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AVARUA, Rarotonga, Cook Islands (June 19, 2000 - Islands Business/PINA Nius Online)---Pacific Islanders can't rely on their coral reefs to shield them from ravages by the rising sea, according to University of the South Pacific scientist Dr. Paddy Nunn. The reefs as a savior? "They are not," he says in a paper delivered at the Rarotonga climate conference on his behalf.

Nunn has studied the sea level rise issue as it affects the Pacific Islands for nearly 20 years and is a leading authority on it. His stand on actual sea level rise is that long-term records from such locations as Honolulu indicate an average rise of 1.5 millimeters year for a century.

A United Nations report on climate change in 1995 estimated that by 2100 the average sea level would be between 15 centimeters cm and 95 centimeters higher than it was in 1990, and most likely 30 centimeters higher by 2050. That means the rate will accelerate by four times in the next 50 years.

He considers that in the 20th century "permanent inundation and erosion along most Pacific Islands shorelines can be attributed only to sea level rise."

For low-lying coasts, the rate at which they are eroded by a likely future acceleration of sea level rise depends on the nature of sandy sediment and the bedrock they lie on.

Coasts with bedrock foundations a little above sea level may endure for the next 10 to 30 years. As the sea level rises, erosion will fast accelerate as the tide reaches the surface level of bedrock.

That trend is a bad outlook for the coasts of Kiribati, the Marshall Islands, Tokelau and Tuvalu, he says. Coasts without exposed bedrock are already eroding badly and this will accelerate if the United Nations estimates are correct.

Brushing away coral reef protection theories as fallacies, Nunn says that in post-glacial sea rise times 13,000 to 6,000 years ago a few coral reefs grew upwards at the same rate the sea rose. But such reefs were not normal in the Pacific. Reefs that grew more behind the sea level rise rate were more common.

"Having been adapted to growing slowly at only a slowly-changing sea level for the last 6,000 years, most modern coral reefs in the Pacific Islands are dominated by species suitable for lateral, not vertical growth." It would take decades for these reefs to begin to grow upwards as fast as sea level rise.

Existing reefs are in too poor condition to react quickly to sea level rise, Nunn says. Many had been harmed by human activity, higher storm frequencies and starfish attacks. Bleaching is also attacking them, brought on by the warming of the ocean's surface water. "Stress from many sources will increase in the future, including increased population densities on many Pacific Islands coasts and the incidences of coral bleaching and associated reef deaths are likely to increase.

"This will reduce the ability of reefs to protect existing shorelines and remove their potential ability to do the same in the future as the sea level rises. Island coasts will therefore become more vulnerable."

The final Nunn prognosis: "By the end of the 21st century the Pacific Islands region may look quite different to the way it does today. The area of low-lying coast, be it on low or high islands, will be significantly reduced and the descendants of the present human inhabitants of such places will have had to have moved elsewhere."

Higher coasts won't be much changed, but influxes of refugees will be causing other problems for them. "Many coral reefs in our region will have become submerged by more than half-a-meter. Added to these likely changes is the increase in population density, which is almost certain to have occurred by the end of the 21st century through most Pacific Islands nations.

"Increased population pressure on both the land and sea will exacerbate the effects of sea level rise. The time for effect counter-action is now," Nunn says. "There is no doubt that the worst effects of many of our islands' environmental problems could be effectively reduced by long-sighted management. Our great grandchildren will not thank us for our procrastination."

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