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Against all the odds, a number of shape-shifting islands in the middle of the Pacific Ocean are standing up to the effects of climate change. For years, people have warned that the smallest nations on the planet - island states that barely rise out of the ocean - face being wiped off the map by rising sea levels. Now the first analysis of the data broadly suggests the opposite: most have remained stable over the last 60 years, while some have even grown.

Paul Kench at the University of Auckland in New Zealand and Arthur Webb at the South Pacific Applied Geoscience Commission in Fiji 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 that time, local sea levels have risen by 120 millimetres, or 2 millimetres per year on average. Despite this, Kench and Webb found that just four islands have diminished in size since the 1950s. The area of the remaining 23 has either stayed the same or grown,

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."