"Places that had healthy coral reefs and intact mangroves were far less badly hit than places where the reefs had been damaged and the mangroves ripped out and replaced by beachfront hotels and prawn farms," said Simon Cripps, director of the Global Marine Programme at the environment group WWF Internationational.

"Coral reefs act as a natural breakwater and mangroves are a natural shock absorber, and this applies to floods and cyclones as well as tsunamis," he said in an interview from Geneva.

He compared the outcome of the December 26 tsunami in the Maldives, the low-lying archipelago which emphasises good coral management in its policy of upmarket tourism; and the Thai resort of Phuket, where mangroves and a coastline belt have been replaced by aquaculture and a hotel strip.

Both places were swamped and suffered severe economic damage. In the Maldives, just over 100 people have been counted as dead and missing in a populace of 270,000; in Phuket, where there is a roughly similar size of population at peak season, the toll is nearly 1,000.

Thailand's isolated neighbour, Myanmar, where much of the mangrove remains intact, was notably spared the scale of devastation which struck the Thai coast, WWF's deputy director for the Asia-Pacific, Dermot O'Gorman, told AFP, according to US satellite images and eyewitness accounts.

In India's southern state of Tamil Nadu, "areas in Pichavaram and Muthupet with dense mangroves suffered fewer human casualties and less damage to property compared to areas without mangroves," the British-based science website SciDev.Net says.

Doug Masson, a senior researcher at Southampton University's Oceanography Centre in southern England, said that even the best-managed coastal buffer offers no guarantee of a shield against a major tsunami, but it certainly helps to save lives.

"There is a big dampening effect if you have a coral reef. My feeling is that coral is what probably saved the majority of people in the Maldives. The reef broke up the tsunami and it travelled forward as a broken wave and so was far less deadly," he said.

"As for mangroves, the effect would be different. It would act as a dampener but the wave would not be broken up before it hits."

Mangroves are a complex ecosystem of tangled trees, growing in muddy, brackish coastal creeks.

In many parts of South and Southeast Asia, the mangroves have been chopped down to make way for tourism or growing seafood. Thailand, in becoming the world's biggest prawn exporter, lost almost half of its mangrove acreage between 1975 and 1993, according to Cripps.

Many of the tourist developments are set right on the beach, rather than located back from the sea, which means that vacationers and resort workers were doubly exposed to the tsunami after the loss of this natural buffer, said Cripps.

Jeff McNeely, chief scientist with the Swiss-based World Conservation Union (IUCN), said last week that reckless development in Indonesia and Thailand, in a geologically active region, had been the main driver for the high toll.

"(...) People have started to occupy part of the landscape that they shouldn't have occupied," he said.

"(...) The mangroves were all along the coasts where there are shallow waters. They offered protection against things like tsunamis. Over the last 20-30 years, they were cleared by people who didn't have the long-term knowledge of why these mangroves should have been saved."

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