Jim Loney, PlanetArk 14 Dec 07;
MIAMI - In less than 50 years, oceans may be too acidic for coral reefs to grow because of carbon emissions from the burning of fossil fuels by humans, according to research released on Thursday.
And unless still rising carbon dioxide emissions fall in the near future, existing reefs could all be dying by 2100, scientists said.
Australia's Great Barrier Reef, the world's largest coral expanse, and Caribbean reefs will be among the first casualties, according to the scientists who worked on a major coral project worldwide.
The study, to be published in Friday's issue of the journal Science, should serve as a warning to delegates to a UN climate conference in Bali, Indonesia, this week, the researchers said.
"We need rapid reductions in carbon dioxide levels," said Ove Hoegh-Guldberg, a marine science professor at Australia's University of Queensland and a lead author of the study.
"The impact of climate change on coral reefs is much closer than we appreciated," he said in a telephone interview from Australia. "It's just around the corner."
The study found emissions of carbon dioxide, the main "greenhouse" gas contributing to global warming, are boosting acidity so much that sea water covering 98 percent of all coral reefs may be too acidic by 2050 for some corals to live, and while others may survive they would be unable to build reefs.
"Unless we take action soon there is a real possibility that coral reefs, and everything that depends on them, will not survive this century," researcher Ken Caldeira said.
Coral reefs, delicate undersea structures resembling rocky gardens that are made by tiny animals called coral polyps, are important nurseries and shelters for fish and other sea life.
They are also considered valuable protection for coastlines from high seas.
Reefs are a critical source of food for millions of people and are important for tourism from Australia to the islands of the Caribbean and the Florida Keys.
MEDICAL TREASURE
They produce US$375 billion a year in economic value worldwide, according to The Nature Conservancy environmental group, and are considered a storehouse of potential 21st century medicines for cancer and other diseases.
The polyps secrete calcium carbonate to build the stony base of the reef. Corals grow slowly, as little as half an inch (one cm) per year and the fragile structures they create are easily damaged by ship groundings, storms and other threats.
The researchers, who based their work on computer simulations of ocean chemistry, said about one-third of carbon dioxide, or CO2, put into the atmosphere is absorbed by the ocean, slowing global warming but polluting the sea.
The CO2 produces carbonic acid, the substance that gives soft drinks their fizz. The acid reduces concentrations of carbonate-ions, which are critical to reef building.
Current levels of CO2 in the atmosphere are 380 parts per million, researchers said, but rising quickly as humans increase their emissions by burning fossil fuels.
If trends hold, the concentration could rise to 880 ppm by 2100. But even if atmospheric CO2 stabilized at 550 ppm, which would take a concerted international effort, no existing coral reef could survive, the researchers said.
"We have the world at stake here. It's a global emergency," said Hoegh-Guldberg. "We've got to have (CO2) levels falling by 2015."
Australian and Caribbean reefs are at the greatest risk because they already have lower carbonate-ion concentrations and therefore would "reach critical levels sooner," he said.
The research should serve as a warning to those who look after reefs to ramp up the fight against other threats to them, which include overfishing, pollution from nearby land and a host of diseases, the researchers said.
"We need to think of this as the straw that broke the camel's back," said Peter Sale of the United Nations University. (Editing by Michael Christie and Richard Meares)
Increasing Acid Could Kill Most Coral by 2050
Andrea Thompson, LiveScience.com Yahoo News 14 Dec 07;
SAN FRANCISCO — The world’s coral reefs face almost certain death as increasing amounts of carbon dioxide in the atmosphere are absorbed by the oceans, acidifying the water in which corals live, a new study warns.
In the past few decades, corals have come under increasing pressure from warming ocean waters, overfishing and disease. A recent study found corals in Pacific ocean were disappearing faster than previously thought.
The new study, to be presented tomorrow at a meeting here of the American Geophysical Union, points to yet another factor plaguing these underwater bastions of biodiversity: carbon dioxide.
As carbon dioxide is emitted through the burning of fossil fuels, some of it is absorbed by the world’s oceans.
“About a third of the carbon dioxide put into the atmosphere is absorbed by the oceans,” said study team member Ken Caldeira of the Carnegie Institution of Washington, “which helps slow greenhouse warming, but is a major pollutant of the oceans.”
When the carbon dioxide is absorbed in the water, it produces carbonic acid, the same acid that gives soft drinks their fizz. This acid also makes certain minerals dissolve more readily in seawater, particularly aragonite, the mineral used by corals and many other marine organisms to grow their skeletons.
Caldeira and his colleagues ran computer simulations of ocean chemistry based on a range of atmospheric carbon dioxide levels, from 280 parts per million (ppm) (pre-industrial levels) to 5,000 parts per million. (Present levels are 380 ppm and rising.)
Their findings, detailed in the Dec. 14 issue of the journal Science, show that if current emission trends continue, 98 percent of present-day reef habitats will be too acidic by mid-century for reef growth.
“Before the industrial revolution, over 98 percent of warm water coral reefs were bathed with open ocean waters 3.5 times supersaturated with aragonite, meaning that corals could easily extract it to build reefs,” said study co-author Long Cao, also of the Carnegie Institution. “But if atmospheric CO2 stabilizes at 550 ppm—and even that would take concerted international efforts to achieve—no existing coral reef will remain in such an environment.”
At greatest risk of these changes are Australia’s iconic Great Barrier Reef, the world's largest living structure, and the reefs of the Caribbean Sea.
To slow ocean acidification, Caldeira and Cao warn, will likely take more stringent and immediate reductions in carbon dioxide than would be needed to reduce the other effects of global warming.
“The science speaks for itself. We have created conditions on Earth unlike anything most species alive today have experienced in their evolutionary history,” said co-author Bob Steneck of the University of Maine. “Corals are feeling the effects of our actions, and it is now or never if we want to safeguard these marine creatures and the livelihoods that depend on them.”
Coral reefs threatened by rising CO2 levels: study
Yahoo News 13 Dec 07;
The survival of the world's coral reefs will be seriously threatened by 2050 if atmospheric levels of carbon dioxide (CO2) and the acidity of ocean waters continue to rise at the present rate, said a study published Thursday.
High acidity dissolves minerals in the water that speed up calcification of corals leading to their premature death, warned researchers of the Washington-based Carnegie Institution in their study in Science magazine.
Unless emissions of CO2 -- global warming's main contributor -- are stabilized and reduced, 98 percent of coral reef habitats will be immersed in excessively acid waters, said oceanographers and study co-authors Ken Caldeira and Long Cao.
Their estimates are based on computer models of the ocean water's changing chemical composition with rising CO2 levels in the atmosphere -- from pre-industrial 280 parts per million (ppm) to the current 380 ppm, all the way up to 500 ppm.
Carbon dioxide emissions are on the rise chiefly due to human activities, above all from the massive burning of fossil fuels, scientists said.
"About a third of the carbon dioxide put into the atmosphere is absorbed by the oceans, which helps slow greenhouse warming, but is a major pollutant of the oceans," said Caldeira.
The absorbed CO2 produces carbonic acid that dissolve certain minerals, especially argonite, which is used by corals to grow their skeletons, he said.
If atmospheric CO2 stabilizes at 550 ppm, said Cao, "no existing coral reef will remain in such an environment."
According to Bob Steneck of the University of Maine and another co-author of the paper, around one billion people in Asia depend on coral reef fisheries.
"Corals are feeling the effects of our actions and it is now or never if we want to safeguard these marine creatures and the livelihoods that depend on them," he added.
The authors will also present their study Thursday before the American Geophysical Union, in San Francisco, California.
