The SIDS are located in the tropical ocean basins of the world ocean between 30° S–30° N (Fig. 1). The SIDS EEZs cover 8 % of the global ocean, and 15 % of the global tropical ocean (30° S–30° N). For the different basins, the SIDS EEZs cover 18 % of the tropical Pacific Ocean, 8 % of the tropical Atlantic Ocean, and 12 % of the tropical Indian Ocean (Fig. 1). SIDS are widely recognized as stewards of the ocean and leading advocates for ocean sustainability and environmental governance (Hassanali et al., 2026; Keo and Yoona, 2022; Martyr-Koller et al., 2021; Vousdoukas et al., 2023). SIDS have become influential voices in global negotiations on marine conservation, fisheries, and ocean sustainability, as they can shape outcomes through coalition-building, scientific expertise, diplomacy, and normative leadership (Haas et al., 2023; Saddington, 2023). Notably, they played an important role in securing the 1.5 °C degree limit within the Paris Agreement and championed an ambitious BBNJ Agreement (Hassanali et al., 2026). SIDS have also been recognised as Large Ocean States because their identities, economies, and governance are defined more by ocean space than by land (Hume et al., 2021), positioning them as key actors in ocean governance. For example, SIDS are emerging as important innovators in ocean governance, developing integrated approaches that link conservation and biodiversity, fisheries, tourism, and economic development, and hence they play a growing role in shaping sustainable ocean management practices at both national and international scales (Singh et al., 2025). Particularly, SIDS are actively engaged in transformative ocean governance involving key principles such as biodiversity, inclusivity, equity, adaptability, and cross-sectoral coordination, which are key for addressing the interconnected environmental, social, and economic challenges (Lombard et al., 2023). Spalding et al. (2023) argued that strengthening the role of SIDS is essential for more equitable and effective global ocean governance systems as they are well positioned to activate evidence-based and context-specific solutions to ocean-sustainability challenges.

Marine ecosystems hold globally 43 biodiversity hotspots

Geographic areas that are exceptionally rich in species, ecologically distinct and/or show high endemism (species occurring in that defined geographic area and nowhere else) are broadly recognised as biodiversity hotspots and prioritised for conservation (Costello et al., 2023).

Transformations in the world's ocean due to climate change will disproportionately affect SIDS. Sea level rise, ocean warming, ocean acidification, and declining warm-water coral reefs will all have adverse impacts on SIDS, who often also have the lowest adaptive capacity (IPCC, 2019). Amongst those, sea-level rise constitutes one of the most significant challenges facing SIDS. Due to the concentration of populations, economic activities, and critical infrastructure within coastal zones, SIDS are disproportionately exposed to the impacts of rising sea levels (Martyr-Koller et al., 2021). Beyond its physical and socioeconomic consequences, sea level rise also raises complex legal and political questions concerning statehood, sovereignty, and the right to self-determination, particularly for low-lying island nations whose territories may become increasingly uninhabitable or submerged (Green and Wewerinke-Singh, 2025; Labh, 2025). Accounting for changes of sea level over the period 1999–2025, 65 % of all SIDS EEZs are directly exposed to sea level acceleration, and 50 % in the Atlantic Ocean, 76 % in the Pacific Ocean, and 33 % in the Indian Ocean (Fig. 1). Adaptation to sea-level rise is therefore a critical component of climate resilience strategies in SIDS.

However, the effectiveness of adaptation measures is constrained by a range of financial, institutional, technical, and geographical barriers (Thomas and Theokritoff, 2024; Robinson et al., 2023). Furthermore, evidence suggests that adaptation limits are likely to be reached in many SIDS under global warming scenarios exceeding 1.5 °C, thereby increasing the risk of irreversible losses and damages (Martyr-Koller et al., 2021). SIDS are hence sentinels for implications of planetary warming, the processes destabilising their coasts today such as from sea level rise are the same processes that will affect low-lying and densely populated coastal areas worldwide. Also, sea-level rise in SIDS raises fundamental questions about adaptation limits, relocation, and even sovereignty, making them key sites where the future of climate governance is already being negotiated in practice.

