Cumulative Stress Impairs Great Barrier Reef Recovery

By Jerri-Lynn Scofield, who has worked as a securities lawyer and a derivatives trader. She is currently writing a book about textile artisans.

Science Advances published a paper this week, Impaired recovery of the Great Barrier Reef under cumulative stress, analyzing the recent decline in corals on the Great Barrier Reef. (The full paper may be found here.)

The paper found that coral recovery declined by 84% between 1992 and 2010, with some key coral types exhibiting close to zero recovery over that time period, while other reefs showed high recovery.

The paper attributed loss in recovery capacity partly to “the cumulative effects of chronic pressures including water quality, warming, and sublethal effects of acute disturbances (cyclones, outbreaks of crown-of-thorns starfish, and coral bleaching.”

Note that the period studied inthis paper 1992-2010– predated the serious back-to-back bleaching events of 2016 and 2017, which killed about half the coral in the 1400 mile long reef, as reported by  Motherboard in The Great Barrier Reef Is Losing Its Ability to Recover from Bleaching Events.

Even with the exclusion of that bleaching, the effects on coral recovery reported are alarming, as Science News notes in Great Barrier Reef not bouncing back as before, but there is hope:

Dr Juan Ortiz, lead author from The Australian Institute of Marine Sciences and UQ’s School of Biological Sciences, said that during this time, average coral recovery rates showed a six-fold decline across the Great Barrier Reef.

“This is the first time a decline in recovery rate of this magnitude has been identified in coral reefs,” he said.

Recovery Possible?

Yet the paper also suggested action could be taken to improve recovery of Great Barrier Reef coral:

Modeled projections indicate that recovery rates can respond rapidly to reductions in acute and chronic stressors, a result that is consistent with fast recovery observed on some reefs in the central and southern GBR since the end of the study period. A combination of local management actions to reduce chronic disturbances and global action to limit the effect of climate change is urgently required to sustain GBR coral cover and diversity.

Improving Water Quality

I encourage anyone with an interest in this topic to read the full paper, which is linked to above.  While news of the deterioration of the Great Barrier Reef  is certainly depressing, what I found most interesting is that the paper’s authors suggested that further decline could be managed by  improving water quality.

The ideal would of course be to reduce or indeed offset climate change, but in the absence of action on that front, water quality improvements alone could also improve coral recovery. From the paper:

The decline in average coral recovery rates is cause for concern, particularly in tabular and digitate corals, which play a disproportionately important role in driving reef dynamics . Moreover, with increasing frequencies and intensities of disturbances, any reduction in recovery rate may facilitate the ratcheting down of average reef state. As identified in our results, climate change is already affecting coral recovery rate both chronically and through the legacy effect of acute thermal events. Our analysis suggests that recovery rates are expected to decline further under climate change and ocean acidification because of impacts on coral recruitment and growth. Thus, we echo many other calls for urgent action to mitigate greenhouse gas emissions and maintain functioning ecosystems. However, while we anticipate that average coral cover will decline, the striking spatial variability in recovery rate implies that some reefs will continue to function far better than others. Understanding the causes of this variability is important and will help target management actions and the delivery of ecosystem services through the identification of reefs/regions, where the ecological benefits of local management action can be maximized. A considerable amount of variance was explained by proxies of water quality. Because water quality can be improved through management and policy, and is the focus of continued government investments, its deleterious influence on coral recovery may weaken in future. The emerging picture is one of substantial heterogeneity that requires carefully tailored management interventions and renewed action on global scales (citations omitted).

Or, to put this into more straightforward English, again over to Science News:

Professor Peter Mumby of the ARC Centre of Excellence for Coral Reef Studies at The University of Queensland, said that this was serious cause for concern, particularly given the accelerating impacts of climate change on reefs, but it is important to stress that not all reefs are failing.

“I believe there is scope for management to help remedy the situation,” he said.

“Our results indicate that coral recovery is sensitive to water quality, and is suppressed for several years following powerful cyclones.

“Some reefs could improve their recovery ability if the quality of the water entering the reef is actively improved.”

This suggestion is not an instance of magical thinking. As Motherboard points out:

Indeed, the Belize Barrier Reef was recently removed from a list of endangered ecosystems through active management and progressive conservation policies implemented by the Belizean government. Similar principles could save the Great Barrier Reef as well, but action must be taken soon.

Now, the paper’s  authors are by no means suggesting that water quality improvements alone will be sufficient to ensure the future health of the Great Barrier Reef:

Dr Ortiz said that the frequency of acute disturbances was predicted to increase, making careful management key.

“The future of the Great Barrier Reef is threatened without further local management to reduce chronic disturbances and support recovery, and strong global action to limit the effect of climate change.”

Scientists not involved with this study also insist on the importance of tackling climate change, as reported by ABC Science in Great Barrier Reef coral recovery slows significantly over 18-year period:

But trying to improve conditions on the reef without tackling climate change is like putting “band-aids on arterial wounds”, according to James Cook University’s Associate Professor Jodie Rummer, who was not involved in the study.

“We definitely need to be controlling problems with water quality and problems with crown of thorns, but first and foremost we need to deal with the big problem,” Dr Rummer said.

“What it does come down to is warming. Everything else just makes it worse, but warming is the primary concern.”

