"What we have seen in the tsunami crisis is that the areas that were protected naturally suffered less than those that were more exposed," Friends of the Earth Chairwoman Meena Raman said.

In many areas, mangrove forests and coral reefs that once acted as natural buffers have been replaced with hotels, shrimp farms, highways, housing and commercial developments.

But in India, Malaysia and Sri Lanka, coastal "green belts" mitigated damage from the Dec. 26 tidal wave, which killed more than 150,000 in one of the worst natural disasters on record, the group said.

"The full fury and wrath of the tidal waves were felt in areas where nature's green belts of coral reefs and mangroves no longer exist or were never present in the first place," the Amsterdam-based organisation said in a statement.