SIDS are highly dependent on food from aquatic environments (often also named “blue food”) for food security, employment, and state revenue, with fisheries forming a core pillar of national economies and diets (Bell et al., 2021; Teneva et al., 2023). For example, fishing for tuna plays a vital role in the economic development and food security of most of the 22 Pacific Island countries and territories (FFA, 2023; Bell et al., 2021), and more than 95 % of all tuna caught from their EEZs comes from almost half (10, from which 9 implemented cooperative management) of the Pacific SIDS, where access fees paid by industrial fishing fleets provide an average of 37 % (range = 4 %–84 %) of their government revenue (excluding grants) (Bell et al., 2021). From 2020 to 2022, the annual value of the tuna catch taken in Forum Fisheries Agency waters (17 members; https://www.ffa.int/, last access: 17 June 2026) averaged USD 2.6 billion (FFA, 2023). Hence, changes in marine biodiversity and fish stocks are not just ecological loss, but become a direct precursor for inducing food system stress. SIDS have currently overfished their waters to the extent that their current catch is just under 50 % of the maximum catch potential, which results in direct and indirect food security impacts, including losses in healthy, varied and nutrient-rich food, revenues, incomes and economic impacts in SIDS (Sumaila et al., 2013). For the year 2021, 63 % of 30 SIDS

No data available for Singapore, Niue, Cook Islands, Belize, Saint Kitts and Nevis, Dominica, Saint Lucia, Saint Vincent and the Grenadines, Grenada.

Ocean warming is driven by global warming and has reached record values globally in 2025 (WMO, 2026). For coral reefs, ocean warming disrupts the coral-algae symbiosis, leading to coral bleaching and metabolic stress, which in turn reduce growth and reproduction, increase disease susceptibility, and decrease calcification and reef-building capacity (IPCC, 2023; Pfab et al., 2024; Hughes et al., 2020, 2017). But ocean warming can induce also other implications such as sea level rise, ocean circulation change, increased frequency and intensity of marine heatwaves, reducing carbon uptake capacity, fuel tropical storms, changes in marine ecosystem structure and species distributions, and impacts on fisheries and coastal communities (Cheng et al., 2022). Ocean warming is widespread in the tropical ocean (Pan et al., 2026), and approximately 7 % of all SIDS EEZs are exposed to rapid ocean warming as estimated over the period 1960–2025 (Fig. 2).

Globally, coral reef ecosystems are among the most biologically diverse and economically important marine habitats (Bohorquez et al., 2025). They support an estimated 25 % of all marine species and provide hundreds of billions of dollars annually in goods and services, including coastal protection, fisheries, tourism, and medicine, among other benefits (Beck et al., 2018; Costanza et al., 1997; Spalding et al., 2017; Teh et al., 2013). Beyond their economic value, coral reefs also hold subsistence, cultural and spiritual significance for many islands communities (Cramer et al., 2022; Robles-Zavala and Chang Reynoso, 2018). Climate change, together with pollution and overexploitation, now represents an existential threat to coral reefs (Bhuyan et al., 2026; Bohorquez et al., 2025; Pearce-Kelly et al., 2025), and repeated thermal stress drives widespread bleaching, mortality, and long-term loss of ecosystem function (IPCC, 2019; Hughes et al., 2020). Reefs are currently undergoing rapid global-scale ecological reorganisation, threatening their role as key marine biodiversity reservoirs (Tebbett et al., 2023). Approximately 28 % of the EEZ area of SIDS contains coral reefs classified as vulnerable, endangered or critically endangered, and which amounts to 27 % in the Pacific, 41 % in the Atlantic, and 22 % in the Indian ocean SIDS EEZ areas (Fig. 2).

Between January 2023 and September 2025, 84.4 % of the world's coral reefs have experienced bleaching-level heat stress, exceeding the previous mass bleaching of 68.2 % during 2014–2017 (Lévy et al., 2026). Approximately 25 % of vulnerable, endangered or critically endangered coral reefs

In the IUCN Red List framework, Vulnerable, Endangered and Critically Endangered represent increasing levels of extinction risk, from high to very high and extremely high risk of extinction in the wild, respectively. Source: https://www.iucnredlist.org/ (last access: 17 July 2026).

