The Response of Ecosystem Services to Human Activity Intensity and Its Constraining Effects in the Karst Region of Southwest China

The southwest karst region of China is characterized by unique landscape patterns, a fragile ecological environment, and intense human disturbances. Identifying the spatial heterogeneity of ecosystem services (ES) and exploring the spatiotemporal correlations between ES and human activity intensity are crucial for achieving sustainable development. However, previous studies have often overlooked the complex spatiotemporal dynamics and nonlinear relationships between human activities and ES. To address this gap, this study selected four key ES indicators, namely water yield (WY), soil retention (SR), net primary productivity (NPP) for carbon storage, and biodiversity index (BI). Combined with the Human Footprint Index (HFI), we evaluated the spatiotemporal evolution of ES and their responses to human activity intensity. The results show that from 2000 to 2020, the total ecosystem services (TES) in the southwest karst region exhibited a fluctuating upward trend, with an increase of 20.26%. The central part of Guizhou Province witnessed the most significant improvement. During the same period, HFI increased by 12.84%. Nevertheless, TES and HFI showed a significant negative correlation in 55.05% of the study area. Threshold analysis revealed a hump-shaped nonlinear relationship and threshold effects between TES and HFI, indicating that moderate HFI can promote the enhancement of ES, but once the threshold is exceeded, ES will decline. The responses of TES to HFI varied significantly across different regions, reflecting the heterogeneity and vulnerability of the karst ecological environment. This study quantifies the threshold-based constraint relationship between ES and HFI in the southwest karst region, providing both theoretical support and practical pathways for formulating differentiated management strategies in ecologically fragile areas.