Introduction
1. Pursuant to the request made by the General Assembly, in its decision 78/558, for the Secretary-General to prepare a report on challenges related to sea level rise and on ways and approaches to address sea level rise, the 39 small island developing States (SIDS) of the Alliance of Small Island States (AOSIS) submits this document. It highlights how small island developing states (SIDS) have addressed these challenges through coordinated international action in multilateral frameworks and processes. Individual SIDS may provide separate submissions detailing their specific national and regional circumstances.

Ways and approaches to address the challenges of sea level rise

Address the root cause
2. The most fundamental response to sea-level rise is to strengthen global efforts to address climate change through deep, rapid, and sustained reductions in greenhouse gas emissions. The objective must remain limiting the global average temperature increase to 1.5°C above pre-industrial levels. As affirmed by the International Court of Justice in its Advisory Opinion of July 2025, this 1.5°C limit constitutes a legally binding obligation under the Paris Agreement.

3. Alongside more than three decades of advocacy for stronger mitigation action, AOSIS has consistently called for anticipatory measures to address the impacts of sea-level rise. These include investments in early warning systems and financing for adaptation measures such as resilient infrastructure, coastal defenses, and ecosystem-based approaches. Nevertheless, there are limits to adaptation. Sea-level rise will lead to irreversible losses—including of assets, ecosystems, cultural heritage, and livelihoods—and may cause the displacement of people and, in some cases, the loss of land territory.

Addressing the impacts through international law
4. Since the 1989 Small States Conference on Sea Level Rise in the Maldives, SIDS have been at the forefront of the development and application of international law as it relates to the climate crisis and sea level rise.

5. On two issues—stability of maritime zones and continuity of statehood—SIDS have long been clear in their interpretation of international law and engaged consistently with the General Assembly, the Sixth Committee, the International Law Commission and the International Court of Justice on these topics.

6. On the stability of maritime zones, SIDS have consistently affirmed that maritime zones, as established and notified to the Secretary-General of the United Nations in accordance with the United Nations Convention on the Law of the Sea (UNCLOS), and the rights and entitlements that flow from them, shall continue to apply, without reduction, notwithstanding any physical changes connected to climate change-related sea-level rise.

7. On statehood, SIDS have been clear that there is no existential threat to our statehood from sea-level rise. We must not conflate the physical reality of land territory becoming submerged, with the legal rules concerning statehood and sovereignty, including permanent sovereignty over natural resources.

8. SIDS leaders have declared upon these two issues through state practice and multilateral engagements, including through the adoption of the AOSIS Leaders Declaration 2021, the AOSIS Leaders Declaration on Sea-Level Rise and Statehood 2024, and our written and oral submissions to the International Court of Justice (ICJ).

9. Engaging in the work of the International Law Commission (ILC) on sea level rise has also contributed to the development of our collective understanding of the relevant international law rules. In line with SIDS interpretation of international law on this issue, the ILC reaffirmed that there is no requirement under UNCLOS for States to update baselines, geographic coordinates, charts or outer limits once duly deposited with the Secretary-General in accordance with the Convention—a concrete step towards legal clarity on this issue by preserving legal stability, security, certainty and predictability.

10. Moreover, in 2023, over 130 countries co-sponsored a historic UN General Assembly resolution calling on the International Court of Justice (ICJ) to issue an advisory opinion that clarifies States’ legal obligations in respect of climate change. On 23 July 2025, the ICJ delivered a historic landmark advisory opinion that further supports the fundamental principles and understanding of international law articulated by AOSIS with respect to the stability of maritime zones and continuity of statehood.

11. The ICJ Advisory Opinion affirmed that sea-level rise cannot invalidate existing maritime baselines and entitlements, holding that States parties to UNCLOS are under no obligation to update charts or lists of geographical coordinates once these have been duly established in conformity with the Convention, notwithstanding physical changes resulting from climate-related sea level rise.

12. The Court further recognized that once a State is established, the disappearance of one of its constituent elements would not necessarily entail the loss of its statehood.

13. Of further importance, amid the climate crisis and climate change-related sea level rise, the Opinion also affirmed that the 1.5°C threshold is the agreed primary temperature goal for limiting the global average temperature increase under the Paris Agreement, based on its provisions, subsequent decisions of its governing bodies, and as a reflection of the no harm principle. It further articulated that the submission of NDCs must represent parties’ highest possible ambition to realize the objective of the agreement, noting that NDCs will vary depending on historical GHG emissions, and level of development and national circumstances.

14. As we continue to navigate the legal complexities of addressing climate change and sea level rise, it is critical to note that the Opinion underscores that States have a customary legal obligation to cooperate in addressing climate change. It is therefore critical for the international community to take concrete steps to ensure that the clarity provided on our international commitments and obligations as it relates to climate change, sea level rise and statehood must now translate into actions and solutions across every level — including negotiations under the UNFCCC and Paris Agreement, implementation of national climate policies, and interpretation of rights and obligations in courts around the world.

Conclusion
15. Addressing the challenges posed by sea level rise requires States to fulfil their duty to cooperate under international law—a duty the ICJ Advisory Opinion of July 2025 affirmed as a binding customary obligation. This duty encompasses cooperation in mitigating climate change through rapid emissions reductions, supporting adaptation in vulnerable developing States, providing adequate and accessible climate finance, and developing coherent legal frameworks to address unprecedented questions of statehood, maritime zones, and human mobility.

16. The challenges posed by sea level rise intersect with multiple areas of international law—the UNFCCC and Paris Agreement, UNCLOS, international human rights law, and other frameworks. Coherent and complementary approaches across these instruments are essential to address the multifaceted impacts of sea level rise. The United Nations system, including the General Assembly, specialized agencies, and treaty bodies, must play a central role in translating legal principles into concrete implementation. Regional and sub-regional mechanisms also provide vital, context-specific responses tailored to geographical and cultural circumstances.

17. Effective responses to sea level rise depend on sustained multilateral engagement and the collective commitment of all States to uphold all of their international legal obligations.