Sir David Attenborough joined scientists at the Royal Society in London today to warn that saving coral reefs from mass bleaching in a warmer ocean would take more than just limiting carbon dioxide emissions. We’ll have to start actively removing the gas from the atmosphere – perhaps through geoengineering, said the scientists. As the reefs go, so goes the ocean, warned Attenborough, who said that reefs act as "a barometer of the malaise that is afflicting the ocean at large.”
The one-day meeting, put on by the Royal Society, the London Zoo and the International Programme on the State of the Ocean (IPSO), brought together about two dozen coral reef and climate experts to draft a statement on the reefs’ sensitivity. The group’s statement concludes that stabilizing atmospheric carbon dioxide concentrations at 450 parts per million would still allow for climate change and ocean acidification leading to catastrophic losses. “To ensure the long-term viability of coral reefs,” they say, the level has to be brought down from today’s 387 parts per million to “significantly below 350 ppm”. Geoengineering is one option that could be considered for soaking up existing carbon, said Alex David Rogers of IPSO at a press briefing on the new document.
The 350 ppm figure is based on “simple correlation”, said J.E.N. “Charlie” Veron, the former chief scientist at the Australian Institute of Marine Science. The early 1980s brought the first isolated bleaching events, which the group argues were caused by ocean warming in response to earlier rises in carbon dioxide. These events were triggered when 320 ppm was passed, according to the statement; levels were up to 345 ppm by the 1980s, and at today’s 387 ppm reefs are in serious decline due to repeated mass bleaching. As carbon dioxide continues to climb, ocean acidification will take an additional toll on these ecosystems.
These observations are nothing new, but “people have been quite wary about actually stepping forward and making a firm statement about when some of these changes are going to occur,” said Rogers. What’s pushed this group to make the leap is alarm about the current state of reefs – and of climate policy. This is the latest – and most strident – of multiple manifestos from marine scientists urging policymakers to make ocean health a priority in the climate scenarios they’re aiming at. Reefs may be frustratingly sensitive to change, but we can’t afford to write them off: they’re not only storehouses of biodiversity but home to fish stocks on which 0.5 to 1 billion people depend for their livelihoods, said Rogers.