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Shifting Baselines and Dying Oceans

by Donald Prothero, Dec 19 2012

These tiny planktonic snails known as pteropods, or “sea butterflies”, are critically sensitive to small changes in ocean acidity, and are now vanishing as the oceans dissolve their thin shells. Without their huge numbers in the plankton, many animals higher up the food chain will die, too.

As we approach the phony hysteria over the end of the world this coming Friday, it’s worthwhile to consider some real threats to the planet. Climate deniers try to distort or obfuscate the evidence about the changing atmosphere, and it’s not always easy to give overwhelmingly conclusive data that would convince them.  In some cases the data are tricky to analyze, or do not have well-documented long-term histories necessary to answer every concern about whether recent weather events are truly unprecedented. The atmospheric system is very complicated, with many different processes operating on short-term, medium-term, and long-term time scales, and not all of it is as well understood as we would like. Thus, the arguments over changes in earth’s atmosphere often reach an impasse.

Not so for the oceans. Although oceans are an even larger system than the atmosphere, we understand them much better. More importantly, we have an excellent long-term record of how the oceans have changed over millions of years from thousands of deep-sea cores, and from the paleontological record of marine fossils that goes back over 700 million years. And unlike the atmospheres, oceans change very slowly over time, since the thermal inertia of water makes the seas very resistant to change except on long-term time scales. In addition, most ocean currents move slowly compared to atmospheric currents. So no matter what you want to make of the data showing atmospheric change, the changes in the oceans are more alarming, since oceans require immense stimuli to cause such change.

A few years ago, marine biologist and film-maker Randy Olson (famous for his film “Flock of Dodos“, which lampoons not only creationists but also arrogant scientists who refuse to communicate with the public) founded a web-based effort to publicize the destruction of the oceans. Named “Shifting Baselines,” it refers to the fact that many ecological systems have shifted to a “new norm” or “new baseline,” and conditions no longer return to those they exhibited only 30 years ago. For example, long-term divers and marine biologists have all documented dramatic changes in the oceans, especially coral reefs. When Olson and most senior marine biologists began diving, coral reefs were thriving around the world, and these same people are now documenting the rapid deterioration of reefs around the world in a single lifetime. Thus, the “baseline” of what is considered normal marine diversity has changed in just a few decades, and biologists being trained today have a very different concept of “normal” marine diversity than those just 30 years ago. As my friend and colleague Jeremy Jackson of the Smithsonian put it, “Every ecosystem I studied is unrecognizably different from when I started. I have a son who is 30, and I used to take him snorkeling on the reefs in Jamaica to show him all the beautiful corals there. I have a daughter who is 17—I can’t show her anything but heaps of seaweed.” Or as marine biologist Steve Miller of the University of North Carolina, Wilmington, wrote:

“Caribbean coral reefs of the 1970s changed my life. But the reefs I first knew and loved are gone, casualties of disease, coral bleaching, and overfishing. The reefs I study now in Florida are only a shadow of their former glory. My tourist friends go snorkeling and marvel at the colors and structure, but little do they know they’re looking at the ghost of a coral reef. While I can tell my friends about all that we have lost, I am saddened that my children can’t have the same personal experience I had, just 25 years ago.”

Although overfishing and disease are certainly important problems in the oceans, the biggest problem seems to be that the oceans are becoming warmer and more acidic as they absorb the excess heat and carbon dioxide from the atmosphere and turn it into carbonic acid. For a long time, some people argued that we didn’t need to worry about carbon dioxide, because the oceans would serve as a big buffer and absorb it all. Well, if that were ever true, it is no longer. The evidence is overwhelming that the acidity of the ocean is changing faster than it has in 300 million years. This, more than any other factor, is responsible for the world-wide dying of the tropical coral reefs. Known as “bleaching,” it occurs when the individual coral polyps (which look like tiny sea anemones) cannot tolerate the environmental conditions, such as excess heat or acid ocean waters, any longer. They shed their symbiotic algae (zooxanthellae), which in normal times help them metabolize carbon dioxide and build their skeletons, and thus lose their color. Eventually, the coral polyps die off, leaving their huge stony skeletons behind which gradually turn white. Although some reefs, like the Great Barrier Reef of Australia, are also suffering from problems like out-of-control predation by the crown-of-thorns sea star, the worldwide bleaching and dying of coral reefs can only be attributed to a global oceanographic change—and only ocean warming and acidification fits that description. Certainly, there are certain marine organismsthat thrive in warmer, more acidic oceans (such as the algae that cause the deadly red tide, or encrusting algae growing on rocks uncropped, plus sand fleas, some less calcified crustaceans, and sea urchins), but the vast majority of marine species are negatively affected. Once the reef corals themselves die, nearly all the hugely diverse community of animals and plants vanishes soon thereafter, leaving a mass of dead stony coral rock covered by algae where once a gloriously beautiful and diverse reef community lived.

