The unique study measured how many adult corals survived along the length of the world’s largest reef system following extreme heat stress, and how many new corals they produced to replenish the Great Barrier Reef in 2018. The loss of adults resulted in a crash in coral replenishment compared to levels measured in previous years before mass coral bleaching.
“The number of coral larvae that are produced each year, and where they travel to before settling on a reef, are vital components of the resilience of the Great Barrier Reef. Our study shows that reef resilience is now severely compromised by global warming,” said co-author Professor Andrew Baird.
“The biggest decline in replenishment, a 93% drop compared to previous years, occurred in the dominant branching and table coral, Acropora. As adults these corals provide most of the three-dimensional coral habitat that support thousands of other species,” he said.
“The mix of baby coral species has shifted, and that in turn will affect the future mix of adults, as a slower than normal recovery unfolds over the next decade or longer.”
“The decline in coral recruitment matches the extent of mortality of the adult brood stock in different parts of the Reef,” added Professor Hughes. “Areas that lost the most corals had the greatest declines in replenishment.”
“We expect coral recruitment will gradually recover over the next five to ten years, as surviving corals grow and more of them reach sexual maturity, assuming of course that we don’t see another mass bleaching event in the coming decade,” he said.
So far, the Great Barrier Reef has experienced four mass bleaching events due to global warming, in 1998, 2002, and back-to-back in 2016 and 2017. Scientists predict that the gap between pairs of coral bleaching events will continue to shrink as global warming intensifies.
“It’s highly unlikely that we could escape a fifth or sixth event in the coming decade,” said co-author Professor Morgan Pratchett.
“We used to think that the Great Barrier Reef was too big to fail – until now,” he said.
“For example, when one part was damaged by a cyclone, the surrounding reefs provided the larvae for recovery. But now, the scale of severe damage from heat extremes in 2016 and 2017 was nearly 1500km—vastly larger than a cyclone track.”
Professor Pratchett added that the southern reefs that escaped the bleaching are still in very good condition, but they are too far away to replenish reefs further north.
“There’s only one way to fix this problem,” says Hughes, “and that’s to tackle the root cause of global heating by reducing net greenhouse gas emissions to zero as quickly as possible.”
Hughes T, Kerry J, Baird A, Connolly S, Chase T, Dietzel A, Hill T, Hoey A, Hoogenboom M, Jacobson M, Kerswell A, Madin J, Mieog A, Paley A, Pratchett M, Torda G, & Woods R (2019). ‘Global warming impairs stock–recruitment dynamics of corals’. Nature: http://dx.doi.org/10.1038/s41586-019-1081-y
PHOTOS & VIDEO
A selection of photos and videos relating to the study is available here. Please note that any use of this imagery MUST carry the credit given. In addition, permission must be obtained from the ARC Centre of Excellence for Coral Reef Studies for any use beyond this story.
The Australian Academy of Science have produced a video based on the study. The files are available to embed in online stories at the Dropbox hyperlink above, and the YouTube embed link is here.
CONTACTS FOR INTERVIEWS
Prof Terry Hughes (Pacific Coast Time Zone, USA) Director, ARC Centre of Excellence for Coral Reef Studies Phone: +61 (0)400 720 164 Email: email@example.com
Prof Andrew Baird (Eastern Australia Time Zone) ARC Centre of Excellence for Coral Reef Studies Phone: +61 (0)7 4781 4857 Mobile: +61 (0)400 289 770 Email: firstname.lastname@example.org
Prof Morgan Pratchett (Eastern Australia Time Zone) ARC Centre of Excellence for Coral Reef Studies Phone: + 61 (0)7 4781 5747 Mobile: +61 (0)488 112 295 Email: email@example.com
FOR FURTHER INFORMATION
Melissa Lyne (Eastern Australia Time Zone) Media Manager, ARC Centre of Excellence for Coral Reef Studies Phone: +61 (0) 415 514 328 Email: firstname.lastname@example.org
We can fix the Great Barrier Reef
Leading coral reef scientists say Australia could restore the Great Barrier Reef to its former glory through better policies that focus on science, protection and conservation.
In a paper published in the journal Nature Climate Change, the authors argue that all the stressors on the Reef need to be reduced for it to recover.
An Australian Government report into the state of the Great Barrier Reef found that its condition in 2014 was “poor and expected to further deteriorate in the future”. In the past 40 years, the Reef has lost more than half of its coral cover and there is growing concern about the future impacts of ocean acidification and climate change.
“We need to move beyond the gloom and doom to identify how the decline of the Great Barrier Reef can be turned around,” says co-author Professor Terry Hughes from the ARC Centre of Excellence for Coral Reef Studies at James Cook University (JCU).
“Our paper shows that every major stressor on the Reef has been escalating for decades – more and more fishing, pollution, coastal development, dredging, and now for the past 20 years we’re also seeing the impacts of climate change.”
“We now have a very good handle on why the Great Barrier Reef is in trouble,” adds co-author, Jon Brodie from the Centre for Tropical Water and Aquatic Ecosystems Research at JCU.
“The challenge is to use that scientific knowledge to prevent further damage and give the Reef some breathing space that would allow it to recover.
Co-author, Jon Day, also from the ARC Centre for Coral Reef Studies at JCU says an obvious first step is to prevent unsustainable growth in each of the stressors to reduce their cumulative impact.
“If that means less dredging, less coal mining and more sustainable fishing, then that’s what Australia has to do. Business as usual is not an option because the values for which the Reef was listed as World Heritage are already deteriorating, and will only get worse unless a change in policy occurs.”
The authors say that as countries around the world move to curb global carbon emission, Australia has an opportunity to transition away from fossil fuels and to limit the development of huge coal ports alongside the Great Barrier Reef World Heritage Area.
“No-one is saying Queensland should not have ports – however, what we are saying is that all developments within, and adjacent to, the Great Barrier Reef need to be far more sustainable in the way that they are developed and operated, especially because they adjoin a World Heritage Area, “says Jon Day.
The authors agree that no one wants to see the Great Barrier Reef placed on UNESCO’s ‘World Heritage Area In-Danger’ list.
The Great Barrier Reef needs breathing space to recover. Image courtesy of State of Queensland
“The economic case for better protecting the Great Barrier Reef is very clear – it supports more than 60,000 jobs, mostly in Reef-related tourism,” says Professor Hughes.
The scientists have outlined a six-point plan they believe will restore the Great Barrier Reef, including;
A return to the former emphasis on conservation and protection of the Great Barrier Reef.
Australia taking a lead role in tackling climate change by transitioning away from fossil fuels.
Permanent legislative bans on dumping both capital and maintenance dredge spoil within the World Heritage area.
An overhaul of the environmental impact assessment process for new developments
The Great Barrier Reef Marine Park Authority (GBRMPA) reinstated as the agency responsible for all aspects of the Great Barrier Reef, including fishing and ports. A 50-year plan and adequate funding for the use of the catchment designed to reduce greenhouse gas emissions and agricultural run off.
Jon Brodie says Australia is starting to reduce runoff of nutrients, sediments and pesticides from land into the World Heritage Area, and is improving regulations for dumping capital dredge-spoil, but much more action is needed.
“These efforts are a welcome step in the right direction, but they will need much better resourcing in order to substantially reduce pressures on the World Heritage Area.”
The authors say the global community must make it clear that they want more effective policy action to ensure the Great Barrier Reef is restored for current and future generations.
“This paper raises awareness of the untapped opportunities to incorporate science into better policy to ensure we still have a magnificent Great Barrier Reef in the future,” Terry Hughes adds.