WASHINGTON (Reuters) - The world's wetlands, threatened by development, dehydration and climate change, could release a planet-warming "carbon bomb" if they are destroyed, ecological scientists said on Sunday.

Wetlands contain 771 billion tons of greenhouse gases, one-fifth of all the carbon on Earth and about the same amount of carbon as is now in the atmosphere, the scientists said before an international conference linking wetlands and global warming.

If all the wetlands on the planet released the carbon they hold, it would contribute powerfully to the climate-warming greenhouse effect, said Paulo Teixeira, coordinator of the Pantanal Regional Environment Program in Brazil.

"We could call it the carbon bomb," Teixeira said by telephone from Cuiaba, Brazil, site of the conference. "It's a very tricky situation."