Extreme weather caused by climate change has damaged 45% of Australia’s coastal habitat



Bleached staghorn coral on the Great Barrier Reef. Many species are dependent on corals for food and shelter.
Damian Thomson, Author provided

Russ Babcock, CSIRO; Anthony Richardson, The University of Queensland; Beth Fulton, CSIRO; Eva Plaganyi, CSIRO, and Rodrigo Bustamante, CSIRO

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.




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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.

Life on the coastline

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.

Healthy kelp (left) in Western Australia is an important part of the food chain but it is vulnerable to even small changes in temperature and particularly slow to recover from disturbances such as the marine heatwave of 2011. Even small patches or gaps (right) where kelp has died can take many years to recover.
Russ Babcock, Author provided

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.

Heritage areas affected

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).

Seagrass meadows in Shark Bay are among the world’s most lush and extensive and help lock large amounts of carbon into sediments. The left image shows healthy seagrass but the right image shows damage from extreme climate events in 2011.
Mat Vanderklift, Author provided

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.

Gradual decline as things get warmer

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.




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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.

Several such programs are active around Australia and internationally, attempting to boost the ability of corals, seagrass, mangroves and kelp to recover.

But they will need to be massively scaled up to be effective in the context of the large scale disturbances seen in this decade.The Conversation

Mangroves at the Flinders River near Karumba in the Gulf of Carpentaria. The healthy mangrove forest (left) is near the river while the dead mangroves (right) are at higher levels where they were much more stressed by conditions in 2016. Some small surviving mangroves are seen beginning to recover by 2017.
Robert Kenyon, Author provided

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

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Great Barrier Reef Rescue?


‘Sadness, disgust, anger’: fear for the Great Barrier Reef made climate change feel urgent



Tourists are experiencing ‘Reef grief’.
Matt Curnock, Author provided

Matt Curnock, CSIRO and Scott Heron, James Cook University

Media coverage of mass coral bleaching on the Great Barrier Reef may have been a major tipping point for public concerns around climate change, according to research published today.

Severe and extensive bleaching during the summers of 2016 and 2017 has been directly attributed to human-caused climate change. Much of the ensuing media coverage used emotional language, with many reports of the Reef dying.




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While the physical effects of the bleaching have been well documented, we wanted to understand the social and cultural impact.

Our research, including a study published today in Nature Climate Change, has compared survey responses from thousands of Australians and international visitors, before and after the bleaching event.

Reef grief

Our research team conducted face-to-face interviews with 4,681 visitors to the Great Barrier Reef region, in 14 coastal towns from Cooktown to Bundaberg, over June to August in both 2013 and 2017. We asked more than 50 questions about their perceptions and values of the Reef, as well as their attitudes towards climate change.

We found a large proportion of respondents, including Australians and overseas visitors, expressed forms of grief in response to loss and damage to the iconic ecosystem. Negative emotions associated with words given in short statements about “what the Great Barrier Reef means to you”, included sadness, disgust, anger and fear.




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Emotional appeals are widely used in media stories and in social media campaigns, and appealing to fear in particular can heighten a story’s impact and spread online.

However, a side-effect of this approach is the erosion of people’s perceived ability to take effective action. This is called a person’s “self-efficacy”.
This effect is now well documented in reactions to representations of climate change, and is actually a barrier to positive community engagement and action on the issue.

In short, the more afraid someone is for the Great Barrier Reef, the less they may feel their individual efforts will help to protect it.

While our results show a decline in respondents’ self-efficacy, there was a corresponding increase in how highly they valued the Reef’s biodiversity, its scientific heritage and its status as an international icon. They were also more willing to support action to protect the Reef. This shows widespread empathy for the imperilled icon, and suggests greater support for collective actions to mitigate threats to the Reef.

Researchers surveyed thousands of visitors to the Great Barrier Reef in 2013 and 2017.
Matt Curnock, Author provided

Changing attitudes

We observed a significant increase in the proportion of people who believe that climate change is “an immediate threat requiring action”. In 2013 some 50% of Australian visitors to the Great Barrier Reef region agreed climate change is an immediate threat; in 2017 that rose to 67%. Among international visitors, this proportion was even higher (64% in 2013, rising to 78% in 2017).

This represents a remarkable change in public attitudes towards climate change over a relatively short period. Previous surveys of Australian climate change attitudes over 2010 to 2014 showed that aggregate levels of opinion remained stable over that time.

Comparing our findings with other recent research describing the extent of coverage and style of reporting associated with the 2016-2017 mass coral bleaching event, we infer that this event, and the associated media representations, contributed significantly to the shift in public attitudes towards climate change.

Moving beyond fear

As a source of national pride and with World Heritage status, the Great Barrier Reef will continue to be a high profile icon representing the broader climate change threat.

Media reports and advocacy campaigns that emphasise fear, loss and destruction can get attention from large audiences who may take the message of climate change on board.

But this does not necessarily translate into positive action. A more purposeful approach to public communication and engagement is needed to encourage collective activity that will help to mitigate climate change and reduce other serious threats facing the Reef.

