By James Grubel
CANBERRA, Oct 1 (Reuters) - The future is looking grim for coral reefs, home to bright tropical fish and a lure for tourists worldwide but also an early warning system for climate shift, leading coral scientist Ove Hoegh-Guldberg says.
Warming seas and increased ocean acidity will devastate more than 90 percent of the world's corals over the coming century unless urgent action is taken, Hoegh-Guldberg told Reuters.
"You'll get tougher corals surviving, but most of them are not tough enough to survive the sorts of temperatures we're going to throw at them over the next 100 years," Hoegh-Guldberg said.
The dire outlook points to a severe impact on tourism and the destruction of habitat for tropical fish, which are crucial to food supplies for millions of people around the world.
Hoegh-Guldberg, professor of marine science at Australia's University of Queensland, has made a career studying tropical corals and Australia's Great Barrier Reef. But he is worried there may be little coral left for future generations.
He was one of the Australian scientists to provide advice to the United Nations Intergovernmental Panel on Climate Change, which found urgent action could keep temperature rises to within 2 degrees Celcius (3.6 F).
Speaking from Ningaloo Reef on Australia's remote west coast, Hoegh-Guldberg said coral was particularly vulnerable to climate change due to a delicate balance between the living coral and the tiny plants that live in the coral cells.
When the sea temperature rises, the tiny plants struggle to survive, and the coral is unable to build the colourful carbonate shells which grow into reefs. The coral then turns white, or bleaches, and eventually dies if the sea doesn't cool.
OCEAN LITMUS TEST
Coral covers about 400,000 square km of tropical ocean floor, but needs sustained sunlight, warmer waters and high levels of carbonate to flourish.
The biggest is Australia's Great Barrier Reef, a collection of 2,900 reefs along 2,100 km of Australia's north east coast in a marine park the size of Germany. It generates A$6 billion in tourism activity and supports 66,000 jobs.
Since 1979, tropical sea temperatures have risen 0.7 degrees Celsius, leading to several massive cases of bleaching of coral, "the litmus paper of the ocean", Hoegh-Guldberg said.
The worst event happened in 1998, when coral bleaching affected every reef and killed 16 percent of the world's coral, including some of the toughest corals which have lived up to 1,000 years and previously adapted to change.
"These corals died in large numbers. As the old age guys, they should be really tough. But they also got affected," Hoegh-Guldberg said.
Tourist drawcards such as the reefs off Cayman Islands in the Caribbean have lost about half of their hard corals in the past decade, while about 42 percent of Australia's Great Barrier Reef, has been hit by varying levels of bleaching.
Hoegh-Guldberg said about 40 percent of carbon dioxide in the atmosphere is absorbed by oceans, which has made the oceans slightly more acidic, collapsing carbonate concentrations which coral needs to grow. He said research suggested coral had been able to adapt and even migrate due to ocean changes over thousands of years, but a rise in temperature of 2 to 3 degree would be too much.
"Essentially, the climate change is faster than the coral population can respond," he said. "So what you'll see is the coral population dropping to about five percent of what it is today." (For summit blog: summitnotebook.reuters.com/)