World leaders on Thursday approved the first United Nations declaration on sea level rise, affirming that nations losing land to the ocean will keep their statehood and maritime rights, as a new UN report warned that up to 1.2 billion people could be displaced by 2050.

Championed by small island states, the declaration affirms a “presumption in favour of continued statehood,” including membership of the UN.

Statehood under international law has long rested on a defined territory and a permanent population, leaving low-lying nations facing the prospect that losing their land could mean losing their UN seat, their citizens’ nationality and the vast ocean zones that fund their governments. Kiribati’s territory spans 3.5 million square kilometres of ocean, but just 0.02% of it is land.

The declaration also affirms that maritime zones, once established under the UN Convention on the Law of the Sea, remain stable as coastlines retreat. It commits states to expand early warning systems and risk data, calls for more accessible finance for adaptation, and pledges to protect the rights, livelihoods and cultural heritage of people forced to adapt or move. The political declaration is not legally binding and carries no new money.

Approved without objection at a high-level meeting of the General Assembly in New York, the text now goes to a formal plenary for adoption. Countries agreed to reconvene on the issue before the end of the Assembly’s 84th session.

The United States, which has withdrawn from the Paris Agreement and moved to cut federal ocean research, did not block the text and did not take the floor during the day-long debate.

“Sea level rise is measured in millimetres, but its toll is measured in millions of shattered lives, uprooted communities and stolen futures,” Secretary-General António Guterres told the meeting. “We cannot allow countries and cultures to vanish beneath the waves.”

“The measure of our success today will not be the words we endorse, but the action that will follow,” said Tuvalu Prime Minister Feleti Teo, who told the Assembly he spoke for the “1 billion people living in countries and communities on the front line.”

Record rise

Global sea levels rose a record 5.9 mm in 2024, according to Guterres’s report, which found seas are rising faster than at any point in recorded history and that the rise to date is “essentially irreversible on human timescales.”

“Greenhouse gases billowing from burning fossil fuels are cooking our planet, and the ocean is taking the heat,” Guterres said. The ocean absorbs some 90% of that excess heat.

The 1.2 billion figure, which spans rising seas, flooding, water stress and food insecurity, adds to a broader climate displacement picture in which billions face threats from extreme heat, storms and the loss of habitable land.

“When land disappears and fresh water turns to salt, competition follows and we risk a mass exodus of entire populations,” Guterres said.

The meeting came weeks after a UN report warned that holding warming to 1.5C is no longer possible, with the threshold likely to be crossed by 2030, and that colliding threats from unbalanced ecosystems around the globe could “change the world forever.”

Guterres urged that any overshoot be “as small and short as possible,” adding that “the G20 must lead, and COP31 in Türkiye must deliver.”

Current policies put the world on course for about 2.6C of warming, enough to drive roughly 60 cm of sea-level rise by 2100 and push the West Antarctic and Greenland ice sheets past points of no return.

Crossing those thresholds “would mean the extinction of many small island states, but also a catastrophic reshaping of coastlines around the world, affecting many hundreds of millions of people,” said Bill Hare, chief executive of Climate Analytics.

‘More ocean than land’

Nearly 770 million people, roughly one in ten worldwide, live less than five metres above the high tide line. Without significant adaptation and mitigation, Guterres said, the risks facing coastal cities and communities could increase tenfold by 2100.

“Vanuatu is more ocean than land,” the Pacific nation’s representative told the Assembly. “The sea has always been our highway, our food and our heritage. Today it is also a threat.”

Across the Pacific, where relative sea levels have risen more than twice the global average, the report finds rising seas “are already forcing relocations in Fiji, Vanuatu, the Solomon Islands and elsewhere,” placing “the habitability of entire nations in jeopardy.”

