Coral reefs at breaking point
Thursday 1 October 2009
Coral reefs are facing a spiral of decline, as warming temperatures continue to drive mass coral bleaching while future acidification threatens recovery and future growth.
© ZSL - James Godwin
While climate change negotiations are progressing very slowly, with many nations still stuck on political differences, the latest scientific information highlights a desperate urgency. This week a new paper puts a powerful light on the knife-edge situation facing the world’s coral reefs.
The work by renowned coral reef and climate scientists substantiates the findings of a July meeting hosted by the Royal Society. The conclusions are shocking. “From the perspective of these magnificent ecosystems, climate change has already gone too far” said Dr Charlie Veron, the world’s foremost authority on corals.
Coral bleaching is an increasing threat to coral reefs with a single event in 1997/1998 devastating an estimated 16% of the world’s coral reefs in one go. These early events were followed by regrowth of new corals, but heat-induced coral bleaching is now happening sufficiently frequently that few reefs can fully recover before they are hit again.
“We believe that atmospheric CO2 concentrations of 350ppm represented a threshold for the world’s reefs” said Veron. “Beyond that, damaging heating becomes too frequent and the ecosystem starts to decline. Today we are at 387ppm, and reefs are beginning to fail.”
“It’s not just that the reefs are beginning to die” said Dr Mark Spalding, Senior Marine Scientist at The Nature Conservancy, “it’s what they take with them. These are the rainforests of the sea, but they are also critical to people.
"They may be the first and most sensitive ecosystems to succumb to climate change, but they will not be alone.”
“Reefs are highly sensitive ecosystems. For years, many have been weakened by human activities and this has left them highly vulnerable” said Alex Rogers from ZSL and the International Programme on the State of the Ocean.
“Now we are also faced with the threat of acidification caused by the oceans absorbing CO2, with evidence indicating that the growth of reefs is already slowing down because of changes in ocean chemistry.”
The publication makes it clear that corals will continue to decline as long as atmospheric CO2 concentrations remain above 350ppm, but also draws attention to local policies which may help.
Sound management of reefs, controlling fisheries, minimising pollution, and protecting adjacent watersheds can leave reefs more resilient and capable of recovering faster. It may buy a little time, and that may be critical, but if we don’t get back to safe CO2 levels then coral reefs are highly unlikely to survive in the long run.
The threatened status of the world’s reefs highlights the urgency for the global community to resolve its differences and agree on a strong framework to reduce global greenhouse gas emissions.
