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Climate Hustle

CO2 is Good for Plants: Another Red Herring in the Climate Change Debate

Posted on 1 July 2010 by Mariana Ashley

Guest post by Mariana Ashley

CO2 feeds plants. And so, too, does ignorance and a little bit of politicking feed inane misconceptions. Rep. John Shimkus of Illinois made famous the CO2 as plant food argument during a U.S. House Subcommittee on Energy and Environment hearing in 2009. The basic plant food argument is that since plants need CO2 to grow, more CO2 means, by proxy, more sustained and robust plant growth globally.

A quick look at the science behind this argument demonstrates its inherent weaknesses. In closed, controlled environments, like greenhouses and plant nurseries, an increase in CO2 does indeed spur plant growth. However, the globe is not a controlled environment, and it’s incredible sensitivity to a variety of factors is something that is often taken for granted when such narrow arguments are proffered. A rise in CO2 levels is not the only consequence of climate change, and it is these other effects that have had and will have more abiding adverse effects on plant growth around the world.

While CO2 is an important element that stimulates plant growth, the planet's flora requires a cocktail of elements to maintain its health. Arguably the most important of these elements is water. With the global increase in temperature caused by the various factors affecting our climate's balance, increased evaporation means decreased soil moisture. Another effect of global climate change is erratic precipitation patterns. This causes extreme weather in certain geographic locations only sporadically, with overall, balanced rainfall drastically reduced.

Suppose, however, that CO2 does prime plant growth in the world at large. To what extent will this happen? For one, the increased density of forest vegetation could increase the risk of wildfires, which have reared their ugly heads in California all too often in the past few years, wreaking devastating damage. Presumably the CO2 as plant food enthusiasts offer their argument in an effort to demonstrate the resulting agricultural advantages. But even if "CO2 fertilization" occurs, weeds proliferate in tandem with crops, which would only increase the global cost of agriculture.

We could discuss the scientific finer points of global climate change and the unlimited effects it could have on global plant growth all day. A Climate Denial Crock of the Week video does just that in debunking the CO2 plant food argument. However, at its most basic level, the CO2 plant food argument rests on a simple logical fallacy--the fallacy of exclusion, which focuses on one cause-and-effect (in this case, more CO2 means more plants) to the exclusion of all other cause-and-effect chains.

When CO2 is framed as an element good for plants in order to dismiss the other existing pieces of evidences that suggest the dangers of global climate change, we are left with an idea that only distracts us from the more pressing issues of our planet's increased loss of balance.

This guest post is contributed by Mariana Ashley, who writes on the topics of online colleges. She welcomes your comments at her email:

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Comments 1 to 50 out of 104:

  1. Wouldn't that be "...the planet's flora requires..." instead of "...the planet's fauna requires..."?
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    Response: Indeed, I hope Mariana doesn't mind that I've gone ahead and corrected this error. Thanks for the tip.
  2. Well, yes, some of us are really tired of hearing that nonsensical line, "CO2 is good for plants". After all, water is good for them too, but too much water still kills them. Even when it doesn't kill them, it can still cause poor development of the plant's root system.

    Both water and CO2 have to be made available to the plant at the right time and in the right quantities; going outside of either one can be very damaging.

    THAT is the real principle ignored by the "CO2 is good for plants" crowd.

    Surely pointing out this real principle is more effective than using language like 'proferred'! Mariana seems to have forgotten both the depth and the character of anti-intellectualism among the very people she is trying to persuade: use of fancy language like 'proferred' is likely to shut their ears before they have given her a fair hearing.

    Actually, come to think of it, there is another principle Mariana is ignoring: taking it into account could enable her to remove much of her post and write something more compact and hard-hitting instead. And this is a principle the "CO2 is good for plants" crowd has even more conspicuously ignored. That principle is that plants 'breathe in' CO2 during the day, but breathe oxygen at night: they are net consumers of CO2 ONLY while they are growing. Once they stop growing, they no longer remove CO2 for us.

    Unfortunately, this second principle is not common knowledge; at least in the US when I was in high school, science classes commonly mentioned that plants consume CO2, but I never heard their consumption of oxygen mentioned. Nor am I alone. Only their consumption of CO2 is common knowledge.

