Paul Hardisty, Australian Institute of Marine Science; Christian Roth, CSIRO; Damien Burrows, James Cook University; David Mead, Australian Institute of Marine Science; Ken Anthony, Australian Institute of Marine Science; Line K Bay, Australian Institute of Marine Science; Mark Gibbs, Queensland University of Technology, and Peter J Mumby, The University of Queensland
Scientists recently confirmed the Great Barrier Reef suffered another serious bleaching event last summer – the third in five years. Dramatic intervention to save the natural wonder is clearly needed.
First and foremost, this requires global greenhouse gas emissions to be slashed. But the right combination of technological and biological interventions, deployed with care at the right time and scale, are also critical to securing the reef’s future.
This could include methods designed to shade and cool the reef, techniques to help corals adapt to warmer temperatures, ways to help damaged reefs recover, and smart systems that target interventions to the most strategically beneficial locations.
Implementing such measures across the breadth of the reef – the world’s biggest reef ecosystem – will not be easy, or cheap. In fact, we believe the scale of the task is greater than the Apollo 11 Moon landing mission in 1969 – but not impossible.
That mission was a success, not because a few elements worked to plan, but because of the integration, coordination and alignment of every element of the mission’s goal: be the first to land and walk on the Moon, and then fly home safely.
Half a century later, facing the ongoing decline of the Great Barrier Reef, we can draw important lessons from that historic human achievement.
The recently released Reef Restoration and Adaptation Program concept feasibility study shows Australia could feasibly, and with reasonable probability of success, intervene to help the reef adapt to and recover from the effects of climate change.
The study, of which we were a part, involved more than 100 leading coral reef scientists, modellers, economists, engineers, business strategists, social scientists, decision scientists and reef managers.
It shows how new and existing interventions, supported by the best available research and development, could help secure a future for the reef.
We must emphasise that interventions to help the reef adapt to and recover from climate change will not, alone, save it. Success also depends on reducing global greenhouse emissions as quickly as possible. But the hands-on measures we’re proposing could help buy time for the reef.
Our study identified 160 possible interventions that could help revive the reef, and build on its natural resilience. We’ve whittled it down to the 43 most effective and realistic.
Possible interventions for further research and development include brightening clouds with salt crystals to shade and cool corals; ways to increase the abundance of naturally heat-tolerant corals in local populations, such as through aquarium-based selective breeding and release; and methods to promote faster recovery on damaged reefs, such as deploying structures designed to stabilise reef rubble.
But there will be no single silver bullet solution. The feasibility study showed that methods working in combination, along with water quality improvement and crown-of-thorns starfish control, will provide the best results.
There are four reasons why saving the Great Barrier Reef in coming decades could be more challenging than the 1969 Moon mission.
First, warming events have already driven the reef into decline with back-to-back bleaching events in 2016 and 2017, and now again in 2020. The next major event is now only just around the corner.
Second, current emission reduction pledges would see the world warm by 2.3-3.5℃ relative to pre-industrial levels. This climate scenario, which is not the worst case, would be beyond the range that allows today’s coral reef ecosystems to function.
Without swift action, the prospect for the world’s coral reefs is bleak, with most expected to become seriously degraded before mid-century.
And fourth, the inherent complexity of natural systems, particularly ones as diverse as coral reefs, provides an additional challenge not faced by NASA engineers 50 years ago.
So keeping the Great Barrier Reef, let alone the rest of the world’s reefs, safe from climate change will dwarf the challenge of any space mission. But there is hope.
The federal government recently re-announced A$100 million from the Reef Trust Partnership towards a major research and development effort for this program. This will be augmented by contributions of A$50m from research institutions, and additional funding from international philanthropists.
Our study shows that under a wide range of future emission scenarios, the program is very likely to be worth the effort, more so if the world meets the Paris target and rapidly cuts greenhouse gas emissions.
What’s more, economic analyses included in the feasibility study show successful Great Barrier Reef intervention at scale could create benefits to Australia of between A$11 billion and A$773 billion over a 60-year period, with much of it flowing to regional economies and Traditional Owner communities.
And perhaps more importantly, if Australia is successful in this effort, we can lead the world in a global effort to save these natural wonders bequeathed to us across the ages. We must start the journey now. If we wait, it may be too late.
The authors gratefully acknowledge the contribution of David Wachenfeld, Chief Scientist of the Great Barrier Reef Marine Park Authority and member of the the steering committee for the development of this program.
