A Levels-of-Evidence Approach for Assessing Cumulative Ecosystem Response to Estuary and River Restoration Programs

Abstract

Large-scale ecological restoration programs are beginning to supplement isolated projects implemented on rivers and tidal waterways. Nevertheless, the effects of estuary and river restoration often continue to be evaluated at local project scales or by integration in an additive manner. Today, we have sufficient scientific understanding to apply knowledge gained from measuring cumulative impacts of anthropogenic stressors on ecosystems to assessment of ecological restoration. Integration of this knowledge has potential to increase the efficacy of restoration projects that are conducted at several locations but comanaged within the confines of a larger integrative program. We introduce a framework based on a levels-of-evidence approach that facilitates assessment of the cumulative landscape effects of individual restoration actions taken at many different locations. It incorporates data collection at restoration and reference sites, hydrodynamic modeling, geographic information systems, and meta-analyses in a five-stage process: design, data development, analysis, synthesis and evaluation, and application. This framework evolved from the need to evaluate the efficacy of restoration projects that are being implemented in numerous wetlands on the 235 km tidal portion of the Columbia River, USA, which are intended to increase rearing habitat for out-migrating juvenile salmonid fishes.