Climate Change Affected Coral Reefs In Ancient Times
July 6, 2012

Climate Change Affected Coral Reefs In Ancient Times

Brett Smith for - Your Universe Online

Climate change has historically affected the growth of coral reefs, with some reefs experiencing a long-term growth stoppage around 4,000 years ago, according to newly published research in the journal Science.

An international team of scientists, who used radiocarbon dating and other research techniques, said that the growth stoppage they identified in eastern Pacific reefs took 2,500 years to recover from.

"We were shocked to find that 2,500 years of reef growth were missing from the frameworks," said lead author Lauren Toth of the Florida Institute of Technology. "That gap represents the collapse of reef ecosystems for 40 percent of their total history."

Using 17-foot-long hollow pipes, researchers took out cross-sections of the reefs along Panama´s Pacific coast. Radiocarbon dating and mass spectrometry techniques then applied to the cross-sections to identify they said was a period of "hiatus" in their growth.

The team then cross-referenced the coral-reef collapse data to documented historical changes in the El Niño—Southern Oscillation (ENSO), a climate pattern that occurs across the tropical Pacific Ocean approximately every five years. They found that the timing of the shutdown in reef growth matched up to a period of wild swings in ENSO.

"Coral reefs are resilient ecosystems," said Toth. "For Pacific reefs to have collapsed for such a long time and over such a large geographic scale, they must have experienced a major climatic disturbance. That disturbance was an intensified ENSO regime."

The activity of El Niño began some 4,200 years ago and climaxed about 3,000 years ago. Wildly fluctuating water temperature would have damaged the coral reefs and made it difficult for their populations to recover, according to the study. In addition, El Niño brought higher sea temperatures across the eastern equatorial Pacific and would likely have started the collapse of the Panama corals due to bleaching-related die-off.

About 3,800 to 3,200 years ago, the reefs were struck by another natural phenomenon. The study said a series of La Niña events, involving periods of unusually cold ocean temperatures, also negatively affected the health of these coral reefs.

Many are warning that the past may be a prologue with respect to not only eastern Pacific coral reefs, but reefs around the world. Climate change caused by greenhouse gas emissions may once again push the reefs “toward another regional collapse,” the study said.

Researchers explained that their study is yet another warning that human-induced climate change could have effects that reach far into the future.

"Climate change could again destroy coral-reef ecosystems, but this time the root cause would be the human assault on the environment and the collapse could be longer-lasting," said co-author Richard Aronson of FIT.

"Local issues like pollution and overfishing are major destructive forces and they need to be stopped, but they are trumped by climate change, which right now is the greatest threat to coral reefs."

On a more positive note, the team said that reefs have proven resilient in the past, so the possibility for recovery should be good if climate change can be stopped or reversed.