Paul Hardisty, CEO, Australian Institute of Marine Science; Christian Roth, CSIRO Great Barrier Reef Coordinator & Senior Principal Research Scientist, CSIRO; Damien Burrows, Director of TropWATER, James Cook University; David Mead, Executive Director of Strategic Development at Australian Institute of Marine Science, Australian Institute of Marine Science; Ken Anthony, Principal Research Scientist, Australian Institute of Marine Science; Line K Bay, Senior Research Scientist and Team Leader, Australian Institute of Marine Science; Mark Gibbs, Director, Knowledge to Innovation; Chair, Green Cross Australia, Queensland University of Technology, and Peter J Mumby, Chair professor, The University of Queensland
The Australian summer just gone will be remembered as the moment when human-caused climate change struck hard. First came drought, then deadly bushfires, and now a bout of coral bleaching on the Great Barrier Reef – the third in just five years. Tragically, the 2020 bleaching is severe and the most widespread we have ever recorded.
Coral bleaching at regional scales is caused by spikes in sea temperatures during unusually hot summers. The first recorded mass bleaching event along Great Barrier Reef occurred in 1998, then the hottest year on record.
Since then we’ve seen four more mass bleaching events – and more temperature records broken – in 2002, 2016, 2017, and again in 2020.
This year, February had the highest monthly sea surface temperatures ever recorded on the Great Barrier Reef since the Bureau of Meteorology’s records began in 1900.
We surveyed 1,036 reefs from the air during the last two weeks in March, to measure the extent and severity of coral bleaching throughout the Great Barrier Reef region. Two observers, from the ARC Centre of Excellence for Coral Reef Studies and the Great Barrier Reef Marine Park Authority, scored each reef visually, repeating the same procedures developed during early bleaching events.
The accuracy of the aerial scores is verified by underwater surveys on reefs that are lightly and heavily bleached. While underwater, we also measure how bleaching changes between shallow and deeper reefs.
Of the reefs we surveyed from the air, 39.8% had little or no bleaching (the green reefs in the map). However, 25.1% of reefs were severely affected (red reefs) – that is, on each reef more than 60% of corals were bleached. A further 35% had more modest levels of bleaching.
Bleaching isn’t necessarily fatal for coral, and it affects some species more than others. A pale or lightly bleached coral typically regains its colour within a few weeks or months and survives.
But when bleaching is severe, many corals die. In 2016, half of the shallow water corals died on the northern region of the Great Barrier Reef between March and November. Later this year, we’ll go underwater to assess the losses of corals during this most recent event.
Compared to the four previous bleaching events, there are fewer unbleached or lightly bleached reefs in 2020 than in 1998, 2002 and 2017, but more than in 2016. Similarly, the proportion of severely bleached reefs in 2020 is exceeded only by 2016. By both of these metrics, 2020 is the second-worst mass bleaching event of the five experienced by the Great Barrier Reef since 1998.
The unbleached and lightly bleached (green) reefs in 2020 are predominantly offshore, mostly close to the edge of the continental shelf in the northern and southern Great Barrier Reef. However, offshore reefs in the central region were severely bleached again. Coastal reefs are also badly bleached at almost all locations, stretching from the Torres Strait in the north to the southern boundary of the Great Barrier Reef Marine Park.
For the first time, severe bleaching has struck all three regions of the Great Barrier Reef – the northern, central and now large parts of the southern sectors. The north was the worst affected region in 2016, followed by the centre in 2017.
In 2020, the cumulative footprint of bleaching has expanded further, to include the south. The distinctive footprint of each bleaching event closely matches the location of hotter and cooler conditions in different years.
Of the five mass bleaching events we’ve seen so far, only 1998 and 2016 occurred during an El Niño – a weather pattern that spurs warmer air temperatures in Australia.
But as summers grow hotter under climate change, we no longer need an El Niño to trigger mass bleaching at the scale of the Great Barrier Reef. We’ve already seen the first example of back-to-back bleaching, in the consecutive summers of 2016 and 2017. The gap between recurrent bleaching events is shrinking, hindering a full recovery.
After five bleaching events, the number of reefs that have escaped severe bleaching continues to dwindle. Those reefs are located offshore, in the far north and in remote parts of the south.