Huge areas of the world’s coral reefs are now bleached white and dead.

If the loss of the coral reefs and their huge effect on diversity were not worrisome enough, there is even more direct evidence of what ocean acidification is doing to the marine realm. Several studies have just reported new data that shows the shells of sea creatures are now dissolving faster than they can be grown. First spotted in the thin-shelled planktonic mollusks known as pteropods (or “sea butterflies”) in the Antarctic waters (where colder water allows higher carbon dioxide concentrations), this is an alarming sign. Once the rest of the world’s oceans become acidic enough, most calcareous shelled invertebrates (especially the world’s population of clams and snails, plus echinoderms, some sponges, and corals) will literally dissolve away as larvae before their shells can grow. In addition, the loss of the planktonic pteropods (and most other calcareous plankton, such as foraminifera and coccolithophorid algae) will wipe out the marine plankton that are the base of the food chain throughout the world’s oceans. Once the plankton vanish, so do their predators higher up, leading eventually to most of the world’s fish and whales, all of which feed on smaller animals from lower in the food chain. This would cause a dramatic extinction in the world’s oceans. It would have adverse effects not only on our need for seafood to help provide protein for some of the 7 billion people on the planet, but dead oceans have a huge effect on the atmosphere as well. Once the calcareous planktonic algae vanish, they remove our largest absorber of carbon dioxide from the atmosphere, since the world’s planktonic algae have a much bigger effect on atmospheric carbon dioxide than do the land plants in rainforests and elsewhere (which are also diminishing due to deforestation).

Even more alarming is how quickly this is all happening. In one lifetime, marine biologists have witnessed widespread mass extinction in the coral reef community, and the first signs of oceans so acidic that the marine shelled organisms are dissolving before our eyes. As studies have shown, this is faster than at any time in geologic history, even the famous “methane burp” event 55 million years ago which caused a sudden spike in carbon dioxide and worldwide mass extinction in the ocean.

As I mentioned above, we have 700 million years of ocean history recorded in the fossil record, especially in the deep-sea cores that record the past 100 million years in great detail. We can analyze the carbon isotopic composition of shells of planktonic microfossils and show how the ocean chemistry has changed. We can look at the patterns of diversity and extinction of acid-sensitive marine fossils, and find out when the ocean has experienced this kind of “acid bath” before. As a recent article by Hönisch et al. (2012) pointed out, the current episode of mass extinction and rapid acidification of the ocean has no precedent. The closest we can come to is the worst mass extinction in earth history, the “Great Dying” at the end of the Permian Period, about 250 million years ago. The extinction was so severe that about 95% of marine species vanished, and a similar number of land species as well. Although the complete causes are complex and still under discussion, there is a clear signal from the chemical isotopes that there was a global warming event, as well as too much carbon dioxide in the seawater (hypercapnia). It is thought to have been driven by the largest volcanic eruption in earth history, which occurred in northern Siberia. As these eruptions released greenhouse gases, they drove the delicate chemical balance in the oceans to supersaturation in carbon dioxide and highly acidic conditions. Between the toxicity of hypercapnia and the effects of dissolving shells, nearly every group of animals in the oceans vanished 250 million years ago. These included many groups, such as rugose and tabulate corals, trilobites, and blastoid echinoderms, that had survived many previous oceanic mass extinctions. Other groups, such as the brachiopods, the bryozoans, the crinoids, the bivalves and gastropods, and the ammonoid cephalopods nearly vanished, with only a few subgroups surviving to repopulate the world later.

The fossil record provides us with a sobering lesson: what we’re doing to our atmosphere is bad enough, but what we do to the oceans is even deadlier, even if it is less visible to us landlubbers. Previously, all the focus has been on the mass extinction in land animals caused by humans and their associated animals, but the devastation of the oceans is far worse. The last time it was this bad, life nearly vanished from this planet.

