Ecosystem-Service Changes During Ecological Restoration and Urban Expansion in a Medium-Sized Hilly City: A Case Study of Nanchong, China

Understanding how ecological restoration and urban expansion jointly reshape ecosystem-service patterns remains challenging in medium-sized inland hilly cities undergoing rapid land-use change. Nanchong, a representative hilly city in southwestern China, provides an opportunity to examine changes in ecosystem services associated with restoration-related land-use transformation and urban development. Using multisource spatial data and the InVEST model, this study quantified changes in soil conservation, carbon storage, water yield, and habitat quality from 2018 to 2023 and established an integrated ecosystem-service zoning framework. Results showed substantial land-use restructuring during the study period, characterized by forest expansion and cropland reduction. Soil conservation increased by 9.52 × 106 t (30.5%), and carbon storage increased by 2.38 × 106 t (3.72%), with the major improvements concentrated in forested hilly regions. Water yield increased by 339.60 × 106 m3 (43.3%), although this change was strongly associated with interannual precipitation variability. Mean habitat quality increased from 0.4443 to 0.4801, while the concurrent increase in habitat degradation indicated increasing spatial differentiation between restored areas and urban fringes. Integrated ecosystem-service zoning revealed a transition from medium-service dominance toward greater spatial polarization, with the proportion of relatively high- and high-service areas expanding from 14.54% to 23.20%. These findings indicate that restoration-related land-use changes were associated with increases in multiple ecosystem services but did not fully offset urbanization pressures, highlighting the need for spatially differentiated green-space management in hilly cities.