In Saint Vincent and the Grenadines, 85% of the population and more than 90% of critical infrastructure sit on a narrow coastal belt, Prime Minister Godwin Friday said. In Bangladesh, 25 cm of sea-level rise by 2050 could submerge around 4% of the country’s land and upend the lives of some 10 million people, Prime Minister Tarique Rahman said, citing World Bank estimates.

“We do not come to this meeting to observe another country’s emergency,” said Kenya, where nearly a third of the coastline now falls in the highest risk category. “We come because it is already ours.”

“Rising seas are not good for anyone, not for small island developing states, not for low-lying coastal communities, not for major cities,” said General Assembly President Khalilur Rahman. “Including this one right here. The city of New York.”

Seas around New York are projected to rise 1.3 metres by the end of the century, he said, “enough to turn our august assembly hall into a very large wading pool.”

Under a low-likelihood scenario driven by ice-sheet instability in West Antarctica, the IPCC projects seas approaching two metres by 2100. The Thwaites Glacier, nicknamed the “Doomsday Glacier” and larger than England, Wales and Northern Ireland combined, would add 65 cm on its own if it collapsed.

“During storms, the sea is patient,” said the representative of the Kingdom of the Netherlands, whose Caribbean islands face sea-level rise of up to 80 cm by 2100. “It takes a little more each year, and what it takes, it does not easily return. We cannot afford to be patient in return.”

Millions displaced

The populations facing both sea-level rise and extreme heat, in coastal South Asia, sub-Saharan Africa and the low-lying deltas where rivers meet the sea, are where the crisis will be least voluntary and most catastrophic. Across Kolkata, Mumbai and Dhaka, more than 14 million people face immediate risk of losing their homes to permanent inundation.

“Mountainous countries and island states, which contribute least to global emissions, stand as the most acute victims of global climate crisis,” said Nepal’s representative, weeks after flash floods tore through the Himalayan country in August. “This is unjust. This is our moral failure.”

In North Africa’s Nile Delta, saltwater intrusion is contaminating land and freshwater while the same populations face worsening drought and extreme heat.

Ports carry more than 80% of global merchandise trade, Khalilur Rahman noted, and when rising water disrupts them, the effects reach food prices, medicines, jobs and household budgets worldwide. A 2020 study in the Proceedings of the National Academy of Sciences projected that by 2070, extreme heat zones now covering less than 1% of the earth’s land surface could expand to nearly a fifth, placing one in three people outside the climate conditions where humans have thrived for 6,000 years.

“No country is truly beyond the reach of the shoreline,” said Cyprus.

Trillions at risk 

In coastal megacities like Miami, New York and Guangzhou, economic engines that drive trade, finance and millions of jobs, assets valued between $2 trillion and $3.5 trillion face flooding. Globally, coastal infrastructure worth at least $1.8 trillion is at risk.

Developing states need an estimated $310 billion to $365 billion a year for adaptation. In 2023, they received $26 billion.

The Fund for Responding to Loss and Damage holds pledges of $768 million but had received only $321 million as of March 2025. Against projected loss and damage costs of $290 billion to $580 billion a year by 2030, its start-up envelope stands at just $250 million. “I am very frustrated with the, I would say, ridiculous amount that is today in the Loss and Damage fund,” Guterres said.

“The adaptation gap is not a knowledge gap,” Navid Hanif, the UN assistant secretary-general for economic and social affairs, said at the report’s launch. “It’s a financing gap.”

Guterres called for adaptation finance to triple and for the $300 billion annual climate finance goal agreed in 2024 to be a step toward mobilising $1.3 trillion a year by 2035.

“Irreversible loss and damage cannot be concealed within adaptation,” Jamaica said on behalf of the Caribbean Community, calling for support that is “grant based, not another source of debt.”

Kenya urged the UN system, development banks and climate funds “to organize themselves around the speed of the tide, not the pace of their own procurement.”

The report calls for wider use of instruments like catastrophe bonds and regional risk pools, though these were built for sudden shocks, and Cyprus told the Assembly that finance must be “designed for slow onset risks, not only sudden disasters.”