Coral reef tourism is a critical ecosystem service, and very high-value reefs in monetary and visitor terms are found in most coral reef jurisdictions, which provides an important incentive for sustainable reef management (Spalding et al., 2017). For 30 % of the world's reefs that are of value in the tourism sector, a total value of nearly USD 36 billion per year has been estimated related to on-reef (e.g., indirect benefits such as the provision of sandy beaches, sheltered water, food and attractive views) and reef adjacent value (in-water activities such as diving and snorkelling) (Spalding et al., 2017). Globally, SIDS are the most economically dependent states on coral reefs for tourism and fisheries (Bartelet et al., 2024; Teelucksingh et al., 2013). Coral reefs also represent favourable locations for luxury resorts, which play a significant role in the economic development of SIDS (de-Miguel-Molina et al., 2014).

In terms of tourism, coral reefs can account for over 20 % of GDP in some SIDS (OECD, 2020). For the Maldives, Palau, the Turks and Caicos Islands, and the British Virgin Islands in particular, they underpin more than one third of total tourism value (Spalding et al., 2017). In many cases, tourism represents one of the few income sources given the limited availability of alternative livelihoods (Chaijaroen, 2023). Coral reefs also provide coastal protection of tourism infrastructure as they act as natural breakwaters, reducing wave energy and protecting beaches, hotels, resorts, and other coastal infrastructure from erosion and storm damage, which is particularly important for low-lying island nations vulnerable to sea-level rise and extreme weather (Vousdoukas et al., 2023; Ferrario et al., 2014).

SIDS are faced with a multitude of disasters, including high vulnerability to cyclones, floods, droughts, earthquakes, tsunamis, and sea-level rise. The disaster mortality rate across SIDS is more than double the global average (IPCC, 2023) associated with high hazard frequency, high concentrations of population in low elevation coastal zones, geographical isolation and lack of economic scale. At the same time, and as of 2023, only 38 % of SIDS reported having multi-hazard early warning systems in place (UNDRR, 2025). According to the Emergency Events Database (EM-DAT), a total of 393 natural hazard-related disasters had been recorded in 2024, which caused 16 753 fatalities, and affected 167.2 million people (CRED, 2025). Regarding tropical cyclones, Hurricane Beryl in 2024, the earliest Category 5 hurricane on record, caused over USD 1 billion in damages across Grenada and Jamaica (Bevan et al., 2025). In the South-West Indian Ocean, Cyclone Belal and Cyclone Hidaya severely affected island nations, such as Réunion, Mauritius and Madagascar, resulting in fatalities, large-scale displacement, and substantial infrastructure damage (CRED, 2025). In 2025, 358 natural hazard-related disasters have been recorded by EM-DAT, which resulted in 16 607 fatalities, affected 110.2 million people, and caused USD 170 billion in economic losses (Delforge et al., 2026). During this year, Hurricane Melissa, for example, affected approximately 7.6 million people across Jamaica Haiti, Cuba, and the Dominican Republic. Jamaica alone, where Hurricane Melissa made landfall as a category 5 hurricane, experienced an estimated USD 10 billion in losses, one of the highest recorded in 2025 (Delforge et al., 2026). Based on available records, cumulative tropical cyclone damage exceeded 50 % of national GDP in approximately 40 % of SIDS with available data, although data availability and record length vary among countries (1903–2026) (Fig. 3).

