The cost effectiveness of wetlands designed and sited for nitrate removal: The effect of increased efficiency, rising easement costs, and lower interest rates

Abstract

D ue to the persistent hypoxic zones in the Gulf of Mexico, Chesapeake Bay, and elsewhere, and the completion of Conservation Effects Assessment Project reports for the Upper Mississippi River, Chesapeake Bay, and Ohio and Tennessee river basins, interest has increased in identifying cost-effective ways to address agricultural nitrogen (N) loadings. Each of these Conservation Effects Assessment Project reports reveals that, despite substantial conservation investments in these river basins, soluble N continues to leave agricultural lands at high levels (NRCS 2011a, 2011b, 2012). These findings draw greater attention to relatively novel conservation systems, such as saturated buffers, bioreactors, and wetlands designed and sited to intercept and reduce N runoff (figures 1, 2, and 3). Crumpton et al. (2007) estimated that 0.2 to 0.4 million ha (0.5 to 1.1 million ac) of strategically situated wetlands could reduce the nitrate (NO3) loads from the Upper Mississippi and Ohio river basins by 30%, but did not examine the cost effectiveness of this approach. A 2008 examination of the cost effectiveness of wetlands designed and sited for N removal estimated the cost to be US$1.32 lb−1 (US$2.91 kg−1) (Iovanna et al. 2008), making wetlands a cost-effective approach to reduce N loadings in watersheds dominated by…