A creeping rise in sea levels tied to global warming, pollution and damage to coral reefs may make coastlines even more vulnerable to disasters like tsunamis or storms in future, experts said Monday.

Few coastal ecosystems are robust enough to withstand freak waves like the ones that slammed into Asian nations from Sri Lanka to Thailand Sunday, killing more than 22,000 people, after a subsea earthquake off Indonesia.

But global warming, poorly planned coastal development and other threats over which humans have some control are weakening natural defenses ranging from mangrove swamps to coral reefs that help keep the oceans at bay.

"Coasts are under threat in many countries," said Brad Smith at environmental group Greenpeace. "Development of roads, shrimp farms, ribbon development along coasts and tourism are eroding natural defenses in Asia."

Scientists say a build-up of heat-trapping gases in the atmosphere from human burning of fossil fuels threatens to trigger more powerful storms and raise sea levels, exposing coasts to more erosion.

Leaders of small island states will meet in Mauritius on Jan. 10-14 to debate threats such as global warming.

World sea levels rose on average by 10-20 cm (4 to 8 inches) during the 20th century and an additional rise of 9-88 cm is expected by the year 2100, according to latest report by the U.N. Intergovernmental Panel on Climate Change in 2001.

RISING SEAS

Island nations like the Maldives, swamped by the tsunami, could literally disappear beneath the waves if seas rise. And in Bangladesh, 17 million people live less than one meter above sea level, as do many in Florida in the United States.

Richard Klein, a senior Researcher at the Potsdam Institute for Climate Impact Research in Germany, said vulnerability to natural disasters often went hand in hand with poverty.

"Vulnerability has as much a social dimension as an environmental one," he said. The Netherlands could afford to build higher dykes to defend against the seas, for instance, but developing states could not.

He suggested better early warning systems for everything from cyclones to tsunamis in the Third World.

"And one of the first risks for small islands is not that they will be submerged (by rising sea levels) but there will be no fresh water," he said. Salt water would poison reservoirs of rainwater and purification equipment would be too costly.

Smith at Greenpeace said damage to coral reefs was also making coasts more vulnerable to battering by the sea.

An international report early this month showed that about 70 percent of the world's coral reefs had been ruined or were under threat from human activities, ranging from over-fishing to coastal pollution and global warming.

"Corals form a storm barrier and if they die many islands will be more vulnerable to cyclones," he said.