31 Responses to “Shifting Baselines and Dying Oceans”

  1. CrookedTimber says:

    Nice post Donald. A little disheartening for a beginning diver such as myself. I will be visiting the reefs around the Bay Islands of Honduras later this winter.
    Ed Yong recently linked to this post about the same subject which makes the science sound a little less clear cut (although still dire). I would be interested in your thoughts.

  2. MadScientist says:

    Ah, so it has a name: shifting baselines. Years ago someone told me that they had been to a particular reef and that it was gorgeous – I said it was nothing like it was 30 years ago and I thought it was an awful shadow of what it once was. People who had never seen these ecosystems in better conditions are still awed by them but don’t realize how much they’ve degraded.

  3. tmac57 says:

    Interesting. Donald has posted an article about the effects of AGW ,and yet their isn’t (yet) the usual landslide of counter talking points that usually follow an article concerning such a topic. Maybe this is a good sign…we will see.

  4. dragonfly says:

    I am definitely not a climate change skeptic. Unfortunately, I am not an expert on the subject.

    I was confused by this opinion piece in the Wall Stree Journal today:

    Is anyone familiar with Matt Ridley and Nic Lewis’ work? I have viewed the IPCC as a valid source of information on climate change and was surprised by the strong criticism of it in this article.

    Thanks for any background information.

  5. tmac57 says:

    Want to know more about Matt Ridley? Try this:

    By the way,the WSJ has a poor track record when it comes to presenting unbiased information about AGW…just sayin’

  6. Canman says:

    Here’s my solution:
    although I’d nix the windmills in favor of quick and dirty nuke plants. It’s a huge frozen wasteland for Chrissakes!

    Also, I wonder if there are small concentrated areas of the oceans, where the problem is acute, that could be limed or something.

  7. Canman says:

    And … and could these living coral reefs be genetically modified by Monsanto or something?

    • markx says:

      Cheers, Canman! I’m not so welcome here, so shall depart the scene. Seasons greetings to you and yours, sir!

  8. tmac57 says:

    “stick to the science” as defined by whom…a handful full of contrarians,as opposed to the vast majority of climate scientists and academies of science the world over?
    Hmmm…tough choice.
    Markx you are truly delusional.

  9. tmac57 says:

    Uh oh…looks like someone got pulled over for trolling.

  10. markx says:

    Perhaps you could leave this one in for a while, Donald.

    You will undoubtedly be pleased to hear I will no longer participate in this forum.

    I do try to put up scientifically referenced discussions on the CAGW theory, even though I don’t necessarily believe the theory is wrong. It is simply my personal belief that 20 or 30 years of detailed climate recording when combined with a lot of proxy and modeling data do not constitute settled science.

    I agree with the fact we should be reducing our dependence on fossil fuels. I disagree with the the scientists, economists and politicians who are clamoring for an immediate solution.

    Time will tell. Hasten slowly and with knowledge.

    Thank you for those who have discussed issues with me, I do appreciate people like tmac who do read, think and discuss (in spite of his predilection for quoting the abominable Skeptical Science pages!)

    Best regards and seasons greetings to all. Mark.

    • tmac57 says:

      “in spite of his predilection for quoting the abominable Skeptical Science pages!”

      And yet you find WUWT to be a fount of sound information on climate science. I think a one to one comparison of those two sites by anyone with a functioning brain can spot the true abomination.

  11. Canman says:

    I would really like to hear a precise definition of climate change denier.

    • Canman says:

      I have no idea how this comment got posted as no. 12 ahead of 13 through 16.

    • tmac57 says:

      I’ll answer with my personal take on this.
      A climate change denier ignores the current consensus of climate scientists in favor of a strong bias toward a small group of contrarian opinions on AGW,and also picks and chooses out of context data points that only seem to support their position,while blithely discounting mountains of data that disagrees with their position.
      Basic tools of the denier:
      confirmation bias
      motivated reasoning
      strawman arguments
      ad-hominem arguments
      conspriacy mongering

  12. Mal Adapted says:


    “You will undoubtedly be pleased to hear I will no longer participate in this forum.”

    Aww, stick the flounce, sweetie.

    “It is simply my personal belief that 20 or 30 years of detailed climate recording when combined with a lot of proxy and modeling data do not constitute settled science.”

