A Multi-Criteria Framework for Sustainable Marine Spatial Planning in Coastal Cities: Case Study in Shenzhen, China

As rapid urbanization intensified pressure on coastal ecosystems, balancing economic development with ecological preservation remained a critical challenge. This study developed a multi-criteria framework for integrated marine spatial planning and applied it to Shenzhen, China—a rapidly expanding coastal metropolis overseeing 1145 km2 of marine territory with a 260.5 km coastline, 61.47% of which has been anthropogenically modified. The methodology combined ecological, environmental, and socioeconomic indicators through a hierarchical evaluation system, using entropy-weighted indices and GIS-based spatial analysis to assess marine space suitability across three functional categories: ecological protection, urban development, and biological resource utilization. The results revealed that 38.53% of Shenzhen’s coastline retains natural geomorphology, while 23.7% annual growth in maritime infrastructure projects since 2015 highlights urgent development pressures. Marine spatial zoning identified priority areas for ecological conservation, urban–industrial expansion, and biological resource utilization through a 1 km × 1 km grid-based analysis, integrating water quality monitoring data. The framework demonstrated how adaptive zoning of underutilized coastal areas could enhance resource efficiency while balancing economic and environmental goals. These findings provide empirical evidence for optimizing marine resource allocation in coastal megacities, emphasizing the importance of data-driven planning anchored in quantitative metrics (e.g., shoreline development intensity and fisheries resource carrying indices) to achieve long-term sustainability.