Examples of efforts that are underway to reduce pressures on the Reef include improvements to water quality, control of crown-of-thorns starfish outbreaks, and reducing poaching in protected zones. Tourism operators on the Reef are also playing an important role in restoring affected areas, and are educating visitors about threats, to improve Reef stewardship.

Clearly there remains an immediate need to reduce greenhouse gas emissions to ensure the Reef’s World Heritage qualities are maintained for future generations.

However, maintaining hope, and offering accessible actions towards attainable goals is critical to engaging people in collective efforts, to help build a more sustainable future in which coral reefs can survive.


The authors would like to acknowledge Nadine Marshall, who co-wrote this article while employed by CSIRO. We thank our other co-authors of the Nature Climate Change paper, including Lauric Thiault (National Center for Scientific Research, PSL Université Paris), Jessica Hoey and Genevieve Williams (Great Barrier Reef Marine Park Authority), Bruce Taylor and Petina Pert (CSIRO Land and Water) and Jeremy Goldberg (CSIRO & James Cook University). The scientific results and conclusions, as well as any views or opinions expressed herein, are those of the authors and do not necessarily reflect those of the Australian Government or the Minister for the Environment, or the Queensland Government, or indicate commitment to any particular course of action.The Conversation

Matt Curnock, Social Scientist, CSIRO and Scott Heron, Senior Lecturer, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Coral reproduction on the Great Barrier Reef falls 89% after repeated bleaching


Morgan Pratchett, James Cook University

The severe and repeated bleaching of the Great Barrier Reef has not only damaged corals, it has reduced the reef’s ability to recover.

Our research, published today in Nature, found far fewer baby corals are being produced than are needed to replace the large number of adult corals that have died. The rate at which baby corals are settling on the Great Barrier Reef has fallen by nearly 90% since 2016.

While coral does not always die after bleaching, repeated bleaching has killed large numbers of coral. This new research has negative implications for the Reef’s capacity to recover from high ocean temperatures.

How coral recovers

Most corals reproduce by “spawning”: releasing thousands of tight, buoyant bundles with remarkable synchronisation. The bundles burst when they hit the ocean surface, releasing eggs and/or sperm. Fertilised eggs develop into larvae as they are moved about by ocean currents. The larvae settle in new places, forming entirely new coral colonies. This coral “recruitment” is essential to reef recovery.




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The research team, led by my colleague Terry Hughes from the ARC Centre of Excellence for Coral Reef Studies, measured rates of coral recruitment by attaching small clay tiles to the reef just before the predicted mass spawning each year. These settlement panels represent a standardised habitat that allows for improved detection of the coral recruits, which are just 1-2mm in size.

Almost 1,000 tiles were deployed across 17 widely separated reefs after the recent mass bleaching, in late 2016 and 2017. After eight weeks they were collected and carefully inspected under a microscope to count the number of newly settled coral recruits. Resulting estimates of coral recruitment were compared to recruitment rates recorded over two decades prior to the recent bleaching.

Australian Academy of Science.

Rates of coral recruitment recorded in the aftermath of the recent coral bleaching were just 11% of levels recorded during the preceding decades. Whereas there were more than 40 coral recruits per tile before the bleaching, there was an average of just five coral recruits per tile in the past couple of years.




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Reef resilience

The Great Barrier Reef (GBR) is the world’s largest reef system. The large overall size and high number of distinct reefs provides a buffer against most major disturbances. Even if large tracts of the GBR are disturbed, there is a good chance at least some areas will have healthy stocks of adult corals, representing a source of new larvae to enable replenishment and recovery.

Larvae produced by spawning corals on one reef may settle on other nearby reefs to effectively replace corals lost to localised disturbances.

It is reassuring there is at least some new coral recruitment in the aftermath of severe bleaching and mass mortality of adult corals on the GBR. However, the substantial and widespread reduction of regrowth indicates the magnitude of the disturbance caused by recent heatwaves.

Declines in rates of coral recruitment were greatest in the northern parts of the GBR. This is where bleaching was most pronounced in 2016 and 2017, and there was the greatest loss of adult corals. There were much more moderate declines in coral recruitment in the southern GBR, reflecting generally higher abundance of adults corals in these areas. However, prevailing southerly currents (and the large distances involved) make it very unlikely coral larvae from southern parts of the Reef will drift naturally to the hardest-hit northern areas.

It is hard to say how long it will take for coral assemblages to recover from the recent mass bleaching. What is certain is low levels of coral recruitment will constrain coral recovery and greatly increase the recovery time. Any further large-scale developments with also greatly reduce coral cover and impede recovery.




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Reducing carbon emissions

This study further highlights the vulnerability of coral reefs to sustained and ongoing global warming. Not only do adult corals bleach and die when exposed to elevated temperatures, this prevents new coral recruitment and undermines ecosystem resilience.

The only way to effectively redress global warming is to immediately and substantially reduce global carbon emissions. This requires that all countries, including Australia, renew and strengthen their commitments to the Paris Agreement on climate change.

While further management is required to minimise more direct human pressure on coral reefs – such as sediment run-off and pollution – all these efforts will be futile if we do not address global climate change.The Conversation

Morgan Pratchett, Professor, ARC Centre of Excellence for Coral Reef Studies, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.