Coupling Coordination of Built-Up Land Intensity and Green Land-Use Efficiency in Hainan Island Based on Multi-Source Heterogeneous Data Fusion

Aligning urban land development intensity with green land-use efficiency (GLUE) is crucial for fostering high-quality regional growth. This study aims to examine the coupling and coordination between built-up land intensity (BUI) and GLUE by utilizing multi-source heterogeneous data for Hainan Island (2017, 2020). A coupling coordination degree model and Geographical Detector are applied to quantify BUI, GLUE, and their coupling coordination, while also identifying the underlying driving factors. The results reveal the following: (i) Following the Free Trade Port initiative, BUI increased by 15.8%, while GLUE grew by 4.9%; (ii) The BUI–GLUE system is still in an adjustment phase, with 94% of jurisdictions showing low coordination; (iii) The primary drivers of coupling have shifted from economic fundamentals to policy and institutional guidance, with their interactions demonstrating significant synergies. These findings suggest that policy-induced land expansion may outpace improvements in GLUE, potentially leading to an imbalance in the land system. This paper introduces an innovative Driver–Response–Feedback and Production–Living–Ecological (DRF–PLE) framework and develops a transferable diagnostic tool for evaluating land-use system sustainability in rapidly urbanizing regions.