Wetland Compensation and Landscape Change in a Rapidly Urbanizing Context

摘要

While there are regulatory requirements that regulators should assess the impact of landscape-scale changes on the success of US Clean Water Act wetland compensatory mitigation sites, these requirements are poorly specified and very little work has been done to characterize how landscape change impacts CWA compensation sites. We created a rapid assessment method with both site-based and landscape-scale components, and used it to assess a population of wetland compensation sites in suburban St. Paul, Minnesota in 1997. We resampled the sites in 2010. The watersheds of these 22 compensation sites are characterized by rapid urbanization, the increase in impervious surfaces, and the loss of agriculture. This has resulted in extreme hydrographs at compensation sites and a fragmenting landscape context of more and smaller undeveloped patches. The ecosystem services provided by these compensation sites in 2010 are not significantly different than in 1997, indicating resilience in the face of landscape change, but not showing a trajectory of improvement. Reference sites were established for each ecosystem service, but two reference sites declined dramatically; results point to the importance of understanding ongoing landscape change even at benchmark sites. Compensation sites are typically located in rapidly changing and fragmenting landscapes, and understanding the relationship between landscape and compensation site will be important to ensuring appropriate compensation for impacts regulated by the Clean Water Act.