Unravelling the effects of large-scale ecological programs on ecological rehabilitation of China's Three Gorges Dam

摘要

The Three Gorges Dam (TGD) is one of the world's most controversial infrastructure projects due to substantial ecological issues. This study evaluates the effects of three major ecological programs - terrestrial ecosystems, water pollution prevention, and ecological operation - on ecological rehabilitation of the TGD. Extensive observed data on soil erosion, forest cover, water quality, sediment, spawning size of four domestic fish species, other fish species, and endemic fish species are used for the analysis. The results show that these programs significantly improved ecological functions in the Three Gorges reservoir area (TGRA), returning 2,118.47 km(2) of sloping cropland to forest or grassland, controlling 2,196 km(2) of soil erosion, and increasing forest coverage from 22% in 1997 to 49% in 2016. Water pollution prevention reduced NH3-N (ammonia nitrogen) and COD (chemical oxygen demand) pollutant emissions into the reservoir, by 87.5% and 38.5%, respectively, over the 1997-2016 period. Since 2011, water quality in the mainstream of the Yangtze River has remained stable while water quality in the tributaries of the reservoir area has improved substantially. Ecological operations dramatically enhanced fish reproduction, increasing annual average spawning stock of four domestic fish species in 2011-2016 by 137.4% on the 2003-2010 level. The findings suggest that mitigation policies can rehabilitate ecosystems and reverse some negative effects of large dams. Nuanced understandings of the relationship between ecological programs and emerging consequences of their implementations are a necessary baseline for China's policymakers and agencies as they work toward more targeted ecological rehabilitation practices and programs - and for other countries, to learn useful experience and lessons from China's policy interventions. (C) 2020 Elsevier Ltd. All rights reserved.