The window for saving the world’s coral reefs is rapidly closing
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.
“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.
The researchers show 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. When bleaching is severe and prolonged, many of the corals die. It takes at least a decade to replace even the fastest-growing species,” explained co-author Prof Andrew Baird of Coral CoE.
“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,” explained Prof Hughes. “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,” says Prof Hughes.
The paper “Spatial and temporal patterns of mass bleaching of corals in the Anthropocene” is now available here.
Associate Professor Julia Baum University of Victoria, Department of Biology
Victoria, BC CANADA
Phone: 1-250-858-9349 (PST/UTC -8)
Associate Professor Michael Berumen King Abdullah University of Science and Technology, Red Sea Research Center
Thuwal, SAUDI ARABIA
Phone: +966 544 700 019 (available from 3-4 Jan, MSK/UTC + 3; 5-7 Jan, CET/UTC + 1)
C. Mark Eakin, Ph. D. National Oceanic & Atmospheric Administration
Silver Spring, MD U.S.A.
Phone: 1-301-502-8608 (EST/UTC -5)
Prof Nicholas Graham Lancaster University, Lancaster Environment Centre
Lancaster, UNITED KINGDOM
Tel: +44 (0) 7479 438 914 (available from 4 Jan, GMT/UTC)
ARC Centre of Excellence for Coral Reef Studies at James Cook University
Townsville, QLD AUSTRALIA
Phone: +61 (0)7 4781 6067, +61 (0) 428 785 895 (AEST/UTC +10)
Taking stock of a thorny issue: 30 years of COTS research on the GBR
A new book exploring the best scientific research on preventing coral-eating Crown-Of-Thorns Starfish (COTS) outbreaks, is expected to become a critical resource for informing management of these outbreaks across the Indo-Pacific.
Prof Pratchett’s research over the past two decades has contributed significantly to understanding the causes and consequences of outbreaks.
He describes COTS outbreaks as `akin to locusts’ and said there was still much to learn.
“Outbreaks occur on many reefs throughout the Indo-Pacific, including the Great Barrier Reef, and contribute to the widespread degradation of these valuable ecosystems,” Prof Pratchett said.
“Despite significant research on the biology and ecology of COTS, there are still some considerable knowledge gaps and opportunities for important discoveries.
“More than a thousand research papers have been written about these animals, reflecting the ecological impact and management concern surrounding COTS outbreaks.”
Dr Uthicke, a biologist and geneticist, is focussed on the development of new genetic tools (eDNA) to gain insights into the early life-history of COTS.
He said researchers needed to embrace new technologies and opportunities to advance our understanding of COTS biology and behaviour.
“We must focus on key questions that will improve management effectiveness in reducing the frequency and likelihood of outbreaks, if not preventing them altogether,” Dr Uthicke said.
“There is still a lot we do not know about these starfish and effective management is conditional upon improved knowledge of their biology, especially during the very early life stages, when the starfish are extremely small and very cryptic.”
The Special Issue “Biology, Ecology and Management of Crown-of-Thorns Starfish” is published in the journal Diversity and now available open access with MDPI books.
Please note, images must carry credits as listed in Dropbox folder here.
ARC Centre of Excellence for Coral Reef Studies, James Cook University
Phone: +61 0428 785 895 or +61 07 4781 6067 (GMT +10)
Two-thirds of Great Barrier Reef hit by back-to-back mass coral bleaching
For the second time in just 12 months, scientists have recorded severe coral bleaching across huge tracts of the Great Barrier Reef after completing aerial surveys along its entire length. In 2016, bleaching was most severe in the northern third of the Reef, while one year on, the middle third has experienced the most intense coral bleaching.
“The combined impact of this back-to-back bleaching stretches for 1,500 km (900 miles), leaving only the southern third unscathed,” says Prof. Terry Hughes, Director of the ARC Centre of Excellence for Coral Reef Studies, who undertook the aerial surveys in both 2016 and 2017.
“The bleaching is caused by record-breaking temperatures driven by global warming. This year, 2017, we are seeing mass bleaching, even without the assistance of El Niño conditions.”
The aerial surveys in 2017 covered more than 8,000 km (5,000 miles) and scored nearly 800 individual coral reefs closely matching the aerial surveys in 2016 that were carried out by the same two observers.
Dr. James Kerry, who also undertook the aerial surveys, explains further, “this is the fourth time the Great Barrier Reef has bleached severely – in 1998, 2002, 2016, and now in 2017. Bleached corals are not necessarily dead corals, but in the severe central region we anticipate high levels of coral loss.”
“It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016.”
Coupled with the 2017 mass bleaching event, Tropical Cyclone Debbie struck a corridor of the Great Barrier Reef at the end of March. The intense, slow-moving system was likely to have caused varying levels of damage along a path up to 100 km in width. Any cooling effects related to the cyclone are likely to be negligible in relation to the damage it caused, which unfortunately struck a section of the reef that had largely escaped the worst of the bleaching.