The Great Barrier Reef will continue to lose corals from heat stress, until global emissions of greenhouse gasses are reduced to net zero, and sea temperatures stabilise. Without urgent action to achieve this outcome, it’s clear our coral reefs will not survive business-as-usual emissions.
For some years, Australia has been on notice: the world is watching how we care for the Great Barrier Reef. The iconic natural wonder is the largest living organism on the planet. But its health is deteriorating.
In 2017 UNESCO, the United Nations body that granted the reef world heritage status, asked Australia to report back on how the reef was faring.
Australia this month submitted its latest report. It provides a wealth of information on many threats to the reef, such as water quality and crown-of-thorns starfish.
But the report’s overall message is that the reef’s world heritage values are fine and the threats are in hand, when the reality is far different.
The Great Barrier Reef was listed as a World Heritage Area in 1981. It was recognised as globally significant or, in the parlance of the world heritage committee, having “outstanding universal value”.
In ensuing years, a myriad of impacts have devastated the reef’s health. They include coral bleaching exacerbated by climate change, poor water quality from land-based runoff, and unsustainable fishing and coastal development.
UNESCO considered listing the reef as “in danger” but in 2017 decided against it. Australia was asked to report back to show it was protecting the reef’s outstanding universal value.
But Australia’s report is deficient. It claims the reef “maintains many of the elements” that make up its outstanding universal value – yet its methodology fails to properly assess this.
The report relies on assessments made by the Great Barrier Reef Marine Park Authority in its five-yearly outlook report released in August. Our analysis shows four flaws in that otherwise commendable report have carried over to the report to UNESCO.
First, instead of assessing the world heritage values themselves, the report assessed the four natural criteria for which the reef was granted world heritage status.
These four broad criteria cover the reef’s exceptional natural beauty; its evolution over millennia; its outstanding demonstration of significant ecological and biological processes; and its enormous biodiversity of habitats and species.
Each of these criteria comprise many “values”, or features. The outlook report assesses the status and trends of these values but fails to identify which are specifically world heritage values – which is what UNESCO really needs to know.
Here’s an example. The biodiversity criterion encompasses coral reefs, sandy and muddy habitats, mangroves and seagrass, dugongs, whales, dolphins, turtles and birds.
For biodiversity, the report gives an overall grade of “poor”. But this obscures the fact large areas of coral – a key world heritage value – are in very poor health.
This method is used despite the federal government’s own legislation specifically requiring the reef’s world heritage values, not the criteria, be assessed.
Second, the latest assessment is measured against results in 2014. So it does not show the degradation since the reef was listed 38 years ago.
Third, the report wrongly assesses the reef’s “integrity”, an important part of its outstanding universal value. Integrity refers to the “wholeness and intactness” of the area and its threats, and requires separate investigation. Instead, the report assumes the assessments of the criteria answer the integrity question.
Fourth, both reports fail to acknowledge Indigenous people’s links to the reef are clearly part of its outstanding universal value.
In essence, the report to UNESCO sends the message Australia is well in control of the threats to the reef. This is misleading, and does not accord with the 2019 outlook report which downgraded the reef’s prospects from “poor” to “very poor”.
These criticisms may seem semantic. But the report will be critical when the world heritage committee meets next year in China to assess how the reef is faring.
The table below demonstrates a more logical and relevant way of reporting back to UNESCO. Information in the outlook report is rearranged in this example against one of four world heritage criteria.
If a summary against all four criteria, plus integrity, is necessary, it would be better presented as per the table below showing the grades and trends of all relevant values.
Problems with the government’s report to UNESCO extend beyond the issues outlined above. The government acknowledges climate change is the biggest threat to the reef, and limiting temperature rise to 1.5℃ this century is widely accepted as the critical threshold for reef survival.
But the government’s report fails to explain how Australia is reducing emissions in line with this goal. A recent analysis suggests if Australia’s efforts were matched globally, warming would not be kept within 2°C, let alone 1.5°C.
Without clear and unambiguous information, the world heritage committee cannot draw an informed conclusion about whether the Great Barrier Reef should be listed as “in danger”. The listing would not fix the problems – but it might force Australia to act.
Correction: a previous version of Table 2 in this report contained outdated figures for the category “Habitats for conserving biodiversity”. The figures have been corrected.
Few feel the pain of the Great Barrier Reef’s decline more acutely than the scientists trying to save it. Ahead of next week’s UN climate summit, two researchers write of their grief, and hope.