    Of course personal belief trumps evidence any time, and expert consensus never had a chance. Seriously, do you realize what you’re saying? Look up the (let’s see if html will work in comments) Dunning-Kruger effect

    • markx says:

      You’d flounce too, well named Mal, if you went to all the trouble of reading referenced research papers and had well reasoned replies deleted for “trolling”:

      Here – you seem to be on line, this may stay up for a minute or two:

      My researched and referenced posts were all deleted in short order. The new definition of “trolling” is apparently ‘disagreeing with the author’.

      Perhaps there is a degree of embarrassment by the author, Donald Prothero that he had not bothered to read in any depth the reports he was quoting: eg

      These reports are simply about the natural phenomenon of the Carbonate Compensation Depth, the depth below which carbonate shells cannot exist (about 4000 m) and the natural upwelling of this ‘shell corrosive’ water. The researchers then simply apply some forecast pH and temperature data to this via modeling and come to the rather obvious conclusion that the process will become worse(?)/more common if pH and temperature increase in the future.

      (Although, perhaps it is not quite so obvious): “…The exact value of the CCD depends on the solubility of calcium carbonate which is determined by temperature, pressure and the chemical composition of the water – in particular the amount of dissolved CO2 in the water. Calcium carbonate is more soluble at lower temperatures and at higher pressures….”

      • markx says:

        correction “..if pH and temperature increase in the future…” should read “…if ocean acidity…”

  13. Canman says:

    I would like to note that I commented in the comment policy on Markx’s comments being deleted:

  14. Sancho says:

    Could all these changes be caused by submarine volcanoes? Perhaps, supervolcano eruption, not yet detected.
    If it was deep >1500 and far from any landmass, the detection would be very difficult. The effects of such an event could at least partially be attributed to what is happening to the oceans.

    • Donald Prothero says:

      Sorry, no. Supervolcanoes are easy to detect by their seismic signature (we have a worldwide seismic network that picks up even the smallest quake anywhere in the world), and we’d have heard about it if they were happening. Almost all the supervolcanoes we know about are well documented, and none has erupted on land or under water since Toba about 71,000 years ago.

      • Sancho says:

        I disagree. Not all volcanoes erupt explosively, some of them just release magma slowly. Slowly erupting submarine super volcano would not be easily detectable. It could be at a depth of 5000m or more and water pressure would prevent an explosive eruption.
        In the meantime the effects of such an eruption could manifest itself with raising temperature and increased acidity of the ocean above.
        This in fact is happening at a smaller scale along the Atlantic ridge. I hypothesize something like this happening, only much bigger magnitude. Perhaps somewhere in the middle of Pacific.
        It happened before:

  15. tmac57 says:

    Here is a press release for that study:

    See if it implies anything other than AGW is causing warmer and more acidic oceans,and that it is negatively affecting marine life in the Southern Ocean. Only if you cherry pick what you want to hear.

  16. MadScientist says:

    If they survive the warming, the ocean acidification will get ‘em. Corals, unfortunately, are rather sensitive to the environment.

  17. tmac57 says:

    I can’t comment on it,as I have not had a chance to study the issue yet.But,having said that,I still believe that you misunderstood or misrepresented the article about the Southern Ocean.You obviously don’t see it that way,so I will leave it to other readers to decide who is cherry picking.

  18. Mal Adapted says:

    Heh, heh — now Markx is getting himself schooled over at SkepticalScience. Markx, you seem to be unclear on the skepticism concept. You’re getting a graduate course over there. I hope you take advantage of it.

  19. markx says:

    Perhaps a few will read this before I get the chop there and see how Skeptical Science conducts debates:

    Mod (at SS): Allegations of impropriety? You must have a different dictionary than the one I have:

    And you are also protecting the EPA from criticism?!!!!

    Here is what I said: Perfectly reasonable statements of fact, no criticism intended.

    markx said (and got snipped):

    It became a political discussion from the first few comments, probably (and to tie it into the article) from the approach in the article that Ridley’s motivation must necessarily be political: “Ridley is optimistic that human enterprise and ingenuity will be sufficient to sustain our upward progress, but just so long as “parasitic” governments don’t prevent us from conducting business as usual.”


    “Legislation via regulation” is beginning to predominate.

    The EPA have made some rather incredible leaps in statistics with the millions of people they will save from particulate and mercury poisoning deaths and used those figures to justify regulations which will have the effect of shutting down energy suppliers.