Integrated effects of land-use change and human–environment interactions on habitat quality in the Chengdu–Chongqing urban agglomeration: Insights from explainable machine learning and structural equation modeling

The Chengdu–Chongqing urban agglomeration is a vital area in China's regional development plan and also plays an important role in protecting the environment. As the local economy expands rapidly, the ecosystem in this region is under growing pressure. However, limited research has examined the detailed evaluation of habitat quality (HQ) and the mechanisms underlying its evolution. This study applied the InVEST model, contribution index, and spatial autocorrelation analysis, combined with XGBoost–SHAP and a structural equation model (SEM), to systematically examine the spatiotemporal variations of HQ in the Chengdu–Chongqing region and its influencing factors. The findings indicate that: (1) Between 2000 and 2020, the HQ value in this region dropped from 0.615 to 0.606, indicating a small overall downward trend. (2) Ya'an and Leshan were important high-quality habitats, while Nanchong, Ziyang, Chengdu, and the main urban area of Chongqing were representative low-level habitats; spatially, low-level habitats in the central region gradually became fragmented, and high-quality habitats expanded eastward. (3) The ranking of the main influencing factors by their contribution was slope > temperature > cropland fragmentation > forestland fragmentation > vegetation greenness > nighttime illumination > population density. During the study period, urban expansion, cropland conversion, and changes in forest land configuration jointly altered the contribution of land-use structure to modeled HQ. (4) The SEM-based path analysis further showed that slope was linked to modeled HQ through vegetation greenness and land-use configuration. This study provides an extensive analysis of how climate, vegetation, landscape and human activities work together to affect HQ amid changes in land use. The findings provide practical evidence to help balance urban growth and ecological conservation as the Chengdu–Chongqing region undergoes rapid urbanization.