Ocean change in Small Island Developing States

Small Island Developing States (SIDS) depend fundamentally on the ocean for their societies, economies and livelihoods, yet they are among the regions most exposed to ocean changes. Here we present an ocean narrative that quantifies the environmental, economic and societal dimensions of this exposure using a suite of integrated ocean indicators. Through their Exclusive Economic Zones (EEZs), SIDS cover approximately 8 % of the global ocean and 15 % of the tropical ocean (30° S–30° N), encompassing globally important biodiversity hotspots, including coral reefs, mangroves and seagrasses. At the same time, 65 % of their EEZ area is experiencing accelerated sea-level rise, widespread ocean warming, and 56 % of EEZs exhibit rapid (above-global-average) increases in tropical cyclone heat potential since 1960, which represents the ocean heat available to fuel cyclone intensification. Nearly one-third of the SIDS EEZ area contains coral reefs classified as vulnerable, endangered or critically endangered, and one quarter of these reefs have experienced severe accumulated marine heat stress. Coastal hazards are further illustrated by cumulative tropical cyclone damages exceeding 50 % of national GDP in approximately 40 % of assessed SIDS, while nearly 20 % of assessed SIDS have experienced storm surges exceeding 3 m. Nature-based coastal protection also emerges as a critical component of climate resilience, with mangrove ecosystems for example providing annual avoided damages exceeding USD 1 million in 18 SIDS. This ocean narrative highlights the dual role of SIDS as custodians of globally important marine ecosystems and sentinels of ocean and climate change, and demonstrates the need to integrate ocean data and science, ecosystem health and resilience and climate risk assessment into ocean governance.