Wetlands Restoration Failing to Reestablish Pristine Conditions
By Erin Weaver
A new meta-analysis published in PLoS Biology, “Structural and Functional Loss in Restored Wetland Ecosystems,” reveals the relative ineffectiveness of wetlands restoration over the last century. Data from 621 sites throughout the world show that even 100 years after restoration attempts, wetlands’ biological structure and biogeochemical functions (such as carbon storage in soil) achieved only 74%–77% those of reference sites.
Wetlands larger than 100 contiguous hectares recovered more rapidly, as did those in warmer climates or with more hydrologic exchange from rivers or tidal flows. Return to reference conditions could simply take longer than a century, or the disturbed wetlands may have established alternate states, potentially due in part to climate change.
A June 2010 article in Wetlands, “The Potential of Integrated Constructed Wetlands (ICWs) to Enhance Macroinvertebrate Diversity in Agricultural Landscapes,” makes an alternative case: chains of ponds used to treat agricultural wastewater in Ireland support a range of wildlife similar to that found in natural wetlands, helping meet EU water body targets of similarity to pristine conditions. Given that wetlands with greater water exchange performed better in the restoration study, a combination of restored and constructed habitats could prove key to maintaining functional wetlands.