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Window for saving world’s coral reefs rapidly closing

Friday, 5 January 2018

Source: James Cook University

The world’s reefs are under siege from global warming, according to a novel study published today in the prestigious journal Science.

For the first time, an international team of researchers has measured the escalating rate of coral bleaching at locations throughout the tropics over the past four decades.

The study documents a dramatic shortening of the gap between pairs of bleaching events, threatening the future existence of these iconic ecosystems and the livelihoods of many millions of people, according to lead author Professor Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies (Coral CoE).

"The time between bleaching events at each location has diminished five-fold in the past 3-4 decades, from once every 25-30 years in the early 1980s to an average of just once every six years since 2010," Professor Hughes said.

"Before the 1980s, mass bleaching of corals was unheard of, even during strong El Niño conditions, but now repeated bouts of regional-scale bleaching and mass mortality of corals has become the new normal around the world as temperatures continue to rise."

The study establishes a transition from a period before the 1980s when bleaching only occurred locally, to an intermediate stage in the 1980s and 1990s when mass bleaching was first recorded during warmer than average El Niño conditions, and finally to the current era when climate-driven bleaching is now occurring throughout ENSO (El Niño-Southern Oscillation) cycles.

Co-author of the study, Professor Andrew Baird of Coral CoE, said researchers had shown that tropical sea temperatures are warmer today during cooler-than-average La Niña conditions than they were 40 years ago during El Niño periods.

“Coral bleaching is a stress response caused by exposure of coral reefs to elevated ocean temperatures," Professor Baird explained

“When bleaching is severe and prolonged, many of the corals die. It takes at least a decade to replace even the fastest-growing species."

Another co-author, Dr C. Mark Eakin of the National Oceanic & Atmospheric Administration, said reefs had “entered a distinctive human-dominated era: the Anthropocene”.

"The climate has warmed rapidly in the past 50 years, first making El Niños dangerous for corals, and now we're seeing the emergence of bleaching in every hot summer," Dr Eakin said.

"For example, the Great Barrier Reef has now bleached four times since 1998, including for the first time during back-to-back events in 2016 and 2017, causing unprecedented damage," Professor Hughes explained. 

"Yet the Australian government continues to support fossil fuels.

"We hope our stark results will help spur on the stronger action needed to reduce greenhouse gases in Australia, the United States and elsewhere."

Their paper – “Spatial and temporal patterns of mass bleaching of corals in the Anthropocene” – is available here.

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Media Contacts:

Professor Andrew Baird
ARC Centre of Excellence for Coral Reef Studies
James Cook University
Townsville, Queensland, AUSTRALIA
P: +61 (0) 400 289 770 (currently in Sydney, AEDT/UTC +11)
E: Andrew.Baird@jcu.edu.au

Associate Professor Julia Baum
Department of Biology
University of Victoria
Victoria, British Columbia, CANADA
P: 1-250-858-9349 (PST/UTC -8)
E: baum@uvic.ca

Associate Professor Michael Berumen
Red Sea Research Center
King Abdullah University of Science and Technology
Thuwal, SAUDI ARABIA
P: +966 544 700 019 (available from 3-4 Jan, MSK/UTC + 3; 5-7 Jan, CET/UTC + 1)
E: michael.berumen@kaust.edu.sa

C. Mark Eakin, Ph.D.
National Oceanic & Atmospheric Administration
Silver Spring, Maryland, UNITED STATES
P: 1-301-502-8608 (EST/UTC -5)
E: mark.eakin@noaa.gov

Professor Nicholas Graham
Lancaster Environment Centre
Lancaster University
Lancaster, UNITED KINGDOM
P: +44 (0)7479 438 914 (available from 4 Jan, GMT/UTC)
E: nick.graham@lancaster.ac.uk

Professor Terry Hughes
Director, ARC Centre of Excellence for Coral Reef Studies
James Cook University
Townsville, Queensland, AUSTRALIA
P: +61 (0) 400 720 164 (NZDT/UTC +13)
E: Terry.Hughes@jcu.edu.au

Catherine Naum
Communications Manager
ARC Centre of Excellence for Coral Reef Studies
James Cook University
Townsville, Queensland, AUSTRALIA
P: +61 (0)7 4781 6067
M: +61 (0) 428 785 895 (AEST/UTC +10)
E: Catherine.Naum1@jcu.edu.au