Professorial Fellow, ARC Centre of Excellence for Coral Reef Studies, James Cook University
As I write this, much of inland eastern Australia is enduring what is likely to be the worst drought ever recorded. Bushfires are devastating parts of New South Wales and southern Queensland, tearing through rainforest that should not be dry enough to burn. Major towns will probably soon run out of water. The condition of the vital Murray-Darling river system is dire.
Some federal government MPs have responded by questioning whether these events are linked to anthropogenic, or man-made, climate change. Others deny the science outright. Now we have a politically motivated Senate inquiry into water quality on the Great Barrier Reef.
This situation brings me to despair. For the past 45 years I have researched and managed coral reef water quality in Australia and overseas. Now 72, I see that much of my work, and that of my colleagues, has not led to a bright future for coral reefs. In decades to come they will probably still contain some corals, but ecologically speaking they will not be growing, or even functioning.
Official assessments appear to confirm the reef’s inexorable demise. A five-yearly outlook report from the Great Barrier Reef Marine Park Authority this month declared the outlook was “very poor” – a decline from “poor” in 2014. A joint federal-Queensland government report released on the same day found “minimal progress” in addressing water quality – the second most serious threat to the reef.
The United Nations Intergovernmental Panel on Climate Change warned in October last year that a global temperature rise of 2℃ above pre-industrial levels will decimate coral growth. It said we must stay below 1.5℃ of warming for coral reefs to have a reasonable chance for a future.
I feel guilty when discussing this situation with young scientists. I worry that my legacy is such that they will spend their professional lives studying and documenting the terminal decline of coral reefs.
I feel the same sense of guilt towards my 19-year-old grandson, who is in his first year of university studying mathematics. The outlook is grim, not just for coral reefs but for society in general.
My life’s work, spent mostly outside, has taken a toll on my health. I’ve had several skin cancers excised over the past 25 years and in recent years have undergone major skin cancer surgery. I have recovered well and still come to James Cook University every day. But the combination of ill-health, coupled with political inaction over the dire state of the environment, only compounds a feeling that I can’t really make a difference anymore.
But on a more positive note, the Great Barrier Reef is more than just coral. It includes a wonderful array of seagrass, dugongs, turtles, fish, dolphins, birds, and whales – and this is not a complete list.
Many of these species are also in decline. But good water quality management will, for example, help encourage the growth of seagrass on which dugongs and green turtles rely for food. The overall picture may be grim, but there are small spots of hope.
Assistant Director, ARC Centre of Excellence for Coral Reef Studies, James Cook University
I spent last weekend on Magnetic Island, just a short ferry ride from my Townsville home. With great joy I sat with our infant under a beach tent and watched my older son happily snorkel among the corals and fish.
The intergenerational inequalities posed by climate change have become all the more real since I became a mum. The reef my son swam over is fundamentally different from reefs that existed when my parents were children, and they are continuing to change.
As the wet season approaches, my anxiety, and that of my colleagues, increases at the prospect of another extreme marine heatwave. Two consecutive summers of coral bleaching in 2016 and 2017 severely damaged two-thirds of the Great Barrier Reef. Some researchers who bore witness to these events experienced “ecological grief”: a profound sense of loss at the environmental harm that global warming brings.
In much the same way, a large proportion of north Queensland residents and tourists experience significant grief associated with coral bleaching and mortality. Biodiversity loss also affects Traditional Owners, impacting their connection to Sea Country.
Extreme weather events associated with climate change jeopardise the tourism and fishing industries, and coastal infrastructure that underpin the region’s economy. Insurance premiums are already higher in northern Australia than in the rest of the country, and some places may one day become uninsurable.
However, my children were born in a wealthy country that is likely to withstand and recover from climate impacts that affect their basic needs. This privilege is not shared by the majority of reef-dependent coastal communities in the world’s tropics.
I come from a family of healthcare professionals, but felt a career in environmental science offered the potential to make a broader impact. The state of the planet and human health and well-being are inextricably linked.
I continue to be motivated by my research on the Great Barrier Reef. But I am deeply concerned about rising mistrust in the scientific process, despite unequivocal evidence of the reef’s decline and the impacts of climate change. It is particularly distressing when members of the federal government undermine the science that informs their own policies – including North Queensland politicians advocating for a national watchdog to verify scientific papers.
If our political leaders want to support community adaptation and resilience to climate change, they should build, rather than erode, public trust in the evidence that underpins reef management and policy.
