FORT LAUDERDALE - Coral reefs need to be put on "life support" if they are to survive climate change, but their ultimate survival is dependant on major reductions in fossil fuel emissions, say experts.

"We're going to hear lots of bad news about corals in the next few decades," Rich Aronson, president of the International Society for Reef Studies, told 3,000 scientists, conservationists and policy makers at the 11th International Coral Reef Symposium (ICRS) in Fort Lauderdale, Florida Monday.

Climate change is making the ocean too warm and too acidic for most corals species to survive beyond the year 2050, many marine scientists now believe.

"The situation is serious to the point of desperation," Aronson told IPS in an interview.

Past and present carbon emissions from burning fossil fuels have already altered the oceans, leading to declines in corals in many areas. This trend will continue for decades even if it were possible to eliminate all emissions today, scientists say. Current emissions are running at eight to nine gigatonnes a year and rising, resulting in dramatically altered oceans where few of the current coral species will be able to survive.

"This is a pivotal moment. We must act strongly and immediately if we are to have coral reefs as we know them," Aronson said.

The action he and others urge involves major reductions in carbon emissions, protecting reefs from overfishing, pollution and other threats and helping corals be more resilient so they can better withstand changing conditions. The latter will act as a kind of life support system until the world community manages to sharply reduce carbon emissions. That may give corals the time they need to adapt to a changed ocean. Currently the rate of change is far too rapid for species to adapt, experts here say.

Coral reefs support about 25 to 33 percent of the oceans' living creatures. Some one billion people depend directly and indirectly on reefs for their livelihoods. Sea birds and many species of fish would affected by the loss of reefs.

Surprisingly, most scientists pegged overfishing as the biggest threat to corals just four years ago at the last International Coral Reef Symposium, Joan Kleypas of the National Centre for Atmospheric Research in Boulder, Colorado told the symposium. In the intervening four years, a great deal of research has been completed on the impacts of climate change on the oceans, and that has now convinced nearly all experts that it is by far the biggest threat to oceans.

Most corals begin to die when ocean temperatures increase by more than 2.0 degrees C and that is likely to happen under nearly all future carbon emission scenarios before 2100. Detailed computer models show that all corals will suffer severe bleaching in one to five years. If emissions decline rapidly in the next decade and if corals are more resilient to ocean warming, then there is hope, according to recent research.

There is some evidence that some corals can survive some warming of ocean temperatures, but there is no solution for acidification, says Klepas.

The oceans naturally absorb carbon from the atmosphere but because of human emissions they are absorbing more and more. This additional carbon has altered the oceans' chemistry, making them 25 to 30 percent more acidic. Each day, the oceans absorb 30 million tonnes of CO2, gradually and inevitably increasing their acidity, and leaving less calcium carbonate in the water for corals and shell-form species like phytoplankton to grow or maintain their skeletons.

"Acidification affects all marine species, not just corals," Kleypas noted. However, little research has been done to understand specifically what those effects may be.

Kleypas admits it looks impossible to save corals, but she remains hopeful. "We need to keep CO2 levels at a reasonable rate and corals may be okay," she said.

There is enough information about how to reduce carbon emissions and even a growing realisation that such reduction may not be costly in economic terms, Aronson said. Protecting reefs from other threats like overfishing and pollution is not difficult, but will require political leadership. Saving corals needs to be an international effort spearheaded by the United Nations.

"We (scientists) have to be pragmatic and we have to be smart about politics," Aronson said. "All of us -- scientists, conservationists and the public -- have to rise up and fight to protect reefs."

© 2008 Inter Press Service