The cost of the gap falls on public services, said Trinidad and Tobago’s representative, noting that money spent on recovery “is always diverted from critical areas such as healthcare, agriculture and defence.”

Data missing as US pull back monitoring

“Africa’s coastlines remain among the least observed on earth,” Kenya’s representative said, urging states to build coastal risk mapping into national planning “so that no new school, road or clinic is built where the data already tells us the sea is coming.”

The report warns that coastal sea levels are often higher than existing assessments show, leaving tens of millions more people at risk than recognised.

In the US, the Trump administration is dismantling the Ocean Observatories Initiative, a $386 million network of more than 900 ocean sensors that has provided continuous real-time data for over a decade.

The administration’s budget proposal described NOAA’s climate programmes as part of a “Green New Scam,” accusing them of efforts to “radicalize students” and spread “baseless environmental alarm.” NOAA’s research arm faces a proposed cut from $656 million to roughly $171 million.

A day before the meeting, European Commission President Ursula von der Leyen and Canadian Prime Minister Mark Carney launched a Global Ocean Alliance to support ocean observation, with more than 30 countries pledging over $250 million, EU Oceans Commissioner Costas Kadis said.

A legal reckoning

While data and financing lag behind, international law is moving in the opposite direction, increasingly recognising the rights of at-risk nations and communities in its highest courts.

“Geography may change. Legal identity must not,” said the Maldives.

“No state will be forced to turn off their nameplate without their consent due to sea level rise,” said Liechtenstein, while Saint Kitts and Nevis told the Assembly that “a nation’s legal personality cannot depend on a climate it did not destabilize.”

The United Kingdom announced it would now start from the position of continuing to recognise a state’s statehood even if it loses some or all of its land to the sea. Australia noted the principle first appeared in a legally binding treaty it signed with Tuvalu, and is now written into the UN declaration.

In May 2024, the International Tribunal for the Law of the Sea ruled unanimously that greenhouse gas emissions constitute marine pollution that states must prevent, reduce and control. In July 2025, the International Court of Justice found unanimously that both state action and inaction on climate change can breach international law. Both cases were brought by small island states.

“People’s rights do not disappear because their homes do,” Guterres said.

The ICJ found that states’ climate obligations reach well beyond the Paris Agreement into customary and human rights law, and that breaching them can require states to stop the harmful conduct and make full reparation. Advisory opinions are not binding in themselves, but they carry the court’s authority on what existing law requires.

In May, the General Assembly voted 141 to 8 to welcome the opinion, with the United States, Saudi Arabia and Russia among those voting against. During those talks, fossil fuel-producing states pushed to cast the UN climate treaties as the only framework governing climate action, the same argument the court had already rejected.

Saudi Arabia, which joined Thursday’s consensus, said it had shown “flexibility” on references to the ICJ opinion during negotiations but that its legal position “remains the same,” rejecting any attempt “to impose anything on states outside of existing frameworks.”

Russia said states’ obligations are “codified in specialized international legal instruments” and should be discussed only “at the specific relevant platform to avoid watering down norms.”

“Vanuatu led the call for the ICJ advisory opinion and the court answered unanimously,” its representative said. “States have binding obligations to prevent climate harm, to cooperate and to protect the human rights that sea level rise affects.”

Turkey, host of the COP31 climate summit in Antalya in November, said the reasons keeping it outside the UN Convention on the Law of the Sea, the treaty anchoring the declaration’s maritime protections, “remain valid.”

“Today we are applauded for adopting the resolution,” said Cabo Verde’s Prime Minister Francisco Carvalho, who co-led the negotiations with Australia. “Tomorrow we will be judged by our ability to implement it.”

Image Credits: Unsplash/Ernests Vaga, Felix Sassmannshausen/Canva benkrut/anmuelle via Getty Images, Giorgia Galletoni .