatial context (e.g., topography, climate, hydrologic connectivity), resulting in spatially variable sediment retention values within land cover classes. This study may have implications for prioritizing where natural land cover should be preserved, or agricultural land taken out of production to minimize delivery of sediment to waterbodies.
