Wetlands mitigation in the United States: assessing the success of mitigation policies

Over most of the past 200 years, wetlands were viewed as useless or worse and about 50% of the original wetlands in the United States were destroyed. Over the past few decades, as the ecological and economic values of wetland habitats have been increasingly recognised, a variety of laws and policies (most notably Section 404 of the Clean Water Act) have been adopted to protect wetland reseources. Mitigation is the cornerstone of these policies, whereby wetlands losses are compensated by wetland restoration, creation or enhancement. Recent surveys show that mitigation policies have reduced the rate of wetland losses, but they have not achieved the goal of “no net loss”. Most of these surveys have relied on permit files or simple field visits. These studies show that the area of wetland proposed for mitigation often does not meet the area impacted. In addition, few mitigation projects are in compliance with all of their permit conditions. The picture is even worse when one considers the ability of restored wetlands to replace natural wetlands functions. Several qualitative assessments of wetland mitigation projects in California indicate that some projects produce high quality habitat, but most are moderate quality and some are very low quality. A quantitative functional assessment of riparian mitigation projects in Orange County, California showed that none of the mitigation projects were successful from a functional perspective. To prevent continued wetland losses, permit conditions must focus on wetland functions, migration ratios (the area of mitigation required compared to the area lost) must be larger, permit conditions must be enforced, and monitoring and remediation must be improved.