A method for evaluating ecological space and ecological conservation redlines in river basins: A case of the Yangtze River Basin

Ecological space refers to the region that aims to provide ecosystem services. Determining the scope of an ecological space is the basis for coordinating conservation and development,and ensuring sustainable supply of ecosystem services. The Yangtze River Basin is the cradle of the Chinese nation; it plays an important role in the economic development of China,and it is a biodiversity hotspot with global significance. In our study,we used the Yangtze River Basin as an example to discuss the watershed-oriented methods of ecological space planning and management policies. On the basis of analysis of the watershed hydrological path and beneficiary populations of its associated ecosystem services,we selected ecosystem service functions( water retention, flood mitigation, water purification, and soil retention) and biodiversity conservation and ecological sensitivity indicators( soil erosion,rocky desertification,and land desertification),and proposed an ecological space planning method at the watershed scale. The results showed that the area of the ecological space in the Yangtze River Basin was 102.25 × 104 km~2,accounting for 57.42% of the total area of the basin. The forest,shrub,grassland,and wetland accounted for 52.87%,19.51%,18.96%,and 4.26% of the total area of the ecological space,respectively. The ecological space of the Yangtze River Basin could conserve 79.47%,86.99%,78.09%,80.60%,and 86.49% of the total amount of the water retention service,flood mitigation service,water purification service,soil retention service,and natural habitat,respectively. On the basis of the ecological space determined by us,the spatial pattern of the ecological conservation redline was analyzed. The area of the ecological conservation redline was 59.25 × 104 km~2,accounting for 33.27% of the total area of the basin; the redline areas within the upper reaches,middle reaches,and lower reaches accounted for 59.24%,38.05%,and 2.71% of the whole redline area,respectively. Our study is not only the basis for ecological space planning of the Yangtze River Basin,ensuring the basin' s ecological safety and sustainable development of the economy and society,but also referential for similar ecological space planning of other river basins.