    Finally, answering KR: what she said about the fauna is also true of the flora, it is not obvious which would actually be stronger for her argument. I suspect she really meant what she wrote, since the fauna (including us) are more sensitive to variations in that 'cocktail', variations caused by AGW, possibly amplified by the plant growth assumed.
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  3. "That principle is that plants 'breathe in' CO2 during the day, but breathe oxygen at night: they are net consumers of CO2 ONLY while they are growing. Once they stop growing, they no longer remove CO2 for us."

    They only consume a small amount of oxygen. Not to mention it's not night all over the globe at the same time, so it's not like every plant on the face of the earth is consuming massive amounts of oxygen all at the same time.

    So your point is?
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  4. A strength of this website is that it gives several relevant links to the academic literature.

    While I understand that the point being made here is a simple logical one, moreso than a discussion of the underlying science, I suggest providing some citations here, as well.
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  5. I posted links to a few references in my comments on the CO2 Is Not a Pollutant thread.
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  6. A slightly off topic point.

    Lord Monckton is, as far as I know, the originator of the "Carbon Dioxide is FOOD for plants" meme. For a while I thought that he was being ignorant in mixing up the sense of food and air. After all CO2 was obviously "air" for plants. "Food" would be either fertilizer for your roses or decomposing plants and animals on the Forest floor.

    Then I got to know the man better and noticed what a subtle manipulator he is. I realized, in a flash, the psychological brilliance of calling CO2 "food" for plants.

    If CO2 where to be correctly identified as "air" for plants then no one would care. The reason being that we take air for granted in spite of our inability to do without it. "Food", on the other hand, is constantly on our minds.

    It is a clever Propaganda sleight of hand. If John Q. Public should mention this "food" meme, we should respond to before we even get into any mother explanations.

    Since it is easy to explain the difference between air and food, our gently correcting Mr. John Q. Public should create the first subtle hints of doubt in his mind.

    Yes, I know, it's not logically relevant but if we are to communicate with people better then we have to know the difference between the psychological and the logical.
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  7. Hmm, that's a good point, villabolo. It's like saying oxygen is "food for humans", which anyone can see is false. Thanks for pointing that out.
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  8. Rather than simply taking the quick look at the science behind the argument as the author believes is all that is necessary, perhaps a detailed study of the real world, and the real world trials, such as the FACE trials, which are not mentioned, that replicate projected growing conditions, including enhanced atmospheric CO2, higher temperatures and lower moisture levels would be even more enlightening.

    Perhaps even looking at the results of trials that studied how plant growth responded to depleted CO2 levels would bring even better understanding as to the central role CO2 plays as a growth regulator.

    The arguments against increased CO2 being a positive for plant growth seems to be based on a belief that the current balance of inputs that plants require is optimum, each in the correct ratio.
    Commercial greenhouse growers know that that is not correct. Even if they provide sufficient warmth, nutrients and moisture, the full growth potential is not achieved until the CO2 levels are increased to optimum levels as well.

    Perhaps the next time anyone visits a supermarket and salivates over the well grown fresh produce, and admires the beautiful flowers, just check out how much of what has been admired, or has been put onto your dinner plate in recent decades has been grown in an enriched CO2 environment.

    The examples of the negative aspects only illustrate a lack of appreciation of the real world.
    What weeds in agricultural crops love even more than CO2 is nutrients, especially nitrates, and most cropped land has been stuffed full of nutrients. One of the biggest inputs into cropping is weed control, and any competent farmer is gradually reducing the weed seed bank, with genetic modification helping produce crop varieties that are more and more resistant to herbicides.
    Whether in the past, now or in the future, any farmer who has not overcome the weeds before the crop is planted will not be viable for very long.
    From an Australian perspective, over the last 50 years, the amount of cereals produced per acre has risen to nearly 3 times the previous level. It is anticipated that the same increase can occur again over the next 50 years even allowing for climate change.
    That means that the area of weeds that need to be controlled is dramatically decreasing for the same amount of food harvested. That seems more like a positive rather than a negative.
    As far as the supply of nutrients go, irrespective of any other factors, to produce more food, more nutrients are required to be put into the growing system, that is a basic truth.
    If the argument is made that the supply of nutrients will not allow the increased growth due to CO2 fertilisation, then there will also not be enough nutrients to support increased food production even if CO2 levels remained constant, or even fell.
    Being able to put more nutrients onto a smaller unit of soil to produce even higher yields is a positive both for efficiency of nutrient usage and application.

