Structural and Functional Loss in Restored Wetland Ecosystems

David Moreno-Mateos,Roxana Yockteng,Mary E Power,Francisco A Comín,Michel Loreau

doi:10.1371/journal.pbio.1001247

Abstract

Author SummaryWetlands, which include tropical mangroves and boreal peatlands, are among the most valuable ecosystems in the world because they provide critical ecosystem goods and services, such as carbon storage, biodiversity conservation, fish production, water purification, and erosion control. As global change accelerates the loss of wetlands, attempts are increasing to restore this fragile habitat and its associated functioning. There has been no global evaluation, however, of how effective such restoration efforts have been. Here, we present a meta-analysis of the biological structure (driven mostly by plant communities) and biogeochemical functioning (driven primarily by the storage of carbon in wetland soils) of 621 wetland sites. Our analysis suggests that even a century after restoration efforts, these parameters remained on average 26% and 23% (respectively) lower in restored or created wetlands than in reference wetlands. Our results also indicate that ecosystem size and the environmental setting significantly affect the rate of recovery. Recovery may be more likely and more rapid if more than 100 contiguous hectares of habitat are restored. In warm climates, and in settings linked to riverine or tidal flows, recovery can also proceed more rapidly. In general, however, once disturbed, wetlands either recover very slowly or move towards alternative states that differ from reference conditions. Thus, current restoration practice and wetland mitigation policies will maintain and likely accelerate the global loss of wetland ecosystem functions.

Highlights

From tropical mangroves to boreal peatlands, wetlands are amongst the most productive and economically valuable ecosystems in the world [1]
Owing to human activities, over half of the wetland ecosystems existing in the early 20th century have been lost in North America, Europe, Australia, and China [2]
We need more realistic, long-term evaluations to find better ways to alleviate constraints limiting the recovery of wetland ecosystems

Summary

Introduction

From tropical mangroves to boreal peatlands, wetlands are amongst the most productive and economically valuable ecosystems in the world [1]. Restoration of degraded wetlands and creation of new ones have been attempted, in efforts to recover physical, chemical, and biological processes and entities lost because of wetland destruction or degradation [4]. This approach does not restore ecosystem structure and functions to preimpact levels [5,6,7,8]. After degradation or natural perturbation, ecosystem structure and functions recover towards reference levels [7,12], but recovery rates might be affected by the physical characteristics of the ecosystem, the degrading activity, or the environmental setting [7,12]. We compared structure and function of 401 wetlands restored on sites where they had been previously degraded and 220 newly

Author Summary

Conclusions

Findings

Materials and Methods