Global warming already affecting fragile coral reef eco-system, say experts

 

RISING SEA temperatures and the acidification of oceans due to global warming will “demonstrably change” coral reefs, one of the world’s most fragile eco-systems, according to a panel of experts.

“The impact of a warming climate on reefs is not a future event – complex changes have already begun that could fundamentally change what reefs look like in the future,” the International Coral Reef Symposium heard yesterday in Cairns, Australia.

The symposium, held every four years, is described as a “hotbed of the latest advances in coral reef science” and the research presented in Cairns is “fundamental in informing international and national policies and the sustainable use of coral reefs globally”.

“Tropical coral reef waters are already significantly warmer than they were and the rate of warming is accelerating,” said Dr Janice Lough, of the Australian Institute of Marine Science. “We are facing, for the foreseeable future, changes in their physical environment.”

A temperature rise of 0.5 degrees Celsius in tropical oceans over the past century has resulted in widespread coral bleaching and outbreaks of coral diseases. Current projections indicate that the tropical oceans could be 1 to 3 degrees warmer by the end of this century.

Mexican marine biologist Roberto Iglesias-Prieto warned that the changes would ultimately have a severe impact on millions of people who depend on coral reefs for food, storm protection and the income generated by tourism.

Prof Philip L Munday, of James Cook University in Queensland, said the direct effects of global warming, which are already occurring, include reduced coral cover and less habitat structure for fish. “That will mean fewer species and lower fish abundance,” he warned.

Even with the modest level of warming to date – compared to future projections – coral growth rates have slowed in recent decades on Australia’s Great Barrier Reef while increasing growth rates have been recorded on cooler reef sites off Western Australia.

“The latter is unlikely to be sustainable, given the setbacks in growth following coral bleaching and, as temperatures continue to warm, optimum temperatures for coral growth are exceeded,” Dr Lough said at a briefing on the impact of climate change.

Prof John M Pandolfi, of the University of Queensland, said some coral reef species may survive, but others could become extinct. Reefs already degraded from over-fishing or pollution “will be much less likely to handle the increase in temperature and ocean acidity”.

New research is also showing that the impact on corals will be “more variable than first realised”, he said, adding that management approaches “must become more sophisticated”, with a particular focus on reducing threats such as over-exploitation and pollution.

“There will be winners and losers in climate change and ocean acidification, but reefs will demonstrably change and, for most people’s idea of what reefs are, not for the better,” Prof Pandolfi said.

A full video of the briefing and is available online at icrs2012mediaportal.com