    OT a bit, but the biggest challenge is that for every 20,000kj per person per day that is produced in the paddock, only about 8500kj ends up on a persons plate. The more developed the society, the greater the wastage, little ever being returned to be recycled productively, huge amounts instead making it into landfill, decomposing to produce CO2 and methane.
    Lamenting over whether there will be sufficient nutrients to support increased growth due to CO2 is misplaced whilst such wastage is allowed to continue.

    The IPCC states that globally averaged mean water vapour, evaporation and precipitation are projected to increase, though there may be some shift in rainfall patterns. For Australia, in the areas where the rainfall is projected to decrease, the IPCC project a decrease in evaporation of the same magnitude if their Fig.10.12 is any indication.

    As for the wild fires, the argument is not even relevant, a red herring if ever there was one.
    Wild fires only present a problem when humans choose to settle in the areas prone to fire and build inappropriate infrastructure that is unable to be defended.
    Fires are a natural part of most landscapes, and where mankind is upsetting the natural cycle is not by allowing fires to burn, but by putting out the fires that would burn more frequently in less extreme conditions keeping fuel loads lower.
    This interference means that when a wild fire does start that is unable to be controlled, the higher fuel loads, and the fact that the conditions are generally more extreme, the results are even more devastating.
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  9. villabolo at 11:00 AM, I doubt that Monckton is the originator of the CO2 is food for plants "meme".
    The technique has been in commercial use for decades and is well understood by agricultural experts. It is only the focus on CO2 atmospheric levels rising that has over the last couple of decades caused them to conduct trials to see if what was being done artificially by commercial operators will be replicated under real world conditions.
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  10. Wow, what an incredibly long post to say almost *nothing* of value John D. You keep banging on about how *wonderful* the FACE trials are in showing that increased CO2 is a good thing, yet the Horsham trials you rely on show that-even in relatively optimum conditions (in terms of water & nutrients)-there was no significant improvement in grain yield for most varieties, a significant decline in protein yield & an increased demand for nitrogen by plants grown in the enhanced CO2 conditions. As nitrogen is one of the biggest costs facing farmers, this hardly represents GOOD NEWS for the farming community-which is probably why the investigators themselves are so circumspect about their findings-especially given that they were starting to see acclimation just a couple of years into the trial. Given that CO2-induced warming is also expected to cause declines in rainfall, then the prospects for enhanced agricultural output in an enriched CO2 world are looking far grimmer than you'd have us believe.
    The fact, Mr D, is that until you're prepared to provide more substantial REFERENCES to back up your claims, then people will dismiss you as yet another denialist who gets all his (mis)-information from Monckton et al.
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  11. Perhaps the next time anyone visits a supermarket and salivates over the well grown fresh produce, and admires the beautiful flowers, just check out how much of what has been admired, or has been put onto your dinner plate in recent decades has been grown in an enriched CO2 environment.

    Drawing on your expertise, would you please produce some statistics on what we might expect in that department, John? Typically speaking, when I visit my grocery here on the West Coast of the US, what might I expect to see in terms of fruit and produce grown as you imply is common? Depending on the season we typically in a week purchase zucchini, celery, lettuce, tomatoes, potatoes, broccoli, onions, garlic, asparagus, apples, plums, peaches, bananas plus of course other vegetables and fruit. Of the foods I've named, what percentages would I expect to have been grown in enhanced C02 environments?
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  12. I would like to add here that there is a need for a more information on the various photosynthetic pathways for various plants i.e. C3, C4 and CAM. Ultimately how elevations in CO2 can be positive in some instances and negative in others. The negatives being erratic growth of certain food producing plants, and the impact on biodiversity and ecosystem services associated with increased CO2. Anyone have any expertise in this field?
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  13. Yet again you miss the point John D, its becoming an increasingly bad habit for you. Every time you bring up this issue, you fail to answer the key questions:

    1) does an enriched CO2 environment generate long-term, increased plant growth in the absence of ideal conditions?

    2) does an enriched CO2 environment generate a significant increase in the quantity of *edible* biomass (usually seeds or fruit)?

    3) does an enriched CO2 environment generate a significant increase in the nitrogen content of the edible biomass?

    4) does an enriched CO2 environment lead to a decrease in demand for other limiting factors (like fertilizer & water)?

    5) does an enriched CO2 environment have any other positive or negative impacts on cropping *in the real world*?

    Based on the experiences of the farmers I work with, & the results of the Horsham trial you love so much, the answers to those questions are:

    1) No. Improvements have been shown only in the short term, & only under ideal conditions.

