The assessment of ecological restoration effects on Beijing-Tianjin Sandstorm Source Control Project area during 2000–2019

To halt the trend of desertification and improve the ecological environment in Beijing, Tianjin and surrounding areas, China establishes the ecological engineering of Beijing-Tianjin Sandstorm Source Control Project. The assessment of ecological restoration after the implementation of ecological engineering is conducive to the ensuing management of ecological engineering. Based on a large number of remote sensing data and calculation models, this study selected land use/cover, vegetation ecological quality indicators such as vegetation coverage and NPP, and other ecological service indicators such as water retention calculated by the InVEST model, soil retention by the RUSLE model, and sand fixing services by RWEQ model to comprehensively assess the degree of restoration and trend of ecological engineering implementation. The contributions of climate change and human activities to NPP and soil retention services are also assessed. We found that from 2000 to 2019, the land cover pattern is optimized, with desert and farmland turning to grassland and forest. The vegetation ecological quality has been improved, sand-fixing service have been significantly improved, and water retention and soil retention service are degraded in some areas. The areas with a high-degree restoration are mainly located in the water source protection areas in the Yanshan mountainous region and in some areas in the south-eastern Horqin Sandy Land, while the areas with a low-degree restoration are mainly located in the desert grassland. The ecological improvement areas are mainly distributed in the mountains in norther Shanxi Province, the water source protection area in the Yanshan mountainous region, the Southern Great Hinggnan Mountains and part of the agro-pastoral transitional grassland. The highly degraded areas are mainly concentrated in the middle of Horqin and Otindag Sandy Lands. Ecological engineering plays an important role in promoting ecological restoration by changing land use types. The contribution proportion of climate change to NPP and soil retention services are significantly higher than those of human activities. The degree of ecological restoration depends on the climax ecological background determined by the climate.