Spatiotemporal changes and degradation early-warning of key ecosystem services in China from 2015 to 2020.

Change assessment and degradation early-warning of Key Ecosystem Services (KES) provide a vital scientific foundation for addressing ecological degradation challenges and optimizing ecological governance policies. Counties are the fundamental unit for spatial governance and ecological policy implementation in China. However, the spatiotemporal dynamics and degradation risks of KES at this scale have not been systematically assessed in the context of ecological civilization construction. Focusing on the critical stage of China’s ecological civilization construction from 2015 to 2020, this study took all counties nationwide as the basic units to systematically analyze the spatiotemporal dynamics of three KES: water conservation (WC), soil conservation (SC), and windbreak and sand fixation (WSF). Furthermore, a fact-based ecological degradation early-warning model was developed to enable the precise identification of degraded areas and their respective warning levels. The results showed that: (1) From 2015 to 2020, the three KES nationwide exhibited a trend of overall stability coupled with a slight increase. Spatially, high-value zones for WC were primarily concentrated in the Qinghai-Tibet Plateau (QTP), southern mountainous regions, and key forest zones of Northeast China. High-value zones for SC were predominantly distributed across the Loess Plateau, QTP, Yunnan-Guizhou Plateau, and southeastern hilly and mountainous regions. WSF, in contrast, were highly concentrated in the arid and semi-arid regions of Northern China and the QTP. (2) The ecological degradation early-warning results indicate that 48.96% of counties nationwide were in a “no alert” state, while the remaining counties exhibited varying degrees of functional degradation. Among these, counties under light, moderate, and severe alerts accounted for 36.97%, 12.26%, and 1.83%, respectively. Severe-alert areas were mainly distributed in the extremely arid regions of Northwest China and the karst mountains of Southwest China, largely driven by the substantial degradation of SC functions. Based on these alert types and priority regions, this study proposes tiered ecological governance policy recommendations. Our proposed early-warning framework facilitates the intuitive and efficient identification of county-level KES degradation risks. Thus, the findings offer a scientific foundation for formulating targeted strategies for ecological conservation and restoration in territorial spatial planning.