“Clearly the reef is struggling with multiple impacts,” explains Prof. Hughes. “Without a doubt the most pressing of these is global warming. As temperatures continue to rise the corals will experience more and more of these events: 1°C of warming so far has already caused four events in the past 19 years.”
“Ultimately, we need to cut carbon emissions, and the window to do so is rapidly closing.”
Key graphic 2016 -2017_GBRbleaching.jpg (high and low res versions available)
This composite map shows surveyed coral reefs in 2016 (left panel) and 2017 (right panel).
Not all data is shown, only reefs at either end of the bleaching spectrum: Red circles indicate reefs undergoing most severe bleaching (60% or more of visible corals bleaching) Green circles indicate reefs with no or only minimal bleaching (10% or less of corals bleaching).
Prof. Terry Hughes
Director, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0)400 720 164, +61 (0)7 4781 4000
Dr. James Kerry
Senior Research Officer, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0)407 475 576, +61 (0)7 4781 4823
Prof. Sean Connolly
Chief Investigator, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0)7 4781 4242
Communications Manager, ARC Centre of Excellence for Coral Reef Studies
Phone: +61 (0)415 514 328
Note for editors
The two observers: Prof Terry Hughes and Dr. James Kerry work at the ARC Centre of Excellence for Coral Reef Studies at James Cook University in Townsville, Australia. The Centre for World University Rankings recently ranked this institution number 1 globally for Marine and Freshwater biology research.
The aerial survey techniques used in this study were employed consistently in all four bleaching events on the Great Barrier Reef: 1998, 2002, 2016 and 2017. They were backed up by extensive in-water research during the 2016 event and published in the peer-reviewed journal, Nature. (Link to journal)
Coral bleaching occurs when abnormal environmental conditions, like heightened sea temperatures, cause corals to expel tiny photosynthetic algae, called ‘zooxanthellae’. The loss of these colorful algae causes the corals to turn white, and bleach͛. Bleached corals can recover if the temperature drops and zooxanthellae are able to recolonise them, otherwise the coral may die.
In the six months following the peak of bleaching in March 2016, scientists measured on average 67% loss of corals in the northern 700 km section of the Great Barrier Reef, which was the worst impacted section in that year. An interactive map of images and video of aerial survey footage from the 2016 event can be found here.
Greater protection needed for Great Barrier Reef’s magnificent table corals
Scientists at the ARC Centre of Excellence for Coral Reef Studies at James Cook University say more needs to be done to protect vulnerable table corals on the Great Barrier Reef.
Researchers studying the role of table corals have found that they provide vital sun protection for large fish in shallow reef areas.
They found that the corals are so important that if lost, the fish that depend on them will leave the reef.
“The loss of table corals denies fishes important habitat, which they use to shelter from the sun, avoiding harmful UV-radiation, just as we might sit under an umbrella at the beach,” says study lead author James Kerry.
“Large fishes maintain balanced coral reef ecosystems, they’re the predators that help control fish populations,” says study co-author Professor David Bellwood.
Table corals are particularly vulnerable – and are the preferred meal of the Crown of Thorns Starfish. Credits: James Kerry
“These fish are important for reefs and people; lose your table corals and you lose your coral trout,” Professor Bellwood explains.
The scientists say this is particularly concerning as table corals are especially vulnerable to the pressures currently facing the Great Barrier Reef.
The corals are highly susceptible to ocean acidification and bleaching, and are the preferred meal of the destructive crown of thorns starfish.
Given their shape, table corals are also easily toppled and are often destroyed in cyclones.
“Ultimately we need to conserve table corals because they are the primary structure on the Reef that provides shelter from the sun’s harmful rays. However, because they are so vulnerable to climate change and other growing threats, this is going to be a major challenge,” James Kerry says.
“The research suggests that we need to do everything we can to promote the health of the Great Barrier Reef, and in doing so, reduce the multiple threats facing these valuable corals.”
Great Barrier Reef marine reserves combat coral disease
A new and significant role for marine reserves on the Great Barrier Reef has been revealed, with researchers finding the reserves reduce the prevalence of coral diseases.
It’s been known for some time that marine reserves are important for maintaining and enhancing fish stocks, but this is the first time marine reserves have been shown to enhance coral health on the Great Barrier Reef.
Researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University found that coral disease levels were four times lower inside no-take marine reserves, where fishing is banned, compared to outside reserves.
Discarded fishing line caught on Great Barrier Reef coral. Image: Joleah Lamb.
“We surveyed more than 80,000 corals around the Whitsunday Islands for six different diseases that commonly harm reef corals around the world,” says study lead author, Dr Joleah Lamb from the Coral CoE.
“We found three coral diseases were more prevalent on reefs outside no-take marine reserves, particularly on reefs with high levels of injured corals and discarded fishing line.”
Wounded corals are more vulnerable to disease. Damaged tissue provides sites where pathogens and parasites can invade, particularly as coral immune responses are lowered while they heal.
