Example of ‘Unknown Unknowns,’ Study Detailing ‘Almost Instant Mortality of Corals’ Suggests Crisis Worse Than Previously Understood

Jerri-Lynn here. Not much I can add to this grim and depressing report other than a link to the full study, Rapid Coral Decay Is Associated with Marine Heatwave Mortality Events on Reefs, for readers who might like to take a deeper dive into details.

By Jessica Corbett, staff writer at Common Dreams. Originally published at Common Dreams

As the human-caused climate crisis drives up ocean temperatures at a rate that has scientists worried, a study published Thursday in the journal Current Biology reveals that warming waters are an even bigger threat to coral reefs than experts previously realized.

Past research has raised alarm about how ocean pollution and rising temperatures cause coral bleaching—which is when coral expels algae, its main food source, and turns white. Although more susceptible to disease and death, bleached coral can recover if temperatures fall, so some scientists have been hopeful that urgent climate action could revive impacted reefs.

However, the new study—conducted by researchers at the University of New South Wales Sydney, the University of Newcastle, the University of Technology Sydney, James Cook University, and the National Oceanographic and Atmospheric Administration (NOAA)—heightens concerns about the future of coral reefs in a warming world.

According to the study:

Severe marine heatwaves have recently become a common feature of global ocean conditions due to a rapidly changing climate. These increasingly severe thermal conditions are causing an unprecedented increase in the frequency and severity of mortality events in marine ecosystems, including on coral reefs… [M]arine heatwave events on coral reefs are biologically distinct to how coral bleaching has been understood to date.

“Until now, we have described coral bleaching as an event where the symbiotic relationship between coral and its microbes breaks down and corals lose their main source of nutrition, and the coral can die if the symbiosis is not restored,” co-author Tracy Ainsworth, an associate professor at Australia’s University of New South Wales Sydney, explained in a statement.

“But what we are now seeing is that severe marine heatwave events can have a far more severe impact than coral bleaching,” Ainsworth continued. “The water temperatures are so warm that the coral animal doesn’t bleach—in terms of a loss of its symbiosis—the animal dies and its underlying skeleton is all that remains.”

“We find that the skeleton is immediately overgrown by rapid growth of algae and bacteria,” said co-author Bill Leggat, an associate professor at the U.K.’s University of Newcastle. By CT scanning the coral skeleton, Leggat said, the team found that “this process is devastating not just for the animal tissue, but also for the skeleton that is left behind, which is rapidly eroded and weakened.”

Laura Richardson at the U.K.-based Bangor University’s School of Ocean Sciences – who was not involved in the study – told BBC News that the team’s significant discovery was “the rapidity with which the reef skeleton breaks down when you have these severe heatwaves.”

They are the first researchers, as Richardson noted, to document that such events are causing “almost instant mortality of corals.”

“Climate scientists talk about ‘unknown unknowns’ – impacts that we haven’t anticipated from existing knowledge and experience,” said study co-author Scott Heron of Australia’s James Cook University. “This discovery fits into this category.”

“As we begin now to understand this impact,” Heron added, “the question is how many more of these ‘unknown unknowns’ might there still be that could bring faster and greater damage to coral reefs from climate change.”

Though the study generated alarm, the researchers expressed hope that it will spur public outcry for policymakers to pursue bolder efforts to combat the climate crisis—and, specifically, protect coral reefs, particularly considering the anticipated consequences of inaction.

PBS News Hour reported that “without the option to recover, the world may start seeing corals die off faster than expected. And the death of corals would come with a steep cost for humans: flood protection that’s worth tens of millions in the U.S. alone, plus an estimated value of almost $30 billion each year globally in tourism, fishing, and other benefits.”

“Across the globe coral reefs are still a source of inspiration and awe of the natural world, as well as being critically important to the communities that rely upon them,” said Ainsworth. “Given that the degradation of coral reefs will result in the collapse of ecosystem services that sustain over half a billion people, we urgently need actions both globally and locally that protect and conserve these truly wonderful places.”

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  1. Ignacio

    We are navigating through uncharted territory and pretending there are now risks. The captain is drunk, the pilot sleeping, the crew on strike and the passengers dancing. Everything is under control.

