This is what we know. As has happened during countless past climatic shifts, some areas of the Earth will flood, others will emerge from their shroud of ice, and previously non-navigable sea-lanes will open up.
The difference this time is that we are in an era of international law, in which our political boundaries are closely and rigidly tied to our physical ones. This is especially true when it comes to maritime borders that, legally, are often determined by coastlines. As sea level changes cause those coastlines to retreat, advance or, in the extreme case of low-lying islands, disappear completely, might maritime boundaries shift?
To understand what that might mean, it is worth looking at three scenarios, each highlighting a different (hypothetical but possible) legal situation.
Shifting borders between maritime neighbours
Usually, a state is entitled to an exclusive economic zone of 200 miles off its coast, unless its zone butts up against the zone of another country, in which case the two countries typically split the difference. For example, if two nations are separated by 100 kilometres of ocean, they might set their maritime border 50 kilometres from each shore. This is the case, for example, with the Cuba–US border. The problem is that the US coastline is measured from the Florida Keys, an extremely low-lying region, while Cuba is relatively mountainous and not as likely to lose ground to rising sea levels.
So, leaving the Bahamas aside, if the Keys flood and the Florida coastline retreats up towards the middle of the state, while Cuba stays more or less as it is, should the border be moved to reflect the new midpoint? That would put the entrance to the Gulf of Mexico in Cuban waters and, while southern Florida would be submerged, it would still be an impediment to shipping, meaning traffic would have to loop down through Cuban waters.
Dramatically eroded Exclusive Economic Zones (EEZ)
If rising sea levels cause a country’s coastline to retreat inland, should its EEZ retreat by the same amount? The UNEP, University of Dacca, World Bank and others have published a map that shows a 1.5-metre sea-level rise could potentially push Bangladesh’s effective coastline inland by hundreds of kilometres. If so, that could put many of the country’s much needed resources in to the territorial waters of neighbours India and Burma (Myanmar). Or even into international waters. Many coastal nations, including China, India, and the U.S., are in the same position.
Threats to sovereignty
Long before the low-lying small island states of the Pacific, Atlantic and Indian Ocean sink completely, inhabitants may have to be evacuated as salt water infiltrates groundwater, killing vegetation and leaving those without desalination plants also without fresh water. It is very likely that eventually at least one entire nation, for example Tuvalu, will have to be completely resettled. But can a nation exist without a physical state? If Tuvalu goes under the sea or is abandoned, will it lose its seat in the UN? Will its EEZ revert to international waters? Will it lose its lucrative .tv internet suffix?
Even this short list of three of the border troubles caused when our international legal system meets climate change shows there are very rough seas ahead.
Cleo Paskal is an Associate Fellow at Chatham House. The full report on borders and climate change can be found here.
This article first appeared in the Ecologist August 2007