Corals Shrinking Around Equator Thanks To Global Warming
December 11, 2012

Global Warming Responsible For Coral Shrinking Around Equator

Brett Smith for - Your Universe Online

As the clamoring for a more comprehensive strategy to battle climate change continues, scientists are producing more and more research that suggests incremental changes in global temperature can have a massive effect on ecosystems.

A new study from a team of Australian and German researchers showed that when sea surface temperatures increased by about 0.7 degrees Celsius during the last interglacial warm period, the Earth´s equatorial regions saw a sharp decline in coral diversity.

“When the climate warmed rapidly during the Last Interglacial, coral species diversity was much lower close to the Equator than at higher latitudes,” said co-author John Pandolfi, a biologist from the University of Queensland.

“It appears that during this period the number of coral species present in equatorial oceans was only 50-60% of the diversity found further away from the equator, and diversity was greatest in the northern hemisphere.”

Based on the coral fossil record from the last major global climate change about 125,000 years ago, the researchers found that equatorial waters warmed to the point that they killed off many species of coral, up to 10 degrees of latitude on both sides of the equator.

This latest study, which appeared in journal Proceedings of the National Academy of Science of the United States (PNAS), builds on previous research that suggested coral reefs expanded their range from the equator during this same time period.

“Our results suggest that the poleward range expansions of reef corals occurring with intensified global warming today may soon be followed by equatorial range retractions,” the report states.

The study´s findings are particularly relevant today because the planet has already warmed by 0.7 degree Celsius over the past few hundred years, and modern equatorial diversity has been found to be noticeably lower than adjacent latitudes north and south.

“[The study] has serious implications for the nations of the Coral Triangle, such as Indonesia and the Philippines, where tens of millions of people rely upon the oceans for their livelihoods and food,” Pandolfi said.

“The picture that is forming is one of corals moving back and forth, towards the poles during warm periods, and retracting towards the equator in cooler times, in search of the most favorable water conditions,” he added. “It is going to be important to factor this kind of dynamism into how we manage them in the hot times which we now know lie ahead.”

Pandolfi, who has been studying fossilized coral reef deposits around the world for years, noted that many of the samples he collects are found on dry land.

“Many of these reefs lie 4-6 meters above today´s high tide mark, and are a clear indicator of how much the oceans rose during the last interglacial,” he explained. “The thought that just 0.7 of a degree of sea surface warming back then caused a 4-6 meter ocean rise is distinctly disturbing — because that is how much the Earth has already heated in the current warming episode, and the predictions are for a further one degree or more by 2050.”

Pandolfi also wondered what the effects of human activity might be in combination with warming temperatures.

“Corals, we know, have responded quite readily to rising sea levels in the absence of human stressors. The question will be: can humans respond equally well?”