Evaluating the progress of engineered tidal wetlands

Abstract

New terminology is needed for the assessment of wetland restoration projects, focusing on progress towards ecological goals rather than the yes/no alternative of success versus failure. Mitigation projects should be evaluated based on ‘compliance’ of specific mitigation criteria. Peer-reviewed assessments of wetland restoration projects have focused on appropriate parameters (topographic, hydrologic, soil, vegetation, and animal components); however, for the most part, they have evaluated small, newly restored wetlands over the short-term with little repeated sampling. Future assessments should focus on understanding problems at a particular site by identifying cause–effect mechanisms. We review a case study from San Diego Bay where detailed assessments led to the identification of problems and subsequent management alternatives. We also recommend the use of two novel approaches: experimentation and the evaluation of ecosystem resiliency to unplanned disturbances. These assessments will provide a better understanding of ecosystem functioning and enhance current comparisons of natural and restored systems. A stronger science base for wetland restoration and adaptive management do not guarantee that restoration targets will be reached; however, these approaches will identify the causes of problems and allow us to predict whether or not restoration targets can be reached in a timely manner.