The United Nations General Assembly has adopted its first declaration on sea level rise, affirming that countries threatened by rising oceans do not automatically lose their statehood if their territory becomes submerged.

The four-page declaration, adopted on September 24, 2026, at a high-level meeting alongside the 81st session of the UN General Assembly in New York, also calls for stronger action to protect vulnerable coastal communities.

It is the first time UN member states, including the United States, have agreed on a common declaration addressing sea level rise.

The agreement is particularly significant for small island developing states (SIDS) and low-lying coastal countries, which face growing threats to their land, infrastructure and livelihoods as global temperatures rise.

According to a report presented by UN Secretary-General António Guterres, global mean sea level rose by 5.9 millimetres in 2024, reaching a record high, primarily because of exceptional ocean warming.

Sea levels remained close to that record in 2025, following a sharp increase between 2023 and 2024. The rate of sea level rise is expected to increase through 2050 because of warming already locked into the climate system, the report said.

Island nations and the question of statehood

One of the declaration's central provisions concerns the legal status of island nations whose territories are threatened by rising seas.

Countries such as Tuvalu and the Marshall Islands face the prospect of extensive inundation over the coming century, raising questions about what happens to a sovereign state if its territory becomes uninhabitable or disappears beneath the ocean.

The declaration affirms that the physical disappearance of territory or changes to a coastline caused by sea level rise do not automatically result in the loss of statehood. This means that the continued existence of a country under international law would not necessarily depend on its territory remaining above water.

The declaration also recognises the efforts of small island developing states, which have raised concerns about sea level rise for more than three decades. It refers to the 1989 Malé Declaration on global warming and sea level rise, as well as subsequent agreements adopted by Pacific Islands Forum leaders in 2021 and 2023 on preserving maritime zones and the continuity of statehood.

The Alliance of Small Island States (AOSIS) adopted related declarations on sea level rise and statehood in 2021 and 2024.

The UN declaration follows a July 2025 advisory opinion by the International Court of Justice (ICJ), which stated that a country would not necessarily lose its statehood if one of the elements traditionally associated with statehood ceased to exist. The court also addressed the importance of respecting established boundaries under international law.

The General Assembly declaration calls for stability in maritime zones despite physical changes to coastlines.

It states that countries can maintain maritime zones established under the UN Convention on the Law of the Sea (UNCLOS) as sea levels rise, while retaining the right to update them.

This is particularly important for island nations because maritime zones determine rights over ocean resources and activities. The UN had warned that without urgent adaptation measures, up to 1.2 billion people could be displaced by 2050.

Calls for early warning systems and adaptation finance

The declaration also addresses the wider threat that rising seas pose to coastal populations, infrastructure and livelihoods. Around 770 million people worldwide live less than five metres above the high-tide line, according to a UN report on sea level rise and human rights.

Without significant efforts to reduce emissions and adapt to rising seas, the risks facing coastal cities and communities could increase tenfold by 2100, the report warned.

The declaration calls for stronger anticipatory action, including multi-hazard early warning systems, and for climate-related risk assessments to be incorporated into planning and decision-making.

It also urges greater international cooperation to provide financial, technical and policy support to developing countries, particularly small island developing states and least developed countries.

The declaration calls for increased funding to support local responses to sea level rise.

It identifies nature-based measures, including the protection and restoration of mangroves, kelp forests and seagrass meadows, as ways to help coastal communities adapt.

Such ecosystems can reduce the impact of coastal hazards while providing other environmental benefits.

The declaration also calls for sea level rise projections to be taken into account when planning, constructing and maintaining critical coastal infrastructure, including ports, energy and transport systems, water supplies and healthcare facilities.

Other measures identified include coastal protection, land reclamation and raising land levels.

‘Only strong climate action can stop sea levels rising’

Despite the agreement, the declaration itself cannot prevent further sea level rise, said Surangel Whipps Jr, President of Palau and Chair of AOSIS.

"Only strong climate action can do that. Sea level rise is a direct result of climate change. Every fraction of a degree of warming means more sea level rise is locked in," he said in an AOSIS statement.

The declaration establishes a common international position on the legal and practical challenges posed by rising seas. Its calls for adaptation, financial support and stronger climate action will, however, depend on implementation by individual countries and international institutions.

State of Climate: Rising temperatures

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