A spatial decision framework for coastline restoration prioritization: integrating ecosystem dynamics, stability, and ecological capacity

Coastal protection and restoration are essential for achieving sustainable development in coastal regions facing intensifying climate and development pressures. However, under the implementation of coastline occupation-compensation balance policies, the lack of systematic approaches for identifying restoration priority areas remains a major challenge. We developed a multi-dimensional spatial decision framework to identify Priority Areas of Coastline Restoration (PACR) for the mainland coastline of Shandong Province, China, based on Landsat imagery (1984-2025, 30-m resolution). The framework integrates three key dimensions: Coastline Fragmentation Degree (CFD), Stability of Coastline (SC), and Coastal Ecological Carrying Capacity (CECC), enabling a comprehensive assessment of restoration priorities under heterogeneous coastal conditions. Our results revealed that: (1) CFD exhibited significant scale dependency, following a power-law scaling relationship with observational scale (R²>0.98), indicating that coastline fragmentation assessment is highly sensitive to spatial scale. (2) SC displayed pronounced spatial heterogeneity, with high- and extremely-high-stability areas accounting for 33.74% and 25.92% of the total coastline, respectively. (3) CECC showed a U-shaped temporal trajectory from 2010 to 2025, declining before 2016 and increasing thereafter, suggesting a shift in the balance between coastal development and ecological management. (4) The PACR framework identified southern Qingdao, northern Weifang, and eastern Rizhao as high-priority restoration areas, whereas the Yellow River Delta and other ecologically intact coastal zones showed relatively low restoration priorities. This study provides a spatially explicit decision-support framework for optimizing coastline restoration prioritization under occupation-compensation balance policies, offering new insights into ecosystem-based coastal management and climate-resilient shoreline governance.