Agricultural conservation practices increase wetland ecosystem services in the Glaciated Interior Plains

The Glaciated Interior Plains historically supported a broad variety of wetland types, but wetland losses, primarily due to agricultural drainage, range from 50% to 90% of presettlement area. Wholesale land use change has created one of the most productive agricultural regions on earth, but wetland conversion has also led to the loss of the ecosystem services they provide, particularly water quality improvement, flood de-synchronization, carbon sequestration, and support of wetland-dependent species (biodiversity). Nearly three-quarters of the Glaciated Interior Plains fall within the Mississippi River drainage basin, where the combination of extensive tile drainage and fertilizer use has produced watersheds that contribute some of the highest nitrogen yields per acre to the Mississippi River. Wetland conservation practices implemented under Farm Bill conservation programs have established or involved management of nearly 110 000 ha of wetlands, riparian zones, and associated ecosystem services over the period 2000–2007. We estimated the cumulative ability of these conservation practices to retain sediment, nitrogen, and phosphorus in Upper Mississippi River Basin watersheds. Estimated retention amounts to 1.0%, 1.5%, and 0.8% of the total N, sediment, and P, respectively, reaching the Gulf of Mexico each year. If nutrient reduction is estimated based on the quantity of nutrients exported from the Glaciated Interior Plains region only, the numbers increase to 6.8% of N, 4.9% of P, and 11.5% of sediment generated in the region annually. On a watershed basis, the correlation between the area of wetland conservation practices implemented and per-hectare nutrient yield was 0.81, suggesting that, for water quality improvement, conservation practices are successfully targeting watersheds that are among the most degraded. The provision of other ecosystem services such as C sequestration and biodiversity is less well studied. At best, implementation of wetland and riparian conservation practices in agricultural landscapes results in improved environmental quality and human health, and strengthens the rationale for expanding conservation practices and programs on agricultural lands.