General trends in freshwater ecological restoration practice in China over the past two decades: the driving factors and the evaluation of restoration outcome.

Background: Although freshwater ecological restoration (FER) has undergone an immense development over the past two decades in China either in the number of projects or in the spatial scale of implementations, a dearth of clear and comprehensive trends in this field is still a particular concern. We conducted a literature survey through searching the database of Web of Science between 1997 and 2017 to investigate the driving force behind FER practice and to summarize the restoration outcomes. Results: A total of 2047 publications were hit and 198 of them were finally retained after manual screening. The number of studies in this field has been steadily increasing in recent years and their provincial distribution is positively correlated with GDP growth and the investment to pollution control and environmental protection, suggesting that economic development is a key driving factor of FER practice. Among the remaining articles, nearly half (46.5%) focus on lake ecosystems, and 34.8% and 32.8% of the studies indicate that land reclamation and eutrophication are the predominant causes of freshwater ecosystem degradation. The overarching target of the restoration is biodiversity increase (31.4%), followed by water quality improvement (24.7%) and ecosystem services (23.9%). Revegetation is a dominant restoration approach (40.9%). Reference sites for assessment of restoration projects are normally control locations without intervention (60%), or the status of the targeted sites before the interventions. For the restoration outcome evaluation, 86% of the studies present positive outcomes in terms of water quality improvement, and 79% have improvement in biological features. The most frequently monitored organisms are macrophytes (31%), followed by benthos as indicators of ecological condition. Conclusions: Economic growth, water pollution and investment into environmental protection are the main driving factors of FER practice in China. The effort of restoration and evaluation over the past two decades has not been limited to improving hydrological function and water quality, but also pay increasingly more attention to biological processes and ecological integrity, and further the ecosystem services in recent years. However, the lack of long-term monitoring and socioeconomic attributes considered in restoration success assessments are still particular issues that need to be addressed in the future FER researches and projects. [ABSTRACT FROM AUTHOR]