This piece is part of Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.
Jon Brodie, Professorial Fellow, ARC Centre of Excellence for Coral Reef Studies, James Cook University and Alana Grech, Assistant Director, ARC Centre of Excellence for Coral Reef Studies, James Cook University
When the managers of the Great Barrier Reef recently rated its outlook as very poor, a few well-known threats dominated the headlines. But delve deeper into the report and you’ll find that this global icon is threatened by a whopping 45 risks.
However, many of the 45 threats are not well known or understood. All but two are happening now – and most are steadily getting worse. Collectively, it means the Great Barrier Reef is heading for a “death by a thousand cuts”.
The Great Barrier Reef Marine Park Authority produced the 2019 Outlook Report, required by law every five years. It shows the total number of threats has increased from 41 in 2014 to 45 now.
All of these threaten the Great Barrier Reef’s World Heritage values – the factors that make it globally outstanding. Of the 45 threats, 42 threaten its remarkable ecosystem.
The new threats include the loss of cultural knowledge, especially by the Indigenous traditional owners, and the potential negative impacts of genetic modification which are not well understood but could occur when modified organisms are released into the wild.
The table below shows the most alarming 21 risks to the Great Barrier Reef ecosystem. It is becoming clear that many of the risks are serious, and the situation is getting worse.
The likelihood and consequences of many lesser known threats are increasing.
The ten threats leading to “very high” risks are of greatest concern, especially as all are considered “almost certain” to occur. They include:
• The modification of coastal habitats from continued urban and industrial development. Vegetation clearing damages important ecosystem services for many marine species.
• Illegal fishing and poaching elsewhere are impacting global fish stocks. This will increase the incentive for such activity on the Great Barrier Reef, with major consequences for some species and habitats.
• Altered weather patterns are predicted as climate change accelerates, including more frequent and/or intense cyclones, floods and heatwaves. These weather events are natural processes in tropical regions, but when severe can prolong recovery times of coral ecosystems by up to 20 years.
At least 6 of the 11 “high” risks are worsening, including:
• Disease outbreaks in corals, turtles and coral trout were of “minor” consequence in 2009 but “major” consequence in 2019.
• The likelihood of altered ocean currents and their flow-on effects has been revised from “unlikely” in 2014 to “almost certain” in 2019. An increase in speed and the southern extent of the East Australian Current has already been observed. Such changes could irreversibly affect how eggs, larvae and juvenile organisms are naturally distributed.
• The likelihood of problems from artificial light emitted from shipping and coastal development has increased from “likely” in 2014 to “almost certain” in 2019. This is known to affect turtle hatchlings and may be detrimental to seabirds and fish behaviour.
Many of the threats to the reef ecosystem occur simultaneously, and can act together to exacerbate the impacts. These cumulative effects are not all well understood and have not been adequately addressed in the Outlook Report, so this is further cause for concern.
We cannot forget the problems that loom largest for the Great Barrier Reef: climate change and poor water quality.
The report rates the potential consequences of climate change-related sea temperature increase and ocean acidification as catastrophic.
• Ocean acidification (decreasing ocean pH levels) is reducing the capacity of corals and other calcifying organisms to build skeletons and shells, which reduces their capacity to create habitat.
The federal government is failing to meaningfully address Australia’s contribution to climate change, especially as the scale of the problem is much greater than the scale of interventions to date.
Runoff containing sediment, nutrients and pesticides, mainly from agriculture, is causing poor water quality which can stifle the growth of coral and seagrass, and encourage outbreaks of the damaging crown-of-thorns starfish.
Despite substantial investment of human and financial resources to address the problem, the Queensland Government’s latest water quality report card this month gave the reef a rating of “D” overall and warned that high sediment loads “will continue to be transported to, and remain in, the region”.
It is clear that despite management efforts at local, regional and national levels, a significant number of threats to the reef are getting worse. The evidence leading to the ‘derived trend’ arrows on the right-hand side of the above table indicates ongoing concerns.
Much more effort is required to effectively address complex threats such as climate change. But to ensure that the Great Barrier Reef survives as a healthy, resilient ecosystem, we must also ensure the lesser known risks are addressed.
This requires greater efforts by the community, industries, traditional owners and non-government organisations together with strong leadership from governments and their agencies. Unless this happens, the prognosis for the Great Barrier Reef is worse than “very poor” – and the ecological, social, economic and cultural impacts of that will be devastating.
