Spatiotemporal Trade-offs of Ecosystem Services and Shoreline Gradient Effects in the Yangtze River Basin

The Yangtze River Basin is a crucial ecological security barrier in China. However, the combined effects of rapid urbanization and ecological restoration policies have complicated the evolution mechanisms of ecosystem services (ESs), particularly the gradient responses in the riparian zone—a sensitive land–water interface. This study evaluated the spatiotemporal dynamics of five key ESs (water yield, soil conservation, water purification, carbon sequestration, and biodiversity) from 2000 to 2020 using InVEST, RUSLE, CASA models, and Geodetector. We focused on the gradient effects within 0–30 km of the mainstream shoreline and the trade-offs/synergies among ESs. Results showed: (1) ESs generally improved over the two decades, but with significant spatial heterogeneity and phase differences. (2) Significant synergies existed between carbon sequestration and soil conservation, and between biodiversity and soil conservation (p<0.01), while water yield was negatively correlated with carbon sequestration and biodiversity, revealing a hydrological–ecological trade-off (“greening increases water consumption”). (3) The 0–5 km near-shore zone was the most sensitive area, exhibiting the largest increases in soil conservation (63.8%) and water yield (97.8%), but also the greatest pressures on carbon sequestration (-24.8%) and biodiversity (-6.0%). This study elucidates the spatiotemporal differentiation of ESs and the sensitivity of shoreline zones in the Yangtze River Basin. We recommend consolidating restoration achievements in the 0–5 km zone, extending them into continuous corridors, and implementing hierarchical management of agricultural non-point sources and human activities in the mid-lower reaches, providing a gradient-based scientific basis for watershed ecological restoration and spatial planning.