    2) No. In most cases only the vegetative biomass has shown significant increase, wheras edible biomass has shown no significant increase.

    3) No, the Horsham trials actually show a significant decrease in plant protein yields.

    4) No, the Horsham trials actually show that plants grown under enriched CO2 have a *greater* demand for nitrogen than plants grown under regular conditions.

    5) Yes-increased CO2 is resulting in global warming which-in turn-is leading to a general decline in fresh water availability (Autumn rainfall in South Australia alone has dropped by 30% in the last 30 years). Increased CO2 will also cause increased vegetative growth in weeds, which will place further cost constraints on farmers in terms of weed control &/or fertilizer/water.

    So you see that your arguments really don't stand up to close scrutiny Mr D. Its also worth noting that the people that I encounter who are *most* concerned with Global Warming are the farmers I collaborate with-many of whom have worked the land for 30 years or more. If increasing CO2 in the atmosphere was so good IN THE REAL WORLD, then why are so many farmers having an increasingly tough time in maintaining a viable enterprise?
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  14. villabolo:

    I don't know if it's worthwhile or instructive to get into semantic arguments over whether a necessity counts as "food" or not. There are better things to worry about.
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  15. So, according to my admittedly brief reading on the FACE trials, the yield gains from a doubling in CO2 are 5%-7% for rice, & 8% for wheat. Of course this takes no account for the potential shortening of growing times-or reduced rainfall-caused by global warming. Nor does it take into account the reduced protein yield that was shown in the Horsham trial, & previously shown by Ziska et al (1997). Seneweera and Conroy also showed-in 1997-that plants grown in CO2-rich environments show decreased uptake of both iron & zinc. Given that the Horsham trial also showed an increased demand for nitrogen by wehat, such a small increase in yields is not going to sell farmers on the "benefits" of global warming.
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  16. Marcus, one more key question to ask:

    Q 6) Do the elevated CO2 trials also elevate ambient temperature commensurate with the test levels of CO2?

    A 6) No, they do not.
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  17. The funny thing about this whole "CO2 is Plant Food!!!" malarkey is that the science showing it's rubbish is from the early 19th Century: Liebig's Law of the Minimum

    In summary: its no use increasing one factor which contributes to plant growth without increasing the other factor proportionately.
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  18. That should be "factors proportionately".
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  19. I like the "CO2 is good for plants" argument. Especially when you put it alongside the "CO2 is present in such small concentration in the atmosphere that it can't possibly do anything" argument.

    However, I'm quite happy to concede the "CO2 is good for plants argument". Its pretty much the same as the "at least he made the trains run on time" argument for Mussolini.
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  20. Jim Eager-that's exactly my point. The FACE studies *only* replicate the increase in CO2, not the commensurate increase in warmth (which leads to a shorter growing seasons) & decrease in fresh water availability (increasing the likelihood of plant stress & reduced yields). Even without including these factors, the FACE studies have shown only the most marginal increases in overall yield, yet these same studies have shown a decrease in quality & an increase in the cost to produce it (due to increased demand for nitrogen).
    Like I said, John D's argument is looking pretty flaky about now!
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  21. Links appear broken.

    Also, I believe I remember a small controversy about some stunted tree growth of the past few decades...
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  22. Increased CO2 improves plant growth.
    Warmer temperatures mean longer growing seasons, which means more plant growth.

    Therefore, the midwestern U.S. in the 1930s, which had both warmer temperatures and higher CO2 than previous decades must have been great for agriculture. QED.

    Oh... wait...
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  23. Yes, apescape, that would be the result of increasing drought, which is causing trees to grow less each year-in spite of warmer conditions & higher CO2 overall. Another nail in the coffin of the CO2 is plant food argument.
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  24. The CO2 is plant food dates back at least to 1988 with
    Environmental Effects of Increased Atmospheric Carbon Dioxide - ROBINSON, BALIUNAS, SOON AND ROBINSON [may be a little slow] of the Oregon travesty of a Petition.

    [Final Paragraph from this document]
    Human activities are believed to be responsible for the rise in CO2 level of the atmosphere. Mankind is moving the carbon in coal, oil, and natural gas from below ground to the atmosphere and surface, where it is available for conversion into living things. We are living in an increasingly lush environment of plants and animals as a result of the CO2 increase. Our children will enjoy an Earth with far more plant and animal life as that with which we now are blessed. This is a wonderful and unexpected gift from the Industrial Revolution.

