If the world won't or can't act to slow global warming, it must at least help disappearing states prepare for life after land , writes law of the sea academic Professor Rosemary Rayfuse, in an opinion piece that first appeared in The New York Times.

Rising sea levels could threaten the existence of small island states such as Tuvalu, Kiribati, the Marshall Islands and the Maldives. If the international community cannot or will not slow global warming, the least it can do is help those states prepare for life after land by recognising a new category of state — the deterritorialised state.

If we do nothing and these nations become uninhabitable, their citizens will not only become displaced persons seeking refuge in other countries; they will also lose control of their vast maritime zones, including valuable fisheries and mineral deposits, which will likely become the property of neighboring states or the global commons.

A few solutions have already been offered. Disappearing states could try to acquire territory from another state. However, no other government is likely to give up some of its land, no matter the price. The construction of artificial islands has also been proposed, but the financial, engineering, cultural and legal challenges may be insurmountable.

The best scenario under current international law appears to be for disappearing states to enter into some form of federation with another state. However, a merger would threaten their cultural identities and likely oblige them to relinquish control over their resources.

Simply continuing to recognise deterritorialised states as full states is a better solution. A deterritorialised state would consist of a government entity that would continue to represent the rights of its citizens at the international level and vis-à-vis their new host state or states. It would manage the state's maritime zones and other assets for the benefit of its citizens wherever they might be located. This way, displaced populations would be able to finance their future in a new country, instead of depending on goodwill alone.

Traditionally, international law requires a state to have a permanent population, a defined territory, a government and the capacity to deal with other states. However international law is not static, and there is precedent for deterritorialised states. The Holy See was recognised as sovereign despite losing its territory, Vatican City, for a few decades following the unification of Italy in the 19th century. The Order of St John, or the Knights of Malta, was considered sovereign despite having lost its territory in 1798.

Functional, or nonterritorial, sovereignty has also been recognised for governments-in-exile and, to a certain extent, for populations like the Palestinians, the Inuit and the Maori that have been displaced or colonised, while nonstate entities like Taiwan and the European Union have exercised aspects of sovereignty, like the signing of treaties.

The United Nations should affirm that if an island nation loses its permanent population and territory to rising seawater, the world will continue to recognise its sovereignty as a nation.

A version of this op-ed first appeared in The New York Times.

Media contact: Steve Offner, UNSW Media | 02 9385 8107