A cost‒benefit synergistic framework for balancing ecological importance and vulnerability in island conservation

Islands face significant challenges in prioritizing conservation areas and developing adaption policies under the dual impacts of climate change and human activities. Island conservation has evolved from an early emphasis on safeguarding endemic species and habitats toward a more integrated approach that also considers climate resilience, ecosystem integrity, and human well-being. This study focuses on Hainan Island, considering its vulnerabilities and ecological features. We identified conservation priority areas and corridors under different scenarios and targets using Marxan model and circuit theory. The results indicated that as the conservation targets increased from 10% to 100%, the fragmentation of priority conservation areas showed an initial increasing trend followed by a decreasing trend. In addition, conservation costs increased monotonically, while efficiency followed a logarithmic growth pattern. Therefore, we identified a ‘surface-line-point’ conservation pattern derived from a synergistic scenario at the 50% target, which offered the optimal balance between expenditure and efficiency in safeguarding key ecological functions. It enables policymakers to visualize trade-offs between ecological conservation and climate adaptation, supporting the strategic incorporation of evidence-based natural and engineering solutions. This study offers a decision-support tool for islands, supporting efforts to align ecological priorities with the Sustainable Development Goals.