Spatiotemporal Changes of Ecosystem Services under Horizontal Ecological Compensation: A Case Study of Miyun Reservoir Basin

Horizontal ecological compensation is a key policy instrument for incentivizing the sustained supply of ecosystem services. It is also a crucial approach for achieving the goals of ecological and environmental protection, balanced regional development, and social equity. This study explores the spatiotemporal changes in the ecosystem services of the Miyun Reservoir Basin in the context of the Beijing-Hebei transboundary horizontal ecological compensation policy. Four types of ecosystem services, namely, grain production, water yield, carbon sequestration, and soil retention, were quantitatively evaluated based on InVEST models and the spatial analysis method of ArcGIS in Miyun Reservoir Basin from 2010 to 2023. The key findings include three main points. (1) After the implementation of the horizontal compensation policy (2018–2023), the water yield, carbon sequestration, and soil retention services showed significant recovery, with a notable increase in grain production, thus validating the effectiveness of the “incentive-feedback” dynamic mechanism. Economic inputs and institutional constraints drove the regulation of human activities, which enhanced ecosystem services, while ecosystem service improvements reciprocally supported the optimization of policy, forming a virtuous cycle of “policy incentives and institutional constraints - economic inputs - green actions”. (2) The spatiotemporal heterogeneity of ecosystem services was significant. Temporally, all four services exhibited upward trends after 2018, but the reduced precipitation in 2023 triggered anomalous fluctuations in water yield and soil retention, highlighting the interference of climate change with policy outcomes. (3) Spatially, grain production migrated toward the upper reaches of the Chaohe River and Baihe River, water yield was clustered in the upper Baihe and Chaohe sub-basins, carbon sequestration was extended to the mountainous areas with the expansion of forestland, and soil retention showed a pattern of high in the middle and low in the east and west, reflecting the spatial and temporal heterogeneity of ecosystem services throughout the basin. Finally, this study proposes differentiated watershed governance and ecological compensation paths, and recommends tailored compensation standards for ecological functional zones, as well as targeted mechanisms for cropland protection, water conservation, and carbon sink enhancement. A climate-adaptive policy framework should be established to address future uncertainties and optimize Beijing-Hebei transboundary horizontal ecological compensation policies.