Land-Use Evolution and Multi-Scenario Spatial Divergence in Bays: A Case Study of Haitan Bay and Tannan Bay, Pingtan Island, China

Conflicts between development and conservation on tourism-driven islands are concentrated in bay-adjacent terrestrial areas, yet land-use evolution and scenario responses are rarely compared among functionally distinct bays on the same island. This study examined Haitan Bay and Tannan Bay on Pingtan Island using 2 m remote-sensing images from 2008, 2016, and 2024, landscape metrics, and a coupled System Dynamics–Patch-generating Land Use Simulation (SD–PLUS) model. Natural Development (ND), Ecological Restoration (ER), and Economic Development (ED) scenarios were simulated for 2035; ER and ED outputs were further compared pixel by pixel with Minimum Mapping Unit (MMU) sensitivity testing. From 2008 to 2024, Construction Land expanded and became more aggregated in both bays, mainly at the expense of Cropland and Grassland. Relative to 2024, Construction Land increased by 1.74% and 3.97% under ER in Haitan Bay and Tannan Bay, versus 12.27% and 10.89% under ED. New Construction Land mainly extended around existing built-up areas in Haitan Bay but clustered along transportation corridors in Tannan Bay. Scenario-consistent Areas accounted for 87.56% and 89.29%, while some patch metrics were MMU-sensitive. These results reveal distinct land-use responses between Haitan Bay and Tannan Bay and support differentiated spatial planning for the two bay-adjacent terrestrial areas.