Multi-Scenario Land-Use Simulation and Water–Carbon Ecosystem Service Coupling for Urban Sustainability: A PLUS–InVEST Assessment in Jinan, China

In the context of rapid urbanisation, the accelerating conversion of ecological land into built-up areas has intensified conflicts between urban expansion and ecological sustainability, making accurate simulation and forecasting of land-use development increasingly important for sustainable spatial planning. This challenge is particularly urgent in cities where ecological functions are closely linked to water resources and landscape structure. The present study adopts Jinan, designated the “City of a Thousand Springs”, as a paradigmatic example of a mountain–spring–urban composite ecosystem. The study systematically analyses how disparate development pathways influence regional water yield, carbon storage, and their interactions. Land-use patterns for 2030 were simulated with the PLUS model under three scenarios: natural development (NDS), ecological spring protection (ESPS), and economic development (UDS). The InVEST model was used to quantify water yield, carbon storage and water–carbon coupling coordination for 2020 and each scenario. Results show that between 2000 and 2020, construction land expanded by 954.85 km2 while cropland declined by 632.46 km2. Rising impervious surface coverage led to modest increases in total water yield across scenarios (0.65~1.07%), with the smallest increase under ESPS. High-yield areas remained concentrated in built-up zones. Carbon storage declined by 0.41~0.75%, most notably under UDS, and maintained a stable “high south-low north” spatial pattern. Water–carbon coupling was dominated by initial to moderate coordination, while trade-off areas were mainly distributed across plains. The results provide a spatial basis for the promotion of sustainable land use, integrated ecosystem management and urban ecological security planning, offering practical insights for advancing sustainability-oriented development in rapidly urbanising regions.