Have wet meadow restoration projects in the Southwestern U.S. been effective in restoring geomorphology, hydrology, soils, and plant species composition?

Wet meadows occur in numerous locations throughout the American Southwest, but in many cases have become heavily degraded. Among other things they have frequently been overgrazed and have had roads built through them, which have affected the hydrology of these wetland ecosystems. Because of the important hydrologic and ecological functions they are believed to perform, there is currently significant interest in wet meadow restoration. Several restoration projects have been completed recently or are underway in the region, sometimes at considerable expense and with minimal monitoring. The objective of this review was to evaluate the effects of wet meadow restoration projects in the southwestern United States on geomorphology, hydrology, soils and plant species composition. A secondary objective was to determine the effects of wet meadow restoration projects on wildlife. Electronic databases, internet search engines, websites and personal contacts were used to find articles of relevance to this review. Articles were filtered by title, abstract and full text. Summary information for each of the articles remaining after the filtering process was compiled and used to assess the quality of the evidence presented using two different approaches. Our searches yielded 48 articles, of which 25 were published in peer-reviewed journals, 14 were monitoring or project reports, and 9 were published in conference proceedings or are unpublished theses or manuscripts. A total of 26 operational-scale restoration projects were identified. A wide range of restoration techniques were employed, ranging from small-scale manipulations of stream channels (e.g., riffle structures) to large scale pond-and-plug projects. Other common restoration techniques included fencing to exclude livestock (and sometimes also native ungulates), other forms of grazing management, seeding, and transplanting seedlings. Most of the articles reported that restoration was fully or partially effective, at least in the short-term. However, the relative lack of high quality quantitative data, and especially data extending more than two years after project implementation, greatly limits our ability to determine how effective restoration has truly been in practice. While caution is warranted due to data quality limitations, progress has been made over the past 20 years in wet meadow restoration. In particular, important contributions have been made in restoring the highly degraded wet meadow systems that are characterized by deep, wide and relatively straight gullies. There is evidence, for example, that the pond-and-plug approach is an effective technique for restoring many aspects of these systems, albeit at the cost of creating new features (ponds) that are not necessarily natural features of wet meadows. There is a need to allocate additional effort to project documentation, including better-designed and longer-lasting monitoring programs. One approach that might help is for practitioners to work with scientists from government agencies, local universities and colleges, and other organizations. When this type of collaboration has happened in the past it appears to have been effective. Many important lessons could have been learned, and mistakes avoided, if more effort had been put into documenting both successes and failures of past projects.