Multi-scale ecological zoning of Chinese coastal islands using a three-dimensional landscape framework

As unique geographic units, islands face increasing anthropogenic pressures due to their fragile ecosystems and limited spatial distribution. Traditional 2D landscape analysis often fails to capture the vertical heterogeneity of island topography, vegetation, and buildings, leading to inaccurate ecological assessments. To address this, we developed an innovative 3D landscape assessment and zoning framework. Using 205 inhabited islands across 11 representative coastal counties in China as a case study, we constructed four key 3D indices (human interference index, landscape fragmentation index, the 3D vegetation index and the 3D building index) and applied K-means clustering to classify island functions at macro (county) and micro (island) scales, comparing the results with a 2D perspective. The 3D analysis provides a more accurate assessment, revealing significantly higher levels of anthropogenic disturbance and landscape fragmentation that are systematically underestimated by 2D methods. This led to a critical reclassification: the zoning types of 4 island counties and 12 islands changed. Some areas previously considered moderately developed were re-identified as high-intensity development centers due to their significant building volumes and vertical structures. Our 3D framework offers crucial managerial applications, enabling planners to more accurately diagnose ecological pressures and refine functional zoning. This approach provides a robust scientific basis for adjusting urban planning guidelines, optimizing resource allocation, and developing targeted conservation strategies that account for vertical landscape connectivity. • An innovative 3D landscape framework for island ecological zoning is proposed. • 3D analysis reveals ecological pressures underestimated by 2D methods. • Vertical structural analysis leads to a critical reclassification of island functions. • This provides a more scientific basis for sustainable island spatial planning.