An Auckland University researcher has offered new hope to the myriad small island nations in the Pacific which have loudly complained their low-lying atolls will drown as global warming boosts sea levels.
Geographer Associate Professor Paul Kench has measured 27 islands where local sea levels have risen 120mm -- an average of 2mm a year -- over the past 60 years, and found that just four had diminished in size.
Working with Arthur Webb at the Fiji-based South Pacific Applied Geoscience Commission, Prof Kench used historical aerial photographs and high-resolution satellite images to study changes in the land area of the islands.
They found that the remaining 23 had either stayed the same or grown bigger, according to the research published in a scientific journal, Global and Planetary Change.
"It has been thought that as the sea level goes up, islands will sit there and drown," Prof Kench told the New Scientist. "But they won't.
"The sea level will go up and the island will start responding."
One of the highest profile islands -- in a political sense -- was Tuvalu, where politicians and climate change campaigners have repeatedly predicted it will be drowned by rising seas, as its highest point is 4.5m above sea level. But the researchers found seven islands had spread by more than 3 percent on average since the 1950s.
One island, Funamanu, gained 0.44 hectares or nearly 30 percent of its previous area.
And the research showed similar trends in the Republic of Kiribati, where the three main urbanised islands also "grew" -- Betio by 30 percent (36ha), Bairiki by 16.3 percent (5.8ha) and Nanikai by 12.5 percent (0.8ha).
Dr Webb, an expert on coastal processes, told the New Scientist the trend was explained by the fact the islands mostly comprised coral debris eroded from encircling reefs and pushed up onto the islands by winds and waves.
The process was continuous, because the corals were alive, he said.
In effect the islands respond to changes in weather patterns and climate -- Cyclone Bebe deposited 140ha of sediment on the eastern reef of Tuvalu in 1972, increasing the main island's area by 10 percent.
But the two men warned that while the islands were coping for now, any acceleration in the rate of sea level rise could re-instate the earlier gloomy predictions.
No one knows how fast the islands can grow, and calculating sea level rise is an inexact science.
Climate experts have generally raised estimates for sea level rise -- the United Nations spoke in late 2009 of a maximum 2 metre rise by 2100, up from 18-59cm estimated in 2007.
