Multi-Scenario Simulation and Carbon Emission Mitigation Strategies Across Different City Types Under Regional Shrinkage: A Case Study of Heilongjiang Province, China

Against the backdrop of accelerating global climate change, land use serves as an important spatial carrier linking socioeconomic activities with ecological carbon processes, and changes in its structure and utilization patterns can affect regional carbon emissions. However, existing studies have paid insufficient attention to land-use change and the associated carbon-emission responses in the context of urban shrinkage. Taking Heilongjiang Province, China, as a case study, this study analyzes the evolution of land-use carbon emissions (LUCE) across four types of shrinking cities and growing cities from 2000 to 2020 and employs the SD–PLUS model to simulate land use and associated carbon emissions under three scenarios for 2025, 2030, and 2035. The results show that: (1) LUCE in resource-dependent and composite cities generally followed a “rise–decline–rebound” trajectory, whereas siphon-effect and location-constrained cities exhibited an overall upward trend, indicating that population shrinkage and changes in LUCE do not necessarily occur synchronously. (2) Scenario responses varied markedly across city types. Under the scenario settings adopted in this study, the smart shrinkage scenario generally achieved greater emission reductions than the ecological priority scenario in most resource-dependent, location-constrained, and siphon-effect cities, whereas the differences were relatively small or the responses differed in composite cities and some individual cities. (3) Shrinking cities should better coordinate land supply with changing demographic and economic demands while maintaining essential land functions and implement differentiated low-carbon land management according to resource-dependent, composite, location-constrained, and siphon-effect shrinkage contexts.