Dr Lamb says once a pathogen infects a coral, tissue loss typically spreads from the point of entry.
“It’s like getting gangrene on your foot and there is nothing you can do to stop it from affecting your leg and ultimately your whole body.”
“Disease outbreaks can take a heavy toll, with losses of up to 95 per cent of coral cover on some reefs in the Caribbean.”
Given the difficulty identifying pathogens that cause disease, the researchers say it’s vital to understand which activities increase the risk of coral diseases, and to protect against them.
They say discarded fishing line and levels of coral breakage, potentially from a variety of fishing-related activities, outside the no-take zones on the Great Barrier Reef are indicators of the types of activities that contribute to the problem.
Researchers survey coral on the Great Barrier Reef. Image: Joleah Lamb.
“Fishing line not only causes coral tissue injuries and skeleton damage, but also provides an additional surface for potential pathogens to colonise, increasing their capacity to infect wounds caused by entangled fishing line,” Dr Lamb says.
The researchers hope their findings send a clear message to reef managers about the benefits of marine reserves for coral health.
“No take marine reserves are a promising approach for mitigating coral disease in locations where the concentration or intensity of fishing effort is relatively high,” says Professor Garry Russ from the Coral CoE.
Professor Bette Willis, also from the Coral CoE, says the scientists are now expanding their research to examine other drivers of coral disease.
“We’ve shown that there are strong links between damage and disease in this study, now we’re interested in understanding and managing other potential drivers of diseases that involve injury– such as outbreaks of crown-of-thorns starfish, cyclones, and recreational activities like anchoring.”
Paper: Lamb JB, Williamson DH, Russ GR, and BL Willis (In Press). Protected areas mitigate diseases of reef-building corals by reducing damage from fishing. Ecology. DOI:10.1890/14-1952.1
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.
Twice the coral trout in Great Barrier Reef protected zones
Coral trout in protected ‘green zones’ are not only bigger and more abundant than those in fished ‘blue zones’ of the Great Barrier Reef Marine Park, but they are also better able to cope with cyclone damage, according to a long-term study published today in Current Biology.
Coral trout biomass has more than doubled since the 1980s in the green zones with most of the growth occurring since the 2004 rezoning. These and other changes identified by the study show that the green zones are contributing to the health of the Great Barrier Reef and that similar approaches may be beneficial for coral reefs around the world.
The joint project between the Australian Institute of Marine Science and the ARC Centre of Excellence for Coral Reef Studies at James Cook University combined a vast amount of information from underwater surveys carried out from 1983-2012, on reefs spread across approximately 150,000 km2 (more than 40 per cent) of the Marine Park.
The Marine Park was rezoned in 2004, and marine reserves where fishing is prohibited (called ‘green zones’ because of their colour on the zoning maps of the Marine Park), were expanded to cover about one-third of the total Park area. These green zones previously made up less than five percent of the Park.
The study demonstrated that the Reef’s network of green zones are yielding wide-scale population increases for coral trout, the primary target species of both the commercial and recreational sectors of the hook-line fishery.
It also found that reefs in green zones supported higher numbers of large, reproductively-mature coral trout, even after being damaged by cyclones—such as tropical cyclone Hamish, which hit the reef in 2009.
The findings provide compelling evidence that effective protection within green zone networks can play a critical role in conserving marine biodiversity and enhancing the sustainability of targeted fish populations.
“It’s heartening to know the green zones are working as we had expected,” said lead author Michael Emslie from AIMS.
“Among the world’s coral reefs, fishing on the Great Barrier Reef is relatively light but it has still reduced the number and average size of the few fish species that are taken by fishers. Data since the 1980s show that green zones have been effective in restoring numbers of coral trout to their former levels”.
David Williamson, a co-author from the ARC Centre of Excellence for Coral Reef Studies said “We expected to see some declines in coral trout biomass on reefs that remained open to fishing after the rezoning due to the increased concentration of fishing effort on those reefs, a so-called ‘squeeze effect’. Instead we found that coral trout biomass remained stable on fished reefs in areas that avoided the impacts of Cyclone Hamish, while it increased significantly on green zone reefs. Ultimately it has led to an overall increase in coral trout biomass across those regions. It’s a really positive result for both the fish and the fishery.”
The study suggests that the original Marine Park zoning plan that was put in place in the 1980s began to improve fish stocks, but that the expanded protection in 2004 greatly improved on this.
Hugh Sweatman, also of AIMS and co-author of the paper, said “Australia’s Great Barrier Reef Marine Park is looked upon as a benchmark for large-scale reserve networks around the world. Unlike many places where coral reefs are found, Australia is a developed country where fishing is fairly light and well regulated. Yet even here we see clear effects of fishing – the benefits of no-take reserves would be much more obvious where large coastal populations depend on reefs for their daily food, so fishing is more intense and everything is taken.
The details of our findings suggest that effectively protected networks of no-take reserves will help reef fishes cope with some present and future stresses, and assist in maintaining coral reef fish populations as we know them.”