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Alyssa Chen

For low-lying Pacific island states such as Tuvalu and Kiribati, rising sea levels are not just an existential crisis but also one that calls into question the very foundations of statehood.
At the heart of this lies a contentious question: should maritime boundaries shift with changing coastlines, or should they be frozen in place?
The answer carries profound implications not only for the survival of vulnerable islands but also for the rest of the world.
Some analysts have argued that China should position itself as both a legal advocate and technical partner for Pacific nations to offer tangible support – such as surveying expertise, coastal protection technology and advocacy for fixed maritime boundaries.


They said such support could not only help vulnerable states survive but could also advance Beijing’s strategic interests and align with its South China Sea claims.
Projections from Nasa in 2024 showed that sea levels in the Pacific would rise by an average of 15cm (6 inches) over the next three decades.
Beyond the immediate physical threat, shrinking coastlines also pose a fundamental challenge to the 1982 UN Convention on the Law of the Sea (Unclos).
Maritime zones are measured from coastal baselines tied to the physical low-water line. These include territorial seas, which extend 12 nautical miles (22km) from the coast, and exclusive economic zones, which can cover 200 nautical miles.
Such zones grant coastal states exclusive sovereign rights to explore, exploit and manage natural resources ranging from fish stocks to minerals and offshore energy.
However, under Unclos, a land feature must be able to “sustain human habitation or economic life of its own” to have an exclusive economic zone.
If rising seas severely undermine an island’s freshwater supplies, habitability or capacity to sustain an economic life of its own, this could raise questions about how the feature should be classified under Article 121 of Unclos, according to Chen Yitong, an associate professor of international law at the Ocean University of China.
“This could affect the maritime entitlements generated by the feature and may also have implications for baselines or for pending maritime delimitation where the feature is relevant,” Chen said.
“It should not, however, be taken to mean that maritime boundaries already established by treaty or other applicable international legal means can be reopened.”
The legal dimension
“The major legal obstacle [to keeping existing boundaries] is an adjustment of the long-standing legal rule that baselines are ambulatory, which means they can move and be adjusted over time,” said Donald Rothwell, a professor of international law at the Australian National University.
“That rule is reflected in state practice and not in the precise rules of the 1982 United Nations Convention on the Law of the Sea.”




The fallout from discussions about how rising sea levels should be reflected in maritime law reaches far beyond the South Pacific.
“If a coastal country claims its features are full-fledged islands that generate full maritime rights, talks on rising sea levels protect and maintain those features’ surrounding zones and maritime rights will make a significant difference on their claims,” said Chen Chen-Ju, a professor specialising in the law of the sea at National Chengchi University in Taiwan.
Beijing claims sovereignty over almost all islands and reefs in the South China Sea, as well as rights to the adjacent waters. Its claims overlap with those of Brunei, Malaysia, the Philippines and Vietnam.
In a formal 2016 statement that claimed sovereignty over the Pratas, Paracel, Spratly and Zhongsha islands, Beijing said this also covered territorial seas, exclusive economic zones and the continental shelf, as well as historic rights across the waterway.
Chen from the National Chengchi University warned that rising sea levels could see countries losing territory, which raised fundamental questions over statehood as well as maritime boundaries.
She added that a report from the International Law Commission last year said these aspects and the question of climate refugees were all “inextricably linked”.
As a result, “the legal response tends towards either offering contemporary interpretations of existing international instruments and rules, or formulating dedicated legal frameworks and mechanisms tailored to climate-related sea-level rise”, she said.
An emerging consensus
Faced with an existential risk, Pacific island states have already demanded that their statehood, established baselines and maritime zones should remain perpetual regardless of physical changes.
“There are a variety of processes [for freezing baselines]. One is to modify the convention, but this will be diplomatically and politically challenging,” Rothwell said.
“The other is through the development and evolution of state practice and its wide-ranging acceptance by states throughout the international community. There is evidence that this is occurring.”
The international consensus has begun leaning in their favour, with the International Law Commission recommending that states should not be obliged to update the baselines deposited with the UN even if there are physical changes.
The UN is also planning a high-level meeting on rising sea levels on Thursday.