Key drivers of tropical cyclone intensification include ocean temperature, vertical wind shear and dry air entrainment, with the intensification potential dictated by complex causal chains (Emanuel et al., 2004). These constraints can influence the way the critical thermodynamic interface for ocean-storm interaction evolves, and thus modifies storm intensity (Dzwonkowski et al., 2020). Tropical cyclones intensify by extracting energy from the warm ocean surface with the upper ocean thermal structure critical for their development, and ocean temperature over 26 °C generally regarded a necessary condition (e.g. Gray, 1968). Warm ocean temperatures increase the potential intensity of a tropical cyclone and lead to its intensification (e.g., Dzwonkowski et al., 2020; Jaimes et al., 2015, 2016; Hallam et al., 2019). Tropical Cyclone Heat Potential (TCHP) quantifies the integrated heat content of the upper ocean above the 26 °C isotherm and is widely used as an indicator of the oceanic energy available to support tropical cyclone intensification, as it refers to the subsurface thermal structure as a measure of the potential for cyclone intensification (Momin et al., 2021; Sasaki and Motoi, 2022). Rising ocean temperatures are leading to increases in tropical cyclone intensity (Hallam et al., 2021) and marine heatwaves have shown to increase tropical cyclone intensity, and precipitation richer cyclone conditions (Choi et al., 2024). IPCC (2021) has assessed that the global proportion of Category 3–5 tropical cyclones (TC) has increased over the past four decades, and some studies have linked this increase to an increase in THCP (Liu and Chan, 2022; Song et al., 2021; Wada and Chan, 2021), together with other potential drivers (Wada and Yanase, 2024). Over the period 1960 to 2025, approximately 56 % of the SIDS EEZ areas have experienced above global average increases in tropical cyclone heat potential (Fig. 3), indicating increase in upper-ocean heat availability for tropical cyclone intensification. For the EEZ SIDS areas in the Pacific Ocean, 73 % are exposed to rapid increase in tropical cyclone heat potential, and 32 % in the Atlantic, while EEZs of SIDS in the Indian Ocean are less exposed to this change (1 %) (Fig. 3). There is an increasing number of Category 4 tropical cyclones observed in recent years (Fig. 3), together with high cumulative damages relative to national GDP. Based on available country records, 10 SIDS (Jamaica, St Kitts and Nevis, Grenada, Dominica, Belize, Samoa, Bahamas, Antigua and Barbuda, Vanuatu, and Tonga) have experienced cumulative damages exceeding 50 % of Gross Domestic Product (GDP), although the length of the historical record varies among countries.

As discussed above, increasing tropical cyclone heat potential can intensify tropical cyclones, which in turn enhances storm surge potential through stronger winds and lower atmospheric pressure (Balaguru et al., 2024; Guo and Tan, 2026). For SIDS, storm surge represents one of the most destructive impacts of tropical cyclones, as intensified storms can generate extreme coastal water levels that rapidly inundate densely populated low-lying coastal zones (IPCC, 2023; Irish et al., 2011; Vousdoukas et al., 2023). In addition, rising ocean heat content not only increases tropical cyclone intensity but also contributes to higher baseline sea levels through thermal expansion, amplifying storm surge impacts when cyclones make landfall (Vousdoukas et al., 2023). In SIDS, storm surge impacts are increasingly compounded by heavy rainfall and rising mean sea level, leading to more frequent and severe coastal flooding events during tropical cyclones (Grimley et al., 2024; IPCC, 2023). Nearly 20 % of assessed SIDS (7 out of 40) have experienced tropical cyclone–induced storm surges exceeding 3 m based on historical records spanning 1961–2012 (Fig. 3).

Mangroves provide a critical form of natural coastal protection as they reduce waves and storm surges, and serve as a first line of defence against flooding and erosion (Gedan et al., 2011; Sandi et al., 2018; Thampanya et al., 2006; Krauss et al., 2014). Globally, mangroves provide flood protection benefits exceeding USD 65 billion per year, and if mangroves were lost, 15 million more people would be flooded annually across the world (Menéndez et al., 2020). This demonstrates that the essential value of mangroves as natural coastal defences at global, national, and local scales and can provide incentives for mangrove conservation and restoration in development, climate adaptation, disaster risk reduction, and insurance (Menéndez et al., 2020). Yet, mangroves have experienced significant losses over the last decades with a global loss of 11.8 % since 1970 (Lévy et al., 2026; RAMSAR et al., 2025). The mangrove coastal protection annual expected benefit exceeds USD 1 million in 18 SIDS.