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Coral clues to climate: Reefs vanished for 2,500 years

Richard B. Aronson

Ian Macintyre, left, of the Smithsonian Institution and Steven Vollmer of Northeastern University pull out a core sample for the coral study they were co-authors on.

Coral reefs along Panama's Pacific coast completely collapsed for 2,500 years due to natural climate cycles, researchers reported in a study Thursday, adding that there's a lesson in the data for man-made climate change: ease up on greenhouse gasses and reefs will restore themselves.

"We can prevent coral reefs from shutting down again or recover them if they do shut down by reducing concentrations of greenhouse gases in the atmosphere and the ocean," study co-author Richard Aronson, a biology professor at Florida Institute of Technology, told msnbc.com.

The researchers reconstructed 6,000 years of coral reef history by driving pipes into reefs to pull out core samples. 


"We were shocked to find that 2,500 years of reef growth were missing," Lauren Toth, the lead author and a doctoral student, said in a statement announcing the study in the journal Science

The team found the same gap in earlier studies by other researchers as far away as Australia and Japan, and tied the collapse to an intensification of the natural climate cycle that produces El Nino and La Nina weather events.

Aronson emphasized that the fact that coral reefs returned does not mean mankind can expect them to survive a climate made warmer by industrial emissions of carbon dioxide.

"It is quite the opposite," he said. "Environmental pressure caused the reef ecosystems to collapse, and relieving that pressure allowed recovery."

"The same message," he added, "applies to human-caused climate change: by changing the climate we are stressing corals and coral-reef ecosystems, and we will have to stop doing that if we are going to save the reefs."

John Bruno, a marine biology professor at the University of North Carolina at Chapel Hill, said the study is valuable for showing that the biggest threat facing coral reefs is climate change.

Lauren T. Toth

This coral on Panama's Pacific coast was bleached by a 2010 warming event triggered by El Nino.

"Our modern coral reefs are supremely sensitive to subtle changes in climate even in the absence of local impacts like fishing and pollution," he wrote in a commentary for msnbc.com.

"In other words, in contrast to what has been argued in a number of high profile essays, reefs do not have to be overfished and polluted to be harmed by climatic fluctuations," wrote Bruno, who was not involved in the study.

"Everyone agrees that overfishing, particularly the depletion of predators from coral reef ecosystems, is an enormous, global problem," he added. "But the current science indicates that this problem is largely unrelated to the climate change problem. We urgently need to tackle both problems -- simultaneously and with equal vigor and commitment. Unfortunately, solving one will not negate the other."

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