Evaluating combined effects of socio-economic development and ecological conservation policies on sediment retention service in the Qiantang River Basin, China

The rapid socio-economic development and various ecological conservation policies in China have significantly affected sediment yield in the large basin. However, how these two aspects of influencing factors jointly drive the dynamics of sediment retention service is still poorly understood, although it is critical to evaluate ecosystem service dynamics and realize the balanced relationships between human activities and aquatic ecosystem health. Integrating the revised universal soil loss equation (RUSLE) model and sediment delivery ratio (SDR) model, this study evaluated dynamics of sediment retention service driven by combined factors of socio-economic development and ecological conservation policies. Furthermore, the relative contribution analysis identified contributions of these drivers to sediment dynamics. Results indicated that (1) sediment retention service improved from 2000 to 2015 in the Qiantang River Basin, with a 39.89% reduction in sediment export. (2) Ecological conservation policies played a more critical role in this improvement than socio-economic development. (3) In particular, the Green Project made the major contribution to controlling sediment export among all the drivers, additionally, increasing grain yield (per unit area) benefited sediment retention service because it mitigated the substantial demand for farmland and the excessive deprivation of ecological lands. (4) The emerging Ecological Conservation Red Line (ECRL) policy could reduce sediment export inside the redline regions by 84.13% through future scenario analysis, providing practical guidance for exploring more ecological benefits. Finally, suggestions for formulating targeted ecological protection policies and sustainable socio-economic plans were proposed to promote aquatic ecosystem services and strengthen ecological security in the large basin.