I’m Confused About Coral, or Maybe John Cook Is

My last post mentioned I had decided to read a book John Cook was a co-author of, Climate Change Denial: Heads in the Sand. I quickly found a significant amount of the book had been copied and used in another book by Cook’s co-author (Haydn Washington’s Human Dependence on Nature: How to Help Solve the Environmental Crisis). Unfortunately, I couldn’t find an eBook version of it, and I didn’t care to spend $40+ of my own money for a physical copy.

To add to the problem, I found out Cook was a co-author on another book, Climate Change Science: A Modern Synthesis. Happily, I was informed the Springer publishing group would give out free copies of this book to bloggers so I wouldn’t need to buy it. I registered with the company’s website, got an eBook copy and began reading.

I began by looking at the plagiarism issue just to see how much copying happened in these books. I’m not sure if self-plagiarism like Washington’s is “wrong” or not, but it is certainly a matter of interest to people who might buy the books. Before I could get to that though, I stumbled across a number of oddities. Many merit discussion, but the one I want to highlight right now can be seen below:


This section is titled, “More Fossil Fuel Carbon in Coral,” but it never mentions coral. It refers to plants with this misleading statement:

Plants prefer carbon-12 over carbon-13. This means the ratio of carbon-13 to carbon-12 is less in plants than it is in the atmosphere.

This statement is misleading because not all plants prefer “carbon-12 over carbon-13.” Many plants do not discriminate much (if at all) between types of carbon.* Two major examples are corn and sugar plants. I’m not sure how this book manages to make a claim about plants as a whole despite it being false for such major crops, but… whatever. That’s not the part which really confuses me.

The part that confuses me is, where’s the discussion of coral? Do the authors believe corals are plants? If so, they’re wrong. Humans realized corals aren’t plants in the 18th century. Are the authors just unaware of this basic fact?

I get corals “eat” plant life. I get the carbon ratio of a plant can travel up the food chain and be present in any animal on the planet. I even get the carbon ratio in various animals depends on what plant life they eat (as not all plants prefer carbon-13 over carbon-12).

What I don’t get is what this section tells us about corals. It doesn’t appear to discuss corals in any way, unless the authors foolishly believe corals are plants. I suspect they do. In 2010, one of the authors of this book, John Cook, published this on his website:

The most common carbon isotope is carbon-12 (12C) which is found in roughly 99% of the carbon dioxide in the atmosphere. The slightly heavier carbon-13 (13C) makes up most of the rest. Plants prefer carbon-12 over carbon-13. This means the ratio of carbon-13 to carbon-12 is less in plants than it is in the atmosphere. As fossil fuels originally come from plants, it means when we burn fossil fuels, we’re releasing more 12C into the atmosphere. If fossil fuel burning is responsible for the rise in atmospheric CO2 levels, we should be seeing the ratio of 13C to 12C decrease.

This text is nearly identical to that found in the book, and it is found in a post titled, “The human fingerprint in coral.” It never explains why it only discusses plants in a post about corals, when everyone knows (or should know) corals are not plants.

I suspect John Cook genuinely believe all “plants prefer carbon-12 over carbon-13” even though that’s only true for some plants. I suspect John Cook genuinely believes corals are plants even though humans have known better for hundreds of years. I suspect John Cook simply doesn’t know what he’s talking about.

*Some might even prefer carbon-13 over carbon-12. I’m not sure as I have only a limited experience in biology. If anyone knows more, I’d be happy to hear from them.



  1. Corals are animals, yes, but have symbiontic algal cells called zooxanthellae embedded in their tissues. Algae are plants in the sense that they photosynthesize, although modern classification finds them different enough from land plants to assign them to different branches of the tree of life. Cook probably is referring to these cells which exist in a mutualistic relationship with the coral. See https://en.wikipedia.org/wiki/Symbiodinium for details. I haven’t read the book so I’m taking your word for the skimpy reference. He could have been clearer about the situation. That he wasn’t speaks both to ignorance of the author and to shoddy editing.

  2. Gary, the screenshot I provided is the entire section. The section after that is, “Shrinking Upper Atmosphere,” and it is only two sentences long. The section after that, “Less Oxygen in the Atmosphere” is only one sentence long. The section after that, “More Fossil Fuel Carbon in the Atmosphere has only this sentence:

    See “More Fossil Fuel Carbon in Coral” above.

    I can screenshot the sections if anyone is interested, but calling them “skimpy” is being generous.

    As for the plant vs. animal issue, I get there are things which are sort of plants which are sort of related to corals. I don’t think that justifies anything in the book though. The same sort of “plant” life is found in jellyfish too. Nobody would claim jellyfish are plants.

    This book claims to be written as a college textbook. If I, a person with no biology education beyond a single class in freshman year, can spot problems like this, there’s a huge problem. I’m not asking for perfection. I’m just asking people know something about the subjects they’re teaching.

  3. I suspect it’s just a copy-paste job gone wrong. they forgot to include the rest of the 2010 post, where the point about corals providing a window in the past

  4. I’m with omnologos — reading the original article makes clear that Cook uses the fractionation found in corals as a proxy for the atmospheric proportion of C13.

    Now it’s also true that coral uptake of carbon discriminates between isotopes, and other factors affect the C13 fraction found in corals. But that would disturb the “nice tidy story.”

    In this case, I happen to agree with Cook that fossil fuel burning is the major cause of pCO2 increase. But his superficial discussion is why I characterize SkS as “not necessarily wrong.”

  5. omnologos, HaroldW, I don’t doubt “Cook uses the fractionation found in corals as a proxy for the atmospheric proportion of C13.” My problem is I don’t see anything which indicates Cook understands the topic.

    It seems a case where he’s referring to something real without actually understanding it. Even the Skeptical Science post fails to explain how one goes from “plant” to “coral,” implying corals are plants.

  6. Okay there’s a major issue here with the discussion re plants. Cook is absolutely right in saying that all plants strongly discriminate against carbon-13. However the degree of discrimination varies with the photosynthetic pathway. C3 plants are the strongest discriminators and have the lowest d13C isotope values. C4 plants, as alluded to by Brandon when he mentions cane sugar and maize, also discriminate against carbon-13 but by not as much as C3 plants. As an illustration C3 plants have delta13 C values of between about -18 and -32 per mille, and C4 plants have values of about between -12 and -20 per mille. These are all negative with respect to atmoispheric CO2 which is about -8 per mille.

  7. Paul Dennis, thanks for your comment. I spent a bit of time reading more about this topic in the last few days. It’s kind of interesting. One thing I thought was particularly interesting is apparently there is a push to try to convert rice from a C3 to a C4 plant. If that happens, I think it’d be a big deal due to the increase in efficiency. I have no idea how likely it is to happen (or when it might happen), but I am intrigued. I have to wonder if people would condemn it like they do GMOs though.

    Anyway, I think what you say is right so it really just comes down to John Cook failing to explain what corals have to do with plants. That’s not a huge failure, but it creates the impression corals are plants, something which is just silly.

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