Tuesday, 8 June 2010 8:25 AM

Climate Change - Good for Islands?

According to a report by New Scientist magazine, climate change may be having a positive effect on small islands in that it has helped some of them stay stable in size and some to grow.

The report, by Wendy Zuckerman, refers to the first analysis of the data of a study by Paul Kench at the University of Auckland in New Zealand and Arthur Webb at the South Pacific Applied Geoscience Commission in Fiji which 'used historical aerial photos and high-resolution satellite images to study changes in the land surface of 27 Pacific islands over the last 60 years' during which time 'local sea levels have risen by 120 millimetres, or 2 millimetres per year on average'.

According to the report, Kench and Webb found that just four islands have diminished in size since the 1950 and the area of the remaining 23 has either stayed the same or grown.

This excerpt is taken directly from the article, titled Shape-shifting islands defy sea-level rise:

Webb says the trend is explained by the islands' composition. Unlike the sandbars of the eastern US coast, low-lying Pacific islands are made of coral debris. This is eroded from the reefs that typically circle the islands and pushed up onto the islands by winds, waves and currents. Because the corals are alive, they provide a continuous supply of material. "Atolls are composed of once-living material," says Webb, "so you have a continual growth." Causeways and other structures linking islands can boost growth by trapping sediment that would otherwise get lost to the ocean.

All this means the islands respond to changing weather and climate. For instance, when hurricane Bebe hit Tuvalu in 1972 it deposited 140 hectares of sedimentary debris onto the eastern reef, increasing the area of the main island by 10 per cent.

Kench says that while the 27 islands in his study are just a small portion of the thousands of low-lying Pacific islands, it shows that they are naturally resilient to rising sea levels. "It has been thought that as the sea level goes up, islands will sit there and drown," he says. "But they won't. The sea level will go up and the island will start responding."

John Hunter, an oceanographer at the University of Tasmania in Australia, says the study is solid, and good news for those preparing evacuations. The shifting shape of the islands presents a challenge, however. Even on islands where the total land mass is stable or grows, one area may be eroded while another is being added to. It's not possible to simply move people living in highly urbanised areas to new land, says Naomi Biribo of the University of Wollongong in New South Wales, Australia.

Webb and Kench warn that while the islands are coping for now, any acceleration in the rate of sea-level rise could overtake the sediment build up. Calculating how fast sea levels will rise over the coming decades is uncertain science, and no one knows how fast the islands can grow.

Barry Brook, a climate scientist at the University of Adelaide in Australia and a supporter of the 350 campaign - which calls for the most stringent global emissions targets in the hope of saving low-lying states from sea-level rise - points out that sea-level rise is already accelerating. But, while he was initially surprised by the findings, he agrees with Webb and Kench's analysis. "It does suggest that islands have been able to adapt to sea-level rises," he says.

Letters to the Editor All Letters
By STEVE BANI Vura Heights, East Honiara
By GEOFFREY MAURIASI USP, Lacuala Campus, Fiji
By CHARLES KOULI Gizo, Western Province