Remote Sensing Study on the Coupling Relationship between Regional Ecological Environment and Human Activities: A Case Study of Qilian Mountain National Nature Reserve

Analyzing human–environment coupling is important in understanding the mechanisms and developments of human–environment systems. However, the current frameworks and approaches evaluating the relationship between human activities and the ecological environment remain limited. Integrating the vegetation-impervious surface–soil–air framework, Mann–Kendall test, correlation analysis, two-step floating catchment area method, coupling analysis, and optimal parameters-based geographical detector, this study comprehensively evaluate the environmental changes and analyzes the coupling relationship between environment and human activities, mainly in terms of habitat quality, landscape pattern, and ecological services. The study area was the Qilian Mountain National Nature Reserve in Gansu province, China, an ecologically fragile region with an environment closely linked to human activities. Along with district and county census data, various remote-sensing products (e.g., MODIS, Landsat) were used to assess the ecological level and human–environment coupling state of the study site from 2003 to 2019. The main results show: (1) The remote sensing composite index, which integrates eight ecological sub-indices, effectively captures the spatial and temporal variations of the ecological environment in the study area, providing comprehensive and detailed environmental information. (2) Analysis using the Mann–Kendall-correlation classification, coupling degree, and two-step floating catchment area methods consistently demonstrates a gradual coordination between human activities and the ecological environment in the study area. (3) In comparison to spatially interpolated population data, the remote sensing human activity index more significantly represents the spatial impact of human activities on the ecological environment. (4) The environmental aspects most strongly associated with human activities include carbon fixation and oxygen release, vegetation, humidity, and soil. (5) The ecological environment level does not uniformly deteriorate with increasing population density, and a notable alignment is observed between changes in the ecological environment and the implementation of government environmental protection policies.