The Jialing River watershed has seen substantial changes in habitat quality and land use throughout the last 20 years. It is yet unknown, however, how the habitat quality will react to these changes in land use. In this work, multi-scenario simulations for 2030 were carried out using the PLUS and InVEST models, and the land use changes and habitat quality evolution in the Jialing River basin from 2000 to 2020 were evaluated. In this study, the following facts were determined: (1) The study area’s southern region is mainly farmland, whereas the northern part is predominantly forestland. The most significant changes were a decrease of 1.46% in the grassland and an increase of 1.07% in the construction land. (2) The northern area typically has greater habitat quality than the southern region, at habitat quality indices of 0.5401, 0.5338, and 0.5084 for the year 2000, the year 2010, and the year 2020, respectively, demonstrating a pattern of steady decline. (3) Converting farmland to forestland can successfully increase habitat quality, but the conversion of grassland and forestland to farmland is the primary cause of the decline of habitat quality. (4) Global Moran’s indices of −0.7809, −0.7537, and −0.6376 for 2000, 2010, and 2020, respectively, were found in the correlation study between habitat quality and land use intensity, showing a high negative link. The local indicators of spatial association (LISA) maps indicated that the northern region had high land use intensity with low habitat quality, while the southern region had low land use intensity with low habitat quality. (5) The outcomes of the multi-scenario simulations show that, except under the ecological conservation scenario (0.5123) where habitat quality improved, there was a certain degree of deterioration under the business-as-usual (0.4381), farmland conservation (0.4941), and sustainable development (0.4909) scenarios. For future sustainable development, strict control of the encroachment on farmland and forestland is recommended, alongside the adoption of proactive measures to improve habitat quality.

Soil erosion is a major environmental issue that threatens watershed ecological security and the sustainable use of land resources. Quantifying its spatiotemporal variability and associated environmental controls is important for sustainable land use planning and watershed management. To characterize the spatiotemporal variation in CSLE-simulated soil erosion and the relative explanatory contributions of environmental variables in the Qingyi River Basin, this study integrated rainfall, soil type, digital elevation model, land use, and vegetation coverage data for six observation years from 2000 to 2025 with GIS spatial analysis and the Chinese Soil Loss Equation (CSLE). Geodetector and CatBoost–SHAP were further applied to evaluate the explanatory contributions and interaction patterns of the selected environmental variables on the simulated erosion results. The results showed the following: (1) Woodland and cropland dominated the land use structure of the basin, while construction land increased from 90.95 km² to 164.21 km². Land use patterns differed markedly between the upstream and downstream areas, with woodland and grassland dominating the upstream area and cropland and construction land accounting for higher proportions in the downstream area. (2) Across the six observation years, the mean soil erosion modulus ranged from 135.74 to 378.39 t·km⁻²·a⁻¹, indicating generally low erosion levels, with the highest value occurring in 2015 and the lowest in 2025. (3) Soil erosion intensity was mainly characterized by slight and mild erosion, which together accounted for more than 95% of the basin area, whereas areas of moderate erosion and above were mainly concentrated in downstream mountainous areas and along both sides of river valleys. (4) The explanatory analysis showed that elevation, land use, and vegetation coverage made relatively high contributions to the spatial variability in the CSLE-simulated erosion results. Topographic and vegetation-related variables showed higher explanatory contributions in the upstream area, whereas land use showed a higher contribution in the downstream area. These findings provide a quantitative basis for soil erosion monitoring, the identification of priority areas for soil and water conservation, sustainable land use optimization, and region-specific watershed management in the Qingyi River Basin.