Tokelau, a group of islands administered by New Zealand - just 12sq km of land in more than 250,000sq km of Pacific Ocean - is expected, literally, to be wiped off the map by pollution. So are six other scattered strings of atolls, including similar dependencies and independent nations, among them the 1,196-island state of the Maldives in the Indian Ocean.
As carbon dioxide emitted by fuel burned in the world's cars, homes and industries, heats up the climate, many scientists believe that the seas will rise and eventually drown such low-lying islands.
Frustrated by their apparent powerlessness in face of such threats, the independent small island nations of the world are banding together. Last week representatives of nearly 40 of them met in New York to prepare for a world conference on their plight in Barbados next month. It will be the most important environmental assembly since the 1992 Rio Summit, and the first test of whether the world's leaders intend to implement the decisions they agreed there.
At first sight, most Small Island Developing States (SIDS), which range from St Lucia to Samoa, are relatively fortunate, and not just for their natural beauty and warm climates.
On average they are four times wealthier than Third World countries in general and 16 times better off than the poorest ones. They have relatively high life expectancies and low infant mortality. A high proportion are democracies, and they take up nine of the top 15 places held by developing countries in the UN's official Human Development Index, which measures quality of life.
They also receive an average of pounds 100 a year in overseas aid for each of their people - seven times the average for developing countries.
Though small may be beautiful, however, it is also vulnerable. Many of the world's gravest environmental problems are at their most acute in SIDS. They have so few resources - natural, human or physical - that environmental crises can quickly turn into economic disasters.
Three-quarters of all known animal extinctions in recent history have taken place among the rich wildlife of small islands. They tend to be densely populated. Proportionately, they are losing far more tropical forest each year than Brazil. Their small endowments of topsoil are rapidly being eroded. Their water supplies are usually limited and are increasingly being depleted by the tourism on which at least half their economies depend.
Tourism increases pollution - only one-tenth of the sewage produced by the 20 million people who visit the Caribbean each year receives any kind of treatment.
Increasingly dirty seas and oil spills imperil economies. And small islands are increasingly being used by bigger nations as dumping grounds for toxic wastes.
But the greatest threat of all comes from global warming. The highest point on the main island of Kiribas, in the Pacific Ocean, is 2ft above sea level; the scientists' best estimate is that the seas will rise higher than this over the next century.
But nations will become uninhabitable long before they physically sink beneath the waves, because the higher the seas rise, the more frequently storms will sweep water across them. And even small increases in sea level will cut away land and contaminate the underground fresh water supplies on which islanders depend.
Tuvalu, in the Pacific, is already submerged twice a year, and new building regulations stipulate that houses must be built on stilts.
A report by the government of the Marshall Islands has warned that many of their 50,000 people may have to be evacuated over the next few decades. The foreign minister has said that rising seas 'could annihilate the country as effectively as a nuclear bomb'.
Even relatively hilly countries are in danger, since most of their people and industries are concentrated on coastal strips. As the climate heats up, storms and hurricanes are expected to increase. A single one can cost a small island one-third or more of its annual GDP.
By last year, after an unprecedented series of hurricanes, 24 insurance companies had withdrawn completely from the Caribbean. Western Samoa's only fire and general insurer announced - after two record cyclones in less than 18 months - that it would cease all cover once existing insurance policies ran out.
All this has caused the SIDS to begin to flex some unexpected muscle. Thirty-six of them have combined to form the Alliance of Small Island States, and so control a large bloc of votes at the UN.
They were able to toughen up the treaty combating global warming, which was signed at the Earth Summit. And powerful countries have begun to court their support in their campaigns for election to the UN Security Council.
Next month's conference has come about at the Alliance's insistence, and should, for the first time, focus world attention on the SIDS and their vulnerability. Nitan Desai, the UN undersecretary-general responsible for the conference, says it will be a test case for the commitments made at the Earth Summit.
Helping the SIDS towards environmentally friendly development would be relatively cheap, precisely because they are so small. 'If we cannot handle the problems of small islands, where are we going to succeed?' he asks.