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  1. rd

    I think this article is an example of the challenges facing us moving forward.

    Water quality is largely a local and regional issue focused on a specific watershed for a river, lake, or coastal location. The water quality can be managed and improved through local and regional actions and usually does not require cooperation of widespread national or international entities since the changes are controlled within the watershed. Local and regional (e.g. state) governments have huge influence on whether or not the water quality is improved or degraded further.

    On the other hand, global warming is a cumulative impact from an entire planetful of people and ecologies. So local action can help a tiny bit but it will require millions of local actions in most countries of the world to accumulate to make a significant impact. I am pessimistic that will happen in the near-future, if ever.

    I think much of the research for coral reefs, marine dead zones, etc. has to be focused on differentiating what can be helped by local/regional activities and what is tied to global warming and/or carbon dioxide concentrations (linked, but not the same thing – ocean acidification could occur in the absence of global warming due to CO2 increases in ocean water).

    If local improvements can make a significant difference, then that needs to be dropped squarely on the shoulders of the local/regional governments. Researchers that say local action should be done but then drift off about “but we need to solve global warming…..” just give an excuse to the local entities to do nothing, thereby likely allowing a high percentage of the impacts to remain in place or get worse. Pretty much every major marine dead zone could be largely fixed by cleaning up the watershed activities. Global warming and ocean acidification would likely have impacts but much of that part of the ocean would still be quite functional. Most of our blue-green algae challenges in inland lakes are due to sewage/agriculture practices that can be addressed. Warming contributes to the problem but the algae requires the nutrients to be there to grow and that is addressed through local and regional actions.

  2. Zachary Smith

    This suggestion is not an instance of magical thinking.

    I think I disagree. A focus on the short term things like pollution is unlikely to do more than provide upbeat headlines. The oceans are dying, or to be a bit more precise, being murdered. Given the power structure in Australia, heroic battles against farmers and miners and shipping companies are likely to be losing ones anyhow. But in the slightly longer term none of that will matter anyhow.

    Or, to put this into more straightforward English…

    Good point. I looked at that paper, and concluded it was designed to awe/impress the reader rather than inform him.

  3. The Rev Kev

    I’ll say right now that I am in no way a greenie or an environmentalist. But I will say this. The State of Queensland runs alongside the Great Barrier Reef so primary protection of the Reef is in their own interest as they make a mozza from all the tourists that come visit the Reef. That is why that one may question the idea of BUILDING A FRICKIN’ COAL PORT OPPOSITE THE REEF TO BE RUN BY A MOB WITH THE REPUTATION OF ENVIRONMENTAL VANDALS may not be the brightest idea.

  4. witters

    “In no way an … environmentalist” – yet a critic of “environmental vandalism.” I think this needs sorting out Rev.

    1. The Rev Kev

      It means that I am all for development but only when all external costs have been factored in and I mean ALL external costs. As an example, on paper fracking sounds good but when you factor in all external costs you may find that it would be at the cost of large amounts of methane pumped into the atmosphere as well as losing the underlying water aquifers for farming and for forests for a coupla thousand years so in my books that is a no. Also, if something is sustainable you can do it but if it is not, that is also a big no! e.g fishing, yes. Fishing to the point of total annihilation, uhhh no!

      1. witters

        So, not an environmentalist as the solution to our problems is CBA “with negative (and positive) externalities” counted? OK. Personally I think the logic of capitalism is such that the internalisation of negative externalities is never going to be more than wishful thinking – for under this logic everyone is always rational to try and externalise such externalities…

  5. gordon

    Unlike the RevKev, I could be described as an environmentalist or greenie, I suppose. Perhaps “watermelon” would be the best description of me, though quite often I’m a “reverse watermelon”, with the red on the outside and the green in the middle. Much of the time, however, I display both green and red colouration on the surface – green and red striped, I guess you could say. Or maybe green with big red spots. Or red with big green spots. So now you all know all about me.

    Anyhow, anybody interested in the Great Barrier Reef might like to know that the Australian Federal Govt. has recently thrown just under 1/2 a billion dollars (Australian) at the Reef by means of a donation of taxpayers’ money to an outfit called the Great Barrier Reef Foundation:

    It just looks like an instance of handing taxpayer’s money over to political allies to me. In fact, the real issue is of course regulation, and equally of course neither the Federal nor the Queensland State Govts. are prepared to incur the political odium of doing that. Therefore farmers and miners who pollute the rivers which flow into the sea near the reef will be left unregulated, and in fact probably given money via the Govt. donation to that Foundation.

    The present Queensland Govt. is ALP, so is of course regarded as an enemy by the Federal Govt, which is Liberal/National coalition. There will be no cooperation between them:

    But since the Queensland Govt. is just as averse to regulation as the Federal Govt. is, their cries of outrage ring a bit hollow to me.

    1. The Rev Kev

      Agree with your assessment. And when they Reef finally dies, will they offer the tens of thousands of people out of work then, as there is no Great Barrier Reef to tour any more, “training” to make up for the loss of their jobs? Maybe they can teach them all to be coders.

      1. gordon

        They’ll retrain them all to be Chinese property investors, funded by the Great Barrier Reef Foundation’s successor organisation, the Great Barrier Reef Memorial Foundation (the Board and management unchanged).

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