Urgent action needed to save the reef while we still can, scientists warn
THE IMPACTS OF LAST year’s coral bleaching event on the Great Barrier Reef surpassed not only all previous recorded bleaching events, but any single other disturbance suffered by the World Heritage-listed natural icon, including severe tropical cyclones.
The researchers conducted a detailed analysis of three major bleaching events suffered by the reef (in 1998, 2002 and 2016) using aerial and underwater surveys, combined with satellite-derived sea surface temperature data. They found that the distinctive geographical footprint of bleaching was primarily driven by patterns of sea temperatures.
Aerial view of a severely bleached reef along the inner shelf between Cape York and Cape Tribulation, Great Barrier Reef, March 2016. (Credit: James Kerry, ARC Centre of Excellence for Coral Reef Studies)
“In each of the three events since 1998, the pattern of bleaching matches exactly where the warmest water was each year,” explained Dr Janice Lough, a Senior Principal Research Scientist at the Australian Institute of Marine Science. In general, unbleached reefs were further south, where waters were mostly cooler.
Janice was one of 46 experts who co-authored the paper, which is published in the journal Nature today.
The researchers also found that protecting reefs from over-fishing and improving water quality made no difference to the impacts of the extreme heatwave of 2016 – although they pointed out that these measures would be important in the recovery of the bleached reefs in the long-term.
More bleaching in store for 2017
Based on the findings, it’s little wonder the damage caused by the reef in 2016 was so extensive, with sea surface temperatures last summer the highest on record for the Great Barrier Reef.
“It broke my heart to see so many corals dying on northern reefs on the Great Barrier Reef in 2016. The severity of the 2016 bleaching was off the chart,” said lead author Professor Terry Hughes, from the ARC Centre of Excellence for Coral Reef Studies at James Cook University (JCU) in Townsville, Queensland.
Professor Morgan Pratchett, another co-author on the paper, said the new findings “unequivocally show that the conservation of the Great Barrier Reef is intimately tied to both national and international climate policy, requiring an immediate reduction in emissions.”
Graveyard of Staghorn coral, Yonge reef, Northern Great Barrier Reef, October 2016. (Credit: Greg Torda ARC Centre of Excellence for Coral Reef Studies)
Scientists are now remobilising to conduct more surveys as another coral bleaching event already appears to be underway in 2017. “We’re hoping that the next two to three weeks will cool off quickly, and this year’s bleaching won’t be anything like last year,” said Terry, who added that the researchers had unfortunately also found that prior bleaching did not appear to ‘toughen up’ coral for future events.
“With rising temperatures due to global warming, it’s only a matter of time before we see more of these events. A fourth event after only one year is a major blow to the reef,” he said.
According to Morgan, who is also from JCU, the best-case scenario for the reef would be to contain future temperature increases through immediate emissions reductions. “We still have the opportunity to ‘save’ the Great Barrier Reef, but that window of opportunity is closing fast,” he said.
The worst case scenario, however, would be that we are now “firmly within an era where we are committed to major bleaching events such as last year’s occurring almost annually,” Morgan said. This, he added, would prevent the recovery of coral between bleaching events, leading to extensive loss of coral.
“We need to remember that without corals, the entire coral reef ecosystem is compromised, which will have devastating impacts on major industries and communities that are reliant on the reef,” Morgan said.
- 2500 experts plead for better management of the Great Barrier Reef
- In pictures: Close-up look at the Great Barrier Reef’s bleaching
- New world-first plan says only 10% of reefs to survive past 2050