  2. PlutoniumKun

    This is something that has always deeply worried me about climate science. There is a well recognised form of epistemological error that arises from reductionist thinking that breaking down problems into variables that can be studied results in excessive confidence in the result – the problem comes from the variables overlooked or ignored. Or put another way, forgetting about the ‘unknown unknowns’. All scientists should be well aware of this, but I see it all the time in papers – comments like ‘we have assessed all the animal studies and none have revealed excess cancer rates, therefore the product is considered safe’. This is why the precautionary principle was invented, and why it is so very important.

    Climate science is so complex it is absolutely inevitable that there will be overlooked variables. Of course, these variables could impact either positively or negatively, but for all sorts of reasons the likelihood of them being negative (i.e. positive feedbacks or unpleasant surprises) is higher. So it was always very likely that, even allowing for political pressures, mainstream science would err on the side of understating risk. This is one reason among others why so many economic studies based on the science are junk, they are assuming a far greater degree of predictability than is possible.

    Another further issue is that global models are very poor at predicting localised impacts. I’ve sat in talks from engineers solemnly discussing how they have built predicted climate change impacts into (for example) flood mitigation designs. But talk to the modellers and they’ll tell you it is simply impossible to extrapolate their predictions down to the scale of an individual flood basin. The engineers are basing their designs on what amounts to guesswork, disguised as sound science.

    The reality is that we will be hit with more and more of these bad news stories, many completely coming from left field. This is the world we’ve built.

    1. Ignacio

      Following your thinking I think that the next step for us, the common people, is to realise that not only there may be coming many negative surprises but also there is not a private or public service/agency that we can rely in case a nasty surprise comes to our neighbourhood. We should think twice when making decisions and consider vulnerabilities associated with them. For instance. Will I enjoy unlimited access to natural gas in the following 20 years to heat my house? Not sure. Will my government provide a solution in case supply is interrupted? Unlikely. Will be more reliable a heating system based on electricity? May be. Should then I change my heating system and can I afford it? Yes and no. What is then my priority? Will i suffer hotter summers because of climate change or colder winters beacuse the gulf stream weakens? May be both.

      Even though I am aware of some of the risks and despite my knowledge on heating, cooling and ventilation systems is well above the average it is not easy for me to make decisions in this sense. I just can try to avoid making big mistakes, but most people has to rely on others counselling. Not surprisingly we keep making big mistaken decisions.

      1. PlutoniumKun

        Indeed – as systems become more complicated and interlinked, we are losing the ability to be self-reliant. I’m old enough to remember when most people repaired their own cars and their heating/electrical systems. This simply isn’t possible anymore.

        Maybe more decentralised systems and the growth in home batteries, etc., will increase resilience, but I’m becoming less sure of this.

        Sometimes I think those crazy preppers living in the wilds of Montana were actually right all along.

        1. oaf

          …Crazy like foxes!…Government will provide *solutions* for elites first, and foremost…the rest of us?…we are counted on to *take care of* (euphemism) each other….

        2. Jeremy Grimm

          Resilience and self-reliance is not a personal matter alone. It is also a concern for local communities, and for nations. It is one thing to repair your own car, HVAC, or … but where does the replacement part come from?

      2. Bobby Gladd

        We moved to Baltimore four months ago. There were some attractive houses in our price range close to the bay / marina areas. We thought “all it wold take would be one hurricane storm surge and we could be literally underwater.”

        We bought instead in the Homeland District in the city, north of downtown (close to Hopkins). Elevation 400 ft above sea level.

        Last week, downtown BMore and the adjacent Fells Point restaurant and entertainment district had 12-18″ of water in the streets in the wake of an intense, soggy storm.

        Stuff is coming.

        1. Ignacio

          Good example of the kind of reasoning we now have to do. Then, once one finds a relatively safe place you have to go to the details. Is the orientation adequate? Is the house properly buildt according to the climate or does it need refurbishing? Are HVAC systems appropriate or easily replaceable? Do I have space for PV pannels without shadowing? Do I really need a guest room…

    2. john buell

      Could you explain briefly why the feedback loops tend to be positive, ie generally destructive.

      1. rd

        It comes from electrical engineering. Feedback is when a wave is fed back into itself, like a microphone in front of a speaker. That ear splitting sudden screech is the “positive” feedback as the amplitude rapidly spikes as it feeds back onto itself.