    I haven't yet delved into the references regarding this.
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  25. Oops 1988 typo! Should be 1998!
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  26. John Cook, I love you. Who else could find such comical stuff. Here is a nice little animation which I am sure most of your readers are familiar with:

    Mariana, you will no doubt claim that this is a laboratory experiment with no relevance to the real world. Guess what? Duke University and NASA took the experiment out doors into the Duke forest in North Carolina:

    The FACE experiment showed a dramatic increase in the rate of plant growth stimulated by CO2 until limitations in other nutrients kicked in.
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  27. I have always had sympathy for plants as they have to survive with such a low atmospheric concentration of CO2. Concentrations have been as low as ~200 ppm but now are (mercifully) approaching 400 ppm.

    Then it struck me that fish are more deserving of my sympathy as they are trying to survive in water that always has less than 10 ppm of oxygen.
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  28. You may be interested in the Bookhaven FACE Research (Free-Air CO2 Enrichment) site. There is an extensive publications list there and also links to all the FACE research sites around the world.

    EuroFACE has a brief RESULTS page and lots of online publications as well. Explore, enjoy.
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  29. @galloping camel,

    I checked the website and the "F" in FACE stands for "forest". It is not clear if the results are transferable to large scale commercial growing of vegetables for consumption, where some key nutrients may be under stress.

    The video seems to show a replicated experiment where all factors except one (CO2) are kept constant, possibly at a generous level. Interesting, but a poor experimental design and too simplistic to be conclusive.
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  30. Logical Science has a collection of studies onThe CO2 will fertilize the plants and increase food production meme.

    There is also additional scientific evidence for increased CO2 resulting in:
    a) Increased toxicity

    b) Reduced protein levels
    Effects of elevated CO 2 on the protein concentration of food crops: a meta-analysis - TAUB et al. 2008
    c) Increased toxicity and reduced nutritional value
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  31. About the only statement I agree with in this rather dismissive post is “the globe is not a controlled environment, and its incredible sensitivity to a variety of factors is something that is often (not considered) when such narrow arguments are proffered”. Using the same logic laboratory scale experiments on the effects of CO2 and temperature on coral and other marine creatures should also be assessed with a grain of salt (excuse pun).
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  32. The 'fallacy of exclusion' link doesn't seem to work.
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  33. Gallopingcamel, do you actually ever bother to *read* the results of these studies? Have a look at the results of one of their papers, where they find "...that elevated CO2 increased disease incidence and severity in two Cercospora leaf spot pathosystems in some years." So much for CO2 being a good thing. What is of far greater importance for tree growth is *not* CO2, but access to *WATER* & *GOOD CLIMATE*, neither of which were properly simulated in the FACE studies you refer to!
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  34. A comment to #6 villabolo and #7 Bern:

    Animals and humans use oxygen primarily to get energy to keep us going through the day. Plants use CO2 to keep building biomass. They get energy from sunlight. Therefore it is more correct to call CO2 "food" for plants than "air" for plants. CO2 does not give them energy.
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  35. I did a bit of research into the way glasshouse growers use CO2 to boost plant growth.

    To simplify; as one would expect, CO2 levels in greenhouses fluctuate throughout the day as the plants 'breathe' both oxygen and CO2. It appears that higher concentrations of CO2 do help growth at certain times of the day when, in glasshouses, CO2 levels would sink below levels that would otherwise pertain outside in the open air.

    QUOTE: "The best time to add CO2 is from dawn to dusk. CO2 ranges from 400 to 500 ppm during the night due to plant respiration. Right after sunrise a level will drop to about 300 ppm. After three to four hours of early sun light it will drop to 100 to 250 ppm at which time growth will stop. If you add CO2 during the winter months when ventilators are closed and CO2 concentrations are low, you will get increased yield and bloom which normally happens during the spring and summer."

    The above quote is from Advance Greenhouses

    Perhaps the issue is not as straightforward as some people think. Modern plants have evolved to grow at their 'ideal' rates in the CO2 concentrations that have pertained in the atmosphere over the last 100K+ years. Increased CO2 concentrations can only affect growth in a useful way when plants are in artificial conditions controlled by humans and 'quantity not quality' is the human goal. Could wild plants subjected to increased CO2 levels become susceptible to other problems? For instance could too-rapid growth make them structurally weak and unable to support themselves properly -- so that they're more likely to blow over in a gale? Something like this might not matter in a greenhouse but it would matter in the wild.

