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Immediate and drastic action needed to save coral reefs

New research has revealed that while we still have a chance to save coral reefs, time is quickly running out. The study from the ARC Centre of Excellence for Coral Reef Studies suggests that under an intermediate emissions scenario, the growth rate of some reefs may keep pace with sea level rise, but only for a short time.

According to Professor Morgan Pratchett, the results show that the growth of coral reefs will be stunted unless carbon dioxide emissions are drastically reduced.

“The threat posed by climate change to coral reefs is already very apparent based on recurrent episodes of mass coral bleaching,” explained Professor Pratchett. “But changing environmental conditions will have other far-reaching consequences.”

Professor Ryan Lowe said that modern coral reef structures reflect a balance between a wide range of organisms that build reefs, not just corals. This includes rock-hard coralline algae that bind reefs together.

“While the responses of individual reef organisms to climate change are increasingly clear, this study uniquely examines how the complex interactions between diverse communities of organisms responsible for maintaining present day coral reefs will likely change reef structures in the future,” said Professor Lowe.

The researchers calculated how the rates of coral reef growth will respond to ocean acidification and warming under three different carbon dioxide emissions scenarios: low, medium and worst-case.

“All reefs around the world will be eroding by the end of the century under the intermediate scenario,” said Dr. Scott Smithers. “This will obviously have serious implications for reefs, reef islands, as well as the people and other organisms depending upon coral reefs.”

Rising ocean temperatures can cause mass coral bleaching and reduce the ability of calcifying corals to form their calcium carbonate skeletons.

The investigation was focused on net calcification, bioerosion, and sediment dissolution rates measured across 183 distinct reefs in the Atlantic, Indian, and Pacific Oceans.

The results show that even under a low emissions scenario, reefs will suffer severely reduced growth rates. 

“While 63% of reefs are projected to continue to accrete by 2100 under the low-impact pathway, 94% will be eroding by 2050 under the worse-case scenario,” said Dr. Christopher Cornwall. “And no reef will continue to accrete at rates matching projected sea-level rise under the medium and high-impact scenarios by 2100.”

“Our study shows changing environmental conditions challenge the growth of reef-building corals and other calcifying organisms, which are important in maintaining the structure of reef systems,” said Professor Pratchett. “Saving coral reefs requires immediate and drastic reductions in global carbon emissions.”

The study is published in the journal Proceedings of the National Academy of Sciences.

By Chrissy Sexton, Staff Writer

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