Support for the aerial images by Matt Curnock was provided by TropWATER JCU, the Marine Monitoring Program – Inshore Water Quality through the Great Barrier Reef Marine Park Authority, the Queensland Government, the Landholders Driving Change project led by NQ Dry Tropics, CSIRO and the National Environmental Science Program Tropical Water Quality Hub.
It’s official. The outlook for the Great Barrier Reef has been downgraded from “poor” to “very poor” by the Australian government’s own experts.
That’s the conclusion of the latest five-yearly report from the Great Barrier Reef Marine Park Authority, released on Friday. The report assessed literally hundreds of scientific studies published on the reef’s declining condition since the last report was published in 2014.
The past five years were a game-changer. Unprecedented back-to-back coral bleaching episodes in 2016 and 2017, triggered by record-breaking warm sea temperatures, severely damaged two-thirds of the reef. Recovery since then has been slow and patchy.
Looking to the future, the report said “the current rate of global warming will not allow the maintenance of a healthy reef for future generations […] the window of opportunity to improve the reef’s long-term future is now”.
But that window of opportunity is being squandered so long as Australia’s and the world’s greenhouse gas emissions continue to rise.
A logical national response to the outlook report would be a pledge to curb activity that contributes to global warming and damages the reef. Such action would include a ban on the new extraction of fossil fuels, phasing out coal-fired electricity generation, transitioning to electrified transport, controlling land clearing and reducing local stressors on the reef such as land-based runoff from agriculture.
But federal Environment Minister Sussan Ley’s response to the outlook report suggested she saw no need to take dramatic action on emissions, when she declared: “it’s the best managed reef in the world”.
The federal government’s lack of climate action was underscored by another dire report card on Friday. Official quarterly greenhouse gas figures showed Australia’s greenhouse gas emissions have risen to the highest annual levels since the 2012-13 financial year.
But rather than meaningfully tackle Australia’s contribution to climate change, the federal government has focused its efforts on fixing the damage wrought on the reef. For example as part of a A$444 million grant to the Great Barrier Reef Foundation, the government has allocated $100 million for reef restoration and adaptation projects over the next five years or so.
Solutions being supported by the foundation include a sunscreen-like film to float on the water to prevent light penetration, and gathering and reseeding coral spawn Separately, Commonwealth funds are also being spent on projects such as giant underwater fans to bring cooler water to the surface.
But the scale of the problem is much, much larger than these tiny interventions.
The second biggest impact on the Great Barrier Reef’s health is poor water quality, due to nutrient and sediment runoff into coastal habitats. Efforts to address that problem are also going badly.
This was confirmed in a confronting annual report card on the reef’s water quality, also released by the Commonwealth and Queensland governments on Friday.
It showed authorities have failed to reach water quality targets set under the Reef 2050 Plan – Australia’s long-term plan for improving the condition of the reef.
For example the plan sets a target that by 2025, 90% of sugarcane land in reef catchments should have adopted improved farming practices. However the report showed the adoption had occurred on just 9.8% of land, earning the sugarcane sector a grade of “E”.
The 2019 outlook report and other submissions from Australia will be assessed next year when the UNESCO World Heritage Committee meets to determine if the Great Barrier Reef should be listed as “in danger” – an outcome the federal government will fight hard to avoid.
An in-danger listing would signal to the world that the reef was in peril, and put the federal government under greater pressure to urgently prevent further damage. Such a listing would be embarrassing for Australia, which presents itself as a world’s-best manager of its natural assets.
The outlook report maintains that the attributes of the Great Barrier Reef
that led to its inscription as a world heritage area in 1981 are still intact, despite the loss of close to half of the corals in 2016 and 2017.
But by any rational assessment, the Great Barrier Reef is in danger. Most of the pressures on the reef are ongoing, and some are escalating – notably anthropogenic heating, also known as human-induced climate change.
And current efforts to protect the reef are demonstrably failing. For example despite an ongoing “control” program, outbreaks of the damaging crown-of-thorns starfish – triggered by poor water quality – have spread throughout the reef.
The federal government has recently argued that climate change should not form the basis for an in-danger listing, because rising emissions are not the responsibility of individual countries. The argument comes despite Australia having one of the highest per capita emissions rates in the world.
But as Australia’s greenhouse gas emissions continue to rise – an outcome supported by government policy – the continued downward trajectory of the Great Barrier Reef is inevitable.
