OCEAN STATE IN 2026

Editions
2026 2025
The second edition of the Starfish Barometer reaffirms that the Ocean is undergoing rapid, alarming and accelerating changes, marked by record-breaking heat, consequent rising seas, widespread species decline, and essential ecosystems such as coral reefs facing critical levels of threats. These findings reinforce the urgent need to protect and restore the health of our Ocean.
Protection effortsHuman Pressures
Protection effortsHuman Pressures

Global mean sea level and ocean warming are rising at an accelerating rate

Global mean sea-level rise is a consequence of Ocean warming and land ice melt. While global mean sea level rise was estimated at 2.6±0.3 mm/y over the period 1993 to 2011, this rate has increased to 4.2±0.3 mm/y over the period 2012–2025, consistent with an acceleration in sea-level rise over the last 30 years. Global mean Ocean warming is also accelerating since 1960 and reached record values in 2025. In addition to these long-term trends, recent years have been consecutively marked by particularly high values. In 2025, global mean temperatures at the sea surface reached their third highest levels on record, at 0.49 ◦C above the 1981–2010 baseline slightly below the peaks observed in 2023 and 2024, with 20% of the Global Ocean experiencing strong marine heatwave conditions in June 2025. Warming is a climate change stressor to marine ecosystems that adds to other climate change stressors such as changes in salinity, deoxygenation, and acidification. About 25% of the top 1,000 m of the Ocean is now affected by more than two climate change stressors simultaneously.

Global sea ice extent reached its second lowest annual maximum at 32.1 million km² since 1982

Sea ice is frozen seawater that forms in autumn and winter in both polar Ocean basins and progressively melts in spring and summer. It is important because it helps regulate Earth’s climate and supports polar ecosystems. With climate change, the maximum extent reached by sea ice in winter continues to rapidly shrink in the Arctic, and since 2015 also in the Antarctic. Annual maximum sea ice extent reached 14.3 million km2 in March 2025 in the Arctic and 17.8 million km2 in September 2025 in the Antarctic, adding up (asynchronous sum) to 32.1 million km2 taken together. The Annual minimum was 4.6 million km2 in September 2025 in the Arctic and 2.0 million km2 in March 2025 in the Antarctic. This is the fourth consecutive year that Antarctic sea ice has reached a minimum below 2.0 million km2. Declining sea ice is increasing the accessibility of trans-arctic shipping routes.

1,685 marine species are now threatened, with deterioration in conservation status

As of the most recent update (April 2026), 1,685 (8.6%) of the 19,508 marine species assessed by the International Union for Conservation of Nature worldwide are classified as threatened with extinction on their Red List. This indicator provides a broad signal of the status of assessed marine biodiversity, although it also reflects the evolving coverage and completeness of species assessments over time. Compared with the value reported in the previous edition of the Barometer, the current assessment includes eight additional threatened marine species. Of the threatened species, 293 are classified as Critically Endangered, 660 as Endangered, and 732 as Vulnerable. This corresponds to a deterioration in conservation status for 30 species since last year. Population trends reinforce this assessment: 1,224 threatened species are experiencing population declines, 13 more than last year, while only 28 species show increasing populations (one fewer than in 2024). Beyond extinction risk, the IUCN Red List also reports 1,631 threats to ecosystems such as invasive and other problematic species, genes and diseases affecting marine ecosystems, further undermining ecosystem stability and resilience.

84.4% of coral reefs experienced heat stress severe enough to cause bleaching

Warm-water coral reefs are among the most diverse and valuable ecosystems on Earth. They occupy nearly 0.2% of the global seafloor, support at least 25% of all marine species, and underpin coastal protection, food security, livelihoods, cultural values and human wellbeing for hundreds of millions of people worldwide. Climate change now represents an existential threat to coral reefs, and repeated thermal stress drives widespread bleaching, mortality, and long-term loss of ecosystem function. Between January 2023 and September 2025, 84.4% of the world’s coral reefs have experienced bleaching level heat stress, exceeding the previous global record of 68.2% during 2014–2017 and far surpassing the 1998 and 2010 mass bleaching episodes. Coral reef degradation is also influenced by additional stressors such as eutrophication, acidification, and overfishing, which can act in synergy with climate change. All wetland ecosystems have been losing surface area since 1970: coral reefs (-26.4%) but also mangroves (-11.8%), salt marshes (-14%), kelp forests (-48.1%), and seagrass (-16.3%).