Grid-based Coastal Vulnerability Assessment in Small Island Communities Using Land-use and Habitats for Improved Adaptative Management and Governance

Small island communities face disproportionate climate risks, yet most coastal vulnerability assessments treat ecosystem services as static features, missing the dynamic habitat changes that fundamentally alter coastal protective capacity. We present an operational framework that integrates temporal land-use change and natural habitat dynamics directly into the Coastal Vulnerability Index (CVI) and quantify ecosystem service contributions to coastal risk outcomes. The study was benchmarked in the Siargao Island Protected Landscape and Seascape (SIPLAS), Philippines, where we applied across 418 coastal grids, individual parameters, habitat, and CVI risk ratings, treating coastal ecosystems as protective features, as opposed to vulnerability-amplifying built-up and barren land. Between 2015 and 2020, the built-up area expanded by 124%, while mangroves, corals, and seagrass increased by 34%, 121%, and 56%, respectively, generating an estimated 138–291 million USD per year in ecosystem services, but concentrated away from dense settlements. Mean CVI rose from 14.08 to 14.66, and the share of High and Very High grids increased from 41% to 47%, with 140 grids worsening, 77 improving, and Very High grids showing 99% persistence, indicating vulnerability lock-in. Change-based analysis shows that habitat risk transitions explain 87.4% of the variance in CVI change; each unit of habitat degradation increases CVI by about 2.25 points, making transitions stronger predictors of vulnerability than static habitat states. The framework provides a transparent, data-light tool for small-island governments to prioritize proactive habitat protection and nature-based solutions over costly grey infrastructure in coastal adaptation planning.