The world has lost nearly one-fifth of its coral reefs, and much of the rest could be destroyed by increasingly acidic seas if climate change continues unchecked, a conservation group warned Wednesday.
Rising temperatures from greenhouses gases are the latest and most serious threats to coral, which are already being damaged by destructive fishing methods and pollution, according to the International Union for Conservation of Nature (IUCN).
About 19 percent of coral reefs have disappeared during the last 20 years, said IUCN's director general, Julia Marton-Lefèvre.
"If current trends in carbon dioxide emission continue, many of the remaining reefs will be lost in the next 20 to 40 years," Marton-Lefèvre said at Wednesday's U.N. talks, which are focused on creating a new climate change treaty.
"Climate change must be limited to the absolute minimum if we want to save coral reefs. We need to move forward and substantially cut emissions," she said.
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Increasing carbon dioxide levels in the atmosphere, which fuels global warming, is raising ocean levels and temperatures, said Olof Linden of the World Maritime University in Malmö, Sweden.
When oceans absorb carbon dioxide from air, the gas reacts with water to produce carbonic acid.
That makes the water more acidic, dissolving the calcium shells of reef-building coral and other creatures that rely on the mineral.
(Related: "A Third of Reef-Building Corals at Risk of Extinction" [July 10, 2008].)
A report by the Global Coral Reef Monitoring Network, of which IUCN is a member, also said all the world's coral reefs could be considered threatened if current forecasts from the U.N.'s Intergovernmental Panel on Climate Change and coral reef experts are heeded.
Because such reefs are home to more than a quarter of all marine species, their loss could be devastating for biodiversity in the world's oceans, experts say.