If you think climate change is only gradually affecting our natural systems, think again.
Our research, published yesterday in Frontiers in Marine Science, looked at the large-scale impacts of a series of extreme climate events on coastal marine habitats around Australia.
We found more than 45% of the coastline was already affected by extreme weather events caused by climate change. What’s more, these ecosystems are struggling to recover as extreme events are expected to get worse.
There is growing scientific evidence that heatwaves, floods, droughts and cyclones are increasing in frequency and intensity, and that this is caused by climate change.
Corals, seagrass, mangroves and kelp are some of the key habitat-forming species of our coastline, as they all support a host of marine invertebrates, fish, sea turtles and marine mammals.
Our team decided to look at the cumulative impacts of recently reported extreme climate events on marine habitats around Australia. We reviewed the period between 2011 and 2017 and found these events have had devastating impacts on key marine habitats.
These include kelp and mangrove forests, seagrass meadows, and coral reefs, some of which have not yet recovered, and may never do so. These findings paint a bleak picture, underscoring the need for urgent action.
During this period, which spanned both El Niño and La Niña conditions, scientists around Australia reported the following events:
2011: The most extreme marine heatwave ever occurred off the west coast of Australia. Temperatures were as much as 2-4℃ above average for extended periods and there was coral bleaching along more than 1,000km of coast and loss of kelp forest along hundreds of kilometres.
Seagrasses in Shark Bay and along the entire east coast of Queensland were also severely affected by extreme flooding and cyclones. The loss of seagrasses in Queensland may have led to a spike in deaths of turtles and dugongs.
2013: Extensive coral bleaching took place along more than 300km of the Pilbara coast of northwestern Australia.
2016: The most extreme coral bleaching ever recorded on the Great Barrier Reef affected more than 1,000km of the northern Great Barrier Reef. Mangrove forests across northern Australia were killed by a combination of drought, heat and abnormally low sea levels along the coast of the Gulf of Carpentaria across the Northern Territory and into Western Australia.
2017: An unprecedented second consecutive summer of coral bleaching on the Great Barrier Reef affects northern Great Barrier Reef again, as well as parts of the reef further to the south.
Many of the impacted areas are globally significant for their size and biodiversity, and because until now they have been relatively undisturbed by climate change. Some of the areas affected are also World Heritage Areas (Great Barrier Reef, Shark Bay, Ningaloo Coast).
The habitats affected are “foundational”: they provide food and shelter to a huge range of species. Many of the animals affected – such as large fish and turtles – support commercial industries such as tourism and fishing, as well as being culturally important to Australians.
Recovery across these impacted habitats has begun, but it’s likely some areas will never return to their previous condition.
We have used ecosystem models to evaluate the likely long-term outcomes from extreme climate events predicted to become more frequent and more intense.
This work suggests that even in places where recovery starts, the average time for full recovery may be around 15 years. Large slow-growing species such as sharks and dugongs could take even longer, up to 60 years.
But extreme climate events are predicted to occur less than 15 years apart. This will result in a step-by-step decline in the condition of these ecosystems, as it leaves too little time between events for full recovery.
This already appears to be happening with the corals of the Great Barrier Reef.
Damage from extreme climate events occurs on top of more gradual changes driven by increases in average temperature, such as loss of kelp forests on the southeast coasts of Australia due to the spread of sea urchins and tropical grazing fish species.
Ultimately, we need to slow down and stop the heating of our planet due to the release of greenhouse gases. But even with immediate and effective emissions reduction, the planet will remain warmer, and extreme climatic events more prevalent, for decades to come.
Recovery might still be possible, but we need to know more about recovery rates and what factors promote recovery. This information will allow us to give the ecosystems a helping hand through active restoration and rehabilitation efforts.
We will need new ways to help ecosystems function and to deliver the services that we all depend on. This will likely include decreasing (or ideally, stopping) direct human impacts, and actively assisting recovery and restoring damaged ecosystems.
But they will need to be massively scaled up to be effective in the context of the large scale disturbances seen in this decade.
Russ Babcock, Senior Principal Research Scientist, CSIRO; Anthony Richardson, Professor, The University of Queensland; Beth Fulton, CSIRO Research Group Leader Ecosystem Modelling and Risk Assessment, CSIRO; Eva Plaganyi, Senior Principal Research Scientist, CSIRO, and Rodrigo Bustamante, Research Group Leader , CSIRO