        “Dampening” is where the wave amplitudes get smaller, usually because an opposite wave is being fed in that dampens the first, similar to a shock absorber in a car. The oceans have likely been dampening the impacts of climate change and CO2 because they are huge and absorb a lot of heat and CO2. At certain points, the ability to absorb can decline or disappear and then “breakthrough” happens where the full effects can be felt. This is what happens with chemical filtering systems where it absorbs the contaminant until the absorption capacity is used up and then it simply flows through. This is why filters in the fridge or water system need to be replaced periodically.

      2. Elspeth

        Positive feedback in science is generally means that energy produced by a system is returned back to that system. In general the underlying system can not handle the energy and maintain equilibrium.

      3. Jeremy Grimm

        I must apologize. I did not read where PlutoniumKun stated “for all sorts of reasons the likelihood of them being negative (i.e. positive feedbacks or unpleasant surprises) is higher.”

        I believe he is indicating — we once enjoyed an Earth with a relatively stable climate system operating around conditions pleasant for our species. Humankind has wrecked a tremendous increase in the amount of CO2 in our atmosphere and done so over a remarkably short period of roughly one century. Responding to this input, the Earth’s climate system is shifting out of the stable comfortable climate conditions we once enjoyed.

        Feedback loops do not tend to be positive or negative. By convention in systems design, electronics, and modeling, feedbacks that work as ‘corrective’, controlling, feedbacks, working to maintain system stability are labeled negative, and feedbacks having the opposite effect are labeled positive feedbacks. If you accept that we are moving away from our relatively stable, well-behaved climate — which is unpleasant to say the least — the likelihood of positive feedback loops would indeed tend to be higher. [It might be more accurate to assert that the positive feedbacks to the system tend to swamp the negative feedbacks as the climate moves away from its stable state. If your comment were intended to question whether the climate is becoming more unstable you should look into buying a nice beachfront property in Florida or Delaware.]

        Climate systems are nonlinear. There may be unknown variables as yet unaccounted for in climate models. I think this might be restated to say existing models are incomplete and probably do not model some effects we will soon see as the Earth’s climate system moves toward new conditions. Studies of paleoclimate suggest we should expect many effects not predicted by existing models but indicated in the record of Earth’s past climates. It should be no surprise that existing models poorly model climate at smaller scales.

        1. Yves Smith

          I know what you are trying to convey, but your statement is inaccurate: “Feedback loops do not tend to be positive or negative.”

          A feedback loop most decidedly DOES have a tendency, and the way the term is used colloquially is typically the reverse of the actual meaning.

          A postive feedback loop is self-amplifying. Those are destabilizing.

          A negative feedback loop is self-dissipating. From the Oxford Dictionary:

          negative feedback

          noun: Biology

          the diminution or counteraction of an effect by its own influence on the process giving rise to it, as when a high level of a particular hormone in the blood may inhibit further secretion of that hormone, or where the result of a certain action may inhibit further performance of that action.
          the return of part of an output signal to the input, which is out of phase with it, so that amplifier gain is reduced and the output is improved.

          1. Ian Perkins

            While any one feedback loop is either negative or positive, I think john buell (comments, above) has a valid and interesting question (in response to PlutoniumKun): why do climate feedback loops tend to be positive, if indeed they do?
            The comments above don’t seem to answer that, in my view.
            There are some (potential) negative feedbacks – for example, more CO2 (potentially) means faster growth of vegetation, which draws down more CO2.
            If we are to believe the recent surge in papers warning of accelerating climate change – and I do – the positive feedback is overwhelming any negative feedback, but I see no a priori reason for supposing this would be the case. (As an aside, the Gaia hypothesis would hold that the negative feedbacks would dominate, ie. the system – which includes us – would tend to remain stable.)

            1. Jeremy Grimm

              If you agree that the climate is moving away from a stable state — hopefully to a new stable state — then “the positive feedback is overwhelming any negative feedback.” It is a tautology.

              Why is the climate moving away from a stable state? Answer: We added a tremendous amount of CO2 to the atmosphere in an extremely short period of time such that it might not be unreasonable to call the increase in CO2 a step input. If negative feedbacks for the impacts of CO2 dominated the climate system, the climate would tend to settle back to stable state. Eventually negative feedbacks will again dominate the system and we will reach a relatively stable climate state — as I recall — probably a climate similar to the climate during the Holocene.

