The scientists mapped the geographical pattern of heat exposure from satellites, and measured coral survival along the 2,300-km length of the Great Barrier Reef following the extreme marine heatwave of 2016.
The amount of coral death they measured was closely linked to the amount of bleaching and level of heat exposure, with the northern third of the Great Barrier Reef being the most severely affected. The study found that 29 per cent of the 3,863 reefs comprising the world’s largest reef system lost two-thirds or more of their corals, transforming the ability of these reefs to sustain full ecological functioning.
“The coral die-off has caused radical changes in the mix of coral species on hundreds of individual reefs, where mature and diverse reef communities are being transformed into more degraded systems, with just a few tough species remaining,” said co-author Prof Andrew Baird of Coral CoE at James Cook University.
“But, that still leaves a billion or so corals alive, and on average, they are tougher than the ones that died. We need to focus urgently on protecting the glass that’s still half full, by helping these survivors to recover,” said Prof Hughes.
The scientists say these findings reinforce the need for assessing the risk of a wide-scale collapse of reef ecosystems, especially if global action on climate change fails to limit warming to 1.5‒2 °C above pre-industrial levels.
“The Great Barrier Reef is certainly threatened by climate change, but it is not doomed if we deal very quickly with greenhouse gas emissions. Our study shows that coral reefs are already shifting radically in response to unprecedented heatwaves,” said Prof Hughes.
The researchers warn that failure to curb climate change, causing global temperatures to rise far above 2 °C, will radically alter tropical reef ecosystems and undermine the benefits they provide to hundreds of millions of people, mostly in poor, rapidly-developing countries.”
Citation: Hughes, TP, Kerry, JT, Baird, AH,Connolly, SR, Dietzel, A, Eakin, CM, Heron, SF, Hoey, AS, Hoogenboom, MO, Liu, G, McWilliam, MJ, Pears, R., Pratchett, MS, Skirving, WJ, Stella, JS and Torda, G (2018). Global warming transforms coral reef assemblages. Naturedoi:10.1038/s41586-018-0041-2
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CONTACTS FOR INTERVIEWS
Prof Terry Hughes Director, ARC Centre of Excellence for Coral Reef Studies Phone: +61 (0) 400 720 164 (AEST/UTC +10) E-mail: email@example.com
Prof Sean Connolly ARC Centre of Excellence for Coral Reef Studies at James Cook University Phone: +61 (0)7 4781 4242 (AEST/UTC +10) Email: firstname.lastname@example.org
Prof Andrew Baird ARC Centre of Excellence for Coral Reef Studies at James Cook University Phone: +61 (0) 400 289 770 (AEST/UTC +10) Email: email@example.com
C. Mark Eakin, Ph. D. U.S. National Oceanic & Atmospheric Administration College Park, MD U.S.A. Phone: +1 (301) 502 8608 (EST/UTC -5) Email: firstname.lastname@example.org
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Catherine Naum Communications Manager ARC Centre of Excellence for Coral Reef Studies at James Cook University Phone: +61 (0)7 4781 6067, +61 (0) 428 785 895 (AEST/UTC +10) Email: email@example.com
A severely bleached acroporid colony amongst the minimally bleached Porites colonies. Credit: ARC Centre of Excellence for Coral Reef Studies/ Gergely Torda