An Ecosystem Service Approach to Inform Reactive Nitrogen and Groundwater Management

Ecosystem service valuation (ESV) allows for the identification of the location of services provided by natural ecosystems along with an economic measure of their significance. While this provides an important function in terms of land use management, the connection between ecosystem services, sensitivity to nitrogen loading and nitrogen load estimates is unexplored within ESV literature and research on nutrients and ecosystem services. This research combines a GIS-based, value transfer approach to map ecosystem services in the Lower Yakima River Basin (LYRB), along with estimates of nitrogen loading to identify how nitrogen management affects ecosystem services. This analysis combines ecosystem service values with nitrogen loading and identifies regions within a Groundwater Management Area susceptible to reductions in ecosystem services due to nitrogen loading. Based on this analysis, wetlands and forested areas have disproportionately high values of ecosystem services in the LYRB, while pasture and cultivated crops contribute less to total ecosystem service flows. Estimated nitrogen loads are also driven by the location of CAFOs and cultivated crops. The hydrologic setting of these land uses in relation to ecosystem services is a critical component to understanding changes in ecosystem services. Areas of high nitrogen loading and high ESV highlight specific opportunities for achieving immediate success maintaining ecosystem services through regulatory mechanisms. However, the land cover analysis neglects the values of subsurface processes and groundwater resources in ecosystem service assessment, so an econometric model is applied to estimate willingness to pay to maintain given nitrate levels in private wells. The exclusion of groundwater resources is clearly a major problem in existing literature and this research attempts to include these resources where they have been neglected. Through the incorporation of WTP estimates for groundwater quality, a more complete economic and ecological perspective on the effects of N loading is highlighted.