    3. Jeremy Grimm

      Your comment might be interpreted as impugning climate science and science in general, but I doubt this is intended. Climate scientists are not the ones who asked for a carbon budget for meeting temperature rise ‘X’. Scientists didn’t work to eliminate basic research in favor of research ‘contracts’. The lab workers [scientists?] testing chemicals for potential cancer impacts are following a protocol designed under the rubric of science for other than scientific purposes. The civil engineers building to the specifications of the ‘predicted’ impacts of future flooding know full well they are building to WAGS — but they are ‘certified’ WAGS that fit budgets, deadlines, protect profit margins, and cover asses.

      1. Ignacio

        Jeremy, I don’t think the commentary was intended to impugnate climate science but to underline its limitations regarding the anticipation of future climate change-associated events. One shouldn’t feel comfortable with IPCC predictions even if they are backed by the best science we can produce.

        1. Jeremy Grimm

          The thrust of my comment above was to suggest the statements of our Science are subject to the constraints of disciplines other than Science, disciplines such as Neoliberal Markets. I have never been less than skeptical of the IPCC predictions. Most of the IPCC predictions tend to assume relatively moderate quasi-linear behavior. We are already observing chaotic weather and other indications the climate transition we will experience will not be moderate, nicely behaved, or gentle. Instead of nice relatively linear changes I suspect we will experience transitions better fit with exponential curves.

          Climate systems are complex nonlinear systems with many as yet unobserved and unknown behaviors. In modeling such systems the best approach is the approach PlutoniumKun described as “reductionist thinking that [of] breaking down problems into variables that can be studied.” As he states this approach has limitations, but I believe it is the best approach that can be made for modeling such a complex system as the climate. The “excessive confidence in the result” may be attributed to an “epistemological error” but I believe most scientists and perhaps most engineers are well aware of that error and study avoiding it. It is ingrained in these disciplines. That is to say — climate scientists are not the ones who asked for a carbon budget for meeting temperature rise ‘X’.

  3. Festoonic

    My new favorite quote:
    “If climate change becomes The Big Unstoppable spreading its brimming flush over us with mesmerizing vastness, then we can do no more than fall silent in awe of it as we are of the starry night sky above: too immense—too enigmatic for us to comprehend, but looking up into that dark dome, as we try to thrive amid the neoPermian dilemma and ruins of our own doing, it is worth remembering that the arc of life is filled with marvelous and wondrously imaginative vitality to continue on in slight, slow, steady strides with no assurance we will be among the resurrected.” http://www.artfarmnebraska.org/

    1. Eclair

      Thank you for the link, Festoonic. I rather like this quote, from the same source:

      Our notion of nature, like life and love, is something we pretend we know the true ways of, but we live satisfied with the piles of lies we build around it, offered as shape and structure for metaphors we expound. If we ignore the western tradition that presumes nature as separate and open to all projects, a precept intimately handled with onanistic exuberance by real estate speculators and developers, then perhaps there is a possibility for integrating the referent, ‘self’ and the environment. Nature has not always approved of our meddling nor have we always been equal to or qualified through fragile judgment to meet the tasks envisioned, but there is no need for forever foreclosing any effort due to past examples of blank incompetence. An alternative to approaching nature in a no-knock police raid manner, or treating it like a backseat queen, might be to mingle with it by measured invitation, subsidized by other minds previously there living in accord with it. Think of nature as an aesthetic lay-a-way program, waiting for us to collect the ecstasy of an exhilarating moment surrounding us in a special domain. We could go on pretending, remaining indifferent to this caucus—shouldn’t be difficult…

      1. TheCatSaid

        Or one could learn to communicate directly with nature and learn how to move towards balance in any particular situation. I’m talking two-way communication regardless of the “sensitivity” of one’s personal sensory system. See any of the books by Machaelle Small Wright who shares information generously so that others do not have to reinvent the wheel and can get practical info quickly.

        Disregard this suggestion if you believe that nature does not have information that would be useful, or if you believe that nature is not capable of communication.

        1. Eclair

          Well, you are talking to someone who converses with plants and murmurs to the bees and other pollinators in the garden when wading in to pull weeds (wait! what are weeds?). And who has finally realized, after watching several raspberry plants die in a certain location, that the vigorous ‘volunteers’ 500 yards away around a pile of stacked boards (been there for decades) was telling me something. So I checked out Wright’s books. Interesting.