China’s role
Chen at Ocean University said Pacific nations must continue surveying and officially depositing and publishing their baselines and maritime boundaries under Unclos requirements, while broader and more consistent state practice would also help to consolidate the emerging legal approach.
She argued that China could support these efforts through practical, demand-driven cooperation.
“Beyond financial assistance, China can help island nations conduct maritime surveying, verify coordinates for UN deposit and support domestic ocean legislation and law capacity-building, while integrating coastal protection and climate monitoring with protection for affected populations,” Chen said.
She added that China needed to ensure developing countries had a full say in rule-making, while “systematically documenting and articulating its own practices” in sea-level monitoring, coastal protection and maritime surveying – so that they can be properly understood and taken into account in the international legal process.
“Active engagement in international lawmaking, supported by scientific evidence, clearly articulated state practice and concrete legal proposals, is necessary if China’s interests and perspectives are to be properly reflected in emerging rules.”
Beijing has already laid the groundwork for this role. Last year, it pledged to combat rising sea levels through infrastructure upgrades and disaster early-warning systems, as well as expanding cooperation in coastal restoration and sustainable fisheries.
Chen said supporting Pacific island states over the issue of maritime boundaries aligned with a wider interest shared by coastal states, including China: preventing climate-related physical change from automatically producing an additional loss in law.
“Maritime boundaries established by treaties or other international mechanisms must remain stable and final,” she said.
“The underlying principle is that physical harm caused by climate change should not automatically be converted into a loss of existing lawful maritime entitlements.”
Historic rights
Diplomatic hurdles nevertheless persist. China’s UN representatives have suggested that legal debates on rising sea levels should incorporate the concept of “historic rights” alongside baseline stability.
“Rules in customary international law concerning historic waters, historic title, and historic rights are equally important foundations for asserting a nation’s maritime entitlements,” Wang Chen, a Chinese representative at the UN, told a meeting to discuss the issue last October.


“The concept also provides legal support for impacted nations seeking to preserve maritime areas and rights.
“China notes that useful discussions on the issue of historic waters were held but not reflected in the final report [by the International Law Commission], over which China expresses its concern.”
Chen from National Chengchi University said: “When China raises the issue of historic rights when discussing sea-level rise, other nations quickly associate it with its historic claims in the South China Sea, which make them wary due to recent maritime frictions.”
Common interests
Nations threatened by climate change know that waiting for legal recognition alone may not be enough to preserve their existence. Some are already seeking immediate guarantees of their statehood.
In the first agreement of its kind, in 2024 Tuvalu and Australia signed the Falepili Union Treaty, which guarantees Tuvalu’s statehood and maritime rights even if submerged, and opened the door to permanent migration to Australia.
Meanwhile, Rothwell said major powers had shown rare convergence on interpreting maritime law to accommodate rising sea levels.
Chen from Ocean University said Beijing need not rule out issue-specific cooperation with other-interested countries, as they shared mutual interests in technical standards for baseline coordinates, navigational safety, hydrographic surveying and legal capacity-building.
“The key is adhering to transparent cooperation led by island states’ needs and priorities, without attaching political conditions. In this way, China is not pitching a competing framework against other powers but offering a public good that island states can put into use and that can be woven into global rules.”
“Pacific island states should be treated as co-designers of the relevant rules, not merely as aid recipients or as states expected to choose between major powers,” Chen added.
Meanwhile, climate-threatened nations know that legal recognition alone cannot preserve their heritage.
In 2022, Tuvalu launched the world’s first digital nation project, using 3D lidar (light detection and range) scanning to build a virtual replica of the country.


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Rising sea levels are not an existential threat to China, but their impact on international law could have a knock-on effect in other areas


Rising sea levels are not an existential threat to China, but their impact on international law could have a knock-on effect in other areas.


Why China is weighing into the debate on how to respond to shrinking coastlines

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}Rising sea levels are not an existential threat to China, but their impact on international law could have a knock-on effect in other areas

Rising sea levels are not an existential threat to China, but their impact on international law could have a knock-on effect in other areas