Riparian forest ecosystems as filters for nonpoint-source pollution

Riparian (streamside) ecosystems have been the subject of ecosystem research for about the last twenty years. Ecosystem research has shown that riparian areas are especially effective controllers of nitrogen and sediment movement to streams and other water bodies. Nitrogen control is primarily the result of biotic processes. Sediment control is primarily caused by physical processes that are enhanced by such biotic interactions as enhanced infiltration and leaf litter at the soil surface. Riparian areas are increasingly being used as a landscape- and watershed-management technique to reduce the risk of pollution and to create and preserve healthy stream ecosystems. The management practices recommended for riparian areas are based on ecosystem research. Riparian ecosystem policies and management are a success story for the application of ecosystem science to real-world problems. Riparian ecosystem research has been used to develop generalized management practices for USDA action agencies such as the Natural Resources Conservation Service and the Forest Service. Ecosystem-management recommendations for riparian areas have been incorporated into such programs as the Coastal Zone Management Act Reauthorization and the Chesapeake Bay Program. The USDA has incorporated riparian policies into the Conservation Reserve Program (CRP) reauthorized in the 1996 Farm Bill. The CRP allows farmers to voluntarily enroll such environmentally sensitive lands as riparian ecosystems because of the high environmental benefits associated with riparian areas compared to other lands. The success of riparian ecosystem research in shaping riparian policy and management results from multiple factors including: agreement among major studies on the effectiveness of riparian ecosystems for nonpoint-source pollution control; flexibility of management practices; and use of riparian ecosystems for multiple functions.