I visited the island of Tuvalu in the Pacific Ocean three decades ago as the environmental assessor for an aid-funded engineering consultancy. Pollution of the freshwater lens and scavenging of protective shoreline coral rubble for construction were problems even then. As you note (see Nature 526, 624–627; 2015), these may drive exodus sooner than rising sea levels. Nobody likes to be forced out of their home. But small oceanic nations hold a valuable asset: sovereignty. Tuvalu already profits from its own Internet domain (.tv), and sovereign nations have United Nations votes, which are effectively on the market. They can operate attractive tax regimes. They can declare marine reserves and sell rights to fisheries, seabed mining or reef tourism. All of these make money, and it does not have to be divided between many people. They can all be done even if nobody lives there in person. Citizens of such small island nations could thus become well-off expatriates, as well as refugees.