          Although I resist the temptation to become lost in contemplation of the awe of nature and the inevitability of climate devastation. Humans caused it and humans have the power to mitigate it.

          1. TheCatSaid

            IMO and personal experience it is useful to ask nature how to remedy a situation, compared to me trying to figure it out from a well-intentioned human standpoint. Humans working in a conscious equal partnership is an awesome combination. Humans trying to figure it out on their own–I’m not sure we have enough room for error, seeing our track record so far.

            1. TheCatSaid

              I meant to say, “humans working in a conscious equal partnership with nature is an awesome combination.

              It’s that partnership that’s unbelievably powerful.

          2. False Solace

            > Humans caused it and humans have the power to mitigate it.

            No doubt a comforting belief, but it’s usually much easier to break a thing than to rebuild or repair it.

  4. ChristopherJ

    The precarious state of the oceans, the ultimate commons, which all countries seem to mess up as it all seems like just a drop…

    Over here near the Barrier Reef, most thinking people have assumed it will be gone soon, bleached away by the overly warmer waters we now see in this part of the world. We’ll scramble along for a while as we, currently, have a rain forest which the punters seem to like, but the place won’t be the same when the oceans animals have all gone.

    Our government, in its inexorable pursuit of climate change, wherever it occurs, granted around $450m or so to some unknown company headed by insiders, to, well, save the reef.

    It’s a lot of money and its giving without tender caused some temporary embarrassment, all forgotten now and our politicians are without any modicum of shame. But it won’t be enough. Way too late for that.

    Still, the idea to erect some shade cloth to keep the reef waters cooler seems to have some traction and will keep the sail makers in coin for the while. I’m sure the pilot work they’ve been doing down at the local swimming pool will scale

    1. Samuel Conner

      The thought occurs that the reefs would be a great place to experiment with the concept of “marine cloud brightening”. Local experiments could produce limited area cooling while working out the bugs in the method.

      I don’t know whether it is known that this is a useful method at global scale, but perhaps is worth development effort in a precautionary “all of the above” sense. And even if it turns out to not be useful at global scale, the experiments may help to save some of the small area ecosystems.

  5. rd

    Coral reefs frequently undergo major stresses: https://www.sciencemag.org/news/2018/05/great-barrier-reef-has-had-five-near-death-experiences-past-30000-years

    They are quite adaptable over time. The big thing is if we keep piling on multiple major stressors, such as sea level rise, nutrients from pollution, sediment from increased erosion etc., that is when the really big damage is likely to occur. The coral reefs may have to reform over time in different places but the short-term impacts on sea life would be very large.

    1. TheCatSaid

      I read a study about a year ago. The author looked at coral reef growth more comprehensively that other studies, and found surprisingly little change. The surprise was that coral reefs in many places actually showed growth, while others nearby showed serious decline. The big correlation with the reefs showing decline was the extent of “development”, especially pollution and sewage caused by human activities. I wish I could find the link because it was thought-provoking.

      1. rd

        Bottom trawling with nets for fishing is also very damaging. Here is a list of damaging things from NOAA: https://oceanservice.noaa.gov/education/kits/corals/coral09_humanthreats.html

        One of my big issues with the hyper focus on greenhouse gases and climate change is that it is positioned as an “all or nothing” problem. In reality, many of the problems attributed to climate change are greatly exacerbated by other anthropogenic problems. If we didn’t have the other stressors in the system, the climate change problem causing great damage might still be barely perceptible.

        Tropical Storm Harvey in Houston was an example – yes, the storm was really bad with lots of rain but the area had positioned itself so badly for such a storm that the development was a massive multiplier of the effects. The ground’s ability to absorb and detail rainwater had essentially been destroyed while lots of things were put in the direct path of flooding and floodways.

        The dead zone at the mouth of the Mississippi is another example along with most toxic blue-green algae blooms.

        1. Boatwright

          Seldom discussed is the affect of toxic agri-chemicals. Millions of pounds of herbicides that are known to be toxic to coral algae are spread on cropland, lawns and golf courses all over the world.

          We seem to imagine that these poisons magically disappear when they flow into the oceans. I have personally witnessed coral die offs immediately after new golf courses have been built at coastal resorts. Formerly healthy reef systems turn into dead zones within a year or two. I saw this happen 20 or 30 years ago — long before the recent spikes in ocean temperatures.

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