Coral Reef Stress Map: Big Pic

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August 17, 2011 -- Worried about the future of your favorite coral reef? If the dot above is green, yellow, or orange then actions taken now to reduce local, human-induced stress -- such as urban and agricultural run-off, sewage and sediment loads, and overfishing -- will likely reduce the reef's vulnerability to bleaching events from rising ocean temperatures.

Currently reefs around the world are expected to encounter "temperatures of more than 2 degrees Celsius [3.6 degrees Fahrenheit] above normal thresholds by the turn of the century," reported marine researchers from the Wildlife Conservation Society and other groups in a recent report in the online journal PLoS One. That is in addition to the stress humans are already placing on these valuable resources.

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Managing the local human-induced stress problems however is sometimes seen as a thankless task given the overshadowing threat of rising ocean acidification and global average ocean temperatures due to atmospheric carbon pollution.

Which is why computational ecologist Joseph Maina of Macquarie University in Sydney, Australia and colleagues from New York, The Netherlands, and the United Kingdom, decided to identify the reefs with the best chance at success if human management of the reefs improved locally.

The reefs in red? Doomed.

It's that simple.

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The reefs in red are ones that, for example, don't have the needed physical oceanographic factors that could buoy them through the changing times ahead, such as neighboring cold water currents, enough wind to stir surface temperatures, or protection from ultra-violet radiation. These are reefs already depleted of biodiversity, and under such high stresses that the effort to better manage the reefs would be an extremely costly investment.

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“When radiation stress and high fishing are combined, the reefs have little chance of surviving climate change disturbances because they both work against the survival of corals that are the foundation of the coral reef ecosystem,” said co-author Tim McClanahan, WCS Senior Conservationist and head of the society’s coral reef research and conservation program.

What should reef lovers of these red-dotted regions do? Move.

"Under this framework, effective local management needs to target moving reef locations, especially those that are moderately exposed to climate related stress, towards low reinforcing conditions through improved water quality," the authors report.

That's not a new idea. Aquariums have been swapping coral and growing their own for years, but not for use in the ocean environment - due to the risk of invasive species contamination. Instead coral farms, where pieces of broken bits of coral from a local site are raised in protected beds to build new reefs nearby, are becoming a needed replacement strategy in several high tourist regions, such as off the coast of Florida.

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The only problem is these baby reef farms take years to grow only a few inches. But if management practices take moving reefs as a serious option for species survival then maybe there is time to relocate even the dots in red.

by Christina Reed

Image: Stress map of coral reefs around the world. Click on the map or here to see a larger version. (Courtesy of Tim McClanahan)