Stories From the Coral Triangle

Coral Triangle Reefs, even more at risk than we thought?

Keen to discover what fate befalls corals when temperatures climb dramatically, the researchers took a metaphorical trip back in time to look at the fossil coral record from the last major episode of global warming--some 125,000 years ago. Not unsurprisingly, they found evidence of a sharp decline in coral diversity near the equator.

"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," says Professor Pandolfi of the Australian Research Council Centre of Excellence for Coral Reef Studies and Director of the Centre for Marine Science at the School of Biological Sciences, at the University of Queensland.

This period corresponds to the interglacial warm period, which saw sea surface temperatures warm by about 0.7 degrees Celsius. Says Pandolfi, this was enough to lead to an exodus of many coral species out of equatorial waters up to 10 degrees of latitude on either side of the equator. These results suggest that in a first stage of warming, corals expanded their range as a result of global warming, followed by a retraction in the equator.

If one is to trust the fossil record then, corals are nomadic in the sense that they change location -- towards the poles during warm periods, and towards the equator during cooler periods, depending on where water conditions are the most favourable.

Professor Pandolfi is concerned by his findings. He shares, "the thought that just 0.7 of a degree of sea surface warming back then caused a 4-6 metre 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." 

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