    There's also the point -- hinted at in the quote -- that higher levels of CO2 could lead to inappropriate growth at times when the plant should be resting. This is OK for a greenhouse plant whose destiny is to be eaten -- not so good for a plant that needs to survive and reproduce in the wild. Yet another damaging effect of climate change.
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  36. doug_bostrom at 12:17 PM, doug you should take the opportunity to check back from where you shop and see where it leads to.

    This paper may provide some historical background for you. It was written by SYLVAN H. WITTWER, professor emeritus of horticulture at Michigan State University. He directed the Michigan Agricultural Experiment Station for 20 years, and chaired the Board on Agriculture of the National Research Council. He is the author of the world's leading textbook on greenhouse vegetables, at least in 1992 when this paper was written.
    An extract from the paper to whet your appetite:-
    "American commercial greenhouses have used carbon dioxide fertilization for tomatoes, lettuce, cucumbers, flower and foliage plants, and bedding plants for at least 30 years. The benefits of this enrichment were first discovered by nurserymen in Germany 100 years ago, and the practice is widely used in Sweden, Denmark, Holland, Germany, Australia, and Japan, as well as the United States and Canada."
    Rising Carbon Dioxide Is Great for Plants
    by Sylvan H. Wittwer

    What I think is forgotten by many who are adept at Google searches and cutting and pasting, is that not everything is available on the internet. A lot of what I have read over the years comes from industry specific publications and describes what is actually happening in the real world. It may be years, perhaps never, that it makes it to the stage of being published in a peer reviewed journal and becoming available on the internet. But that doesn't stop the information being spread through the industry and being put into practice by those who are more interested by the practical results than any endorsement by academic experts.
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  37. A brief explanation of the CO2 fertiliser effect from a Forester

    (I harvest my crop in 30 years so I have to know this stuff - and thanks for the comments because one never knows it all!)

    Plants combine carbon, water and sunlight to produce carbohydrate. That, along with a few minerals and trace elements is what is in your breakfast bowl, in your lunch box and will be on your dinner plate tonight. The CO2 fertiliser effect occurs where an increase in atmospheric CO2 concentration leads to an increase in plant production like adding dynamic lifter or super phosphate does. This is a good thing, right?

    Yes, it is a good thing, but it doesn't work well in reality. Plant production is ultimately limited by the "most limiting factor". This might be phosphorus, so adding super phosphate will give a boost to growth. If there is not enough nitrogen however, the plant can not use the added phosphorus, and adding the fertiliser is a waste of money. This is why farmers spend money analysing their soils. And what if water is the most limiting factor? You can fertilise all you want and get nothing in return.

    The majority of Australia's soils are nutrient poor, and receive limited rainfall, so guess what?

    Increased CO2 levels do have an important effect however, and there are indications that it is already happening. Plants open their stomata to breathe in CO2, and loose water in the process (stomata are the microscopic pores on leaves, and are a bit like a cross between sweat glands and lungs). If there is more CO2 in the air, plants don't have to open their stomata so much to get it, and loose less water. This means that they don't need as much water, which is lucky because over the last few years in Australia they mostly didn't get it.

    So what does this mean for climate change? Many places are expected to receive less rainfall over time, and plants need water to grow. An enhanced CO2 fertiliser effect seems likely to increase the water use efficiency and drought tolerance of many plants. Large scale Free to Air Carbon Enrichment experiments seem to indicate that original laboratory results are often not repeated in real world environments, and that what you see is what you get.

    But who is complaining. I think I will rather appreciate a bit extra drought tolerance in the future.
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  38. doug_bostrom at 12:17 PM, doug you should take the opportunity to check back from where you shop and see where it leads to.

    No, John, I want you to provide us with evidence for your assertion that grocery store shelves are replete with fruits and vegetables grown with enriched C02.

    Where's the data? You know your way around this stuff. What's the market penetration, in percentages?
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  39. By the way, John, I wasted a few minutes looking at Wittwer's "paper." It cites no references, none. The tract is riddled with political content, takes a wide excursion to discuss climate change, criticizes even Republican responses to the issue and claims that scientists "disagree on the likely effects of additional carbon dioxide on global temperature," carefully couched language indeed, technically true but conveying a powerful impression.

    It does contain the earliest occurrence of the term "alarmist" I've seen, dating back to 1992 as the item does.

    Is that where you're getting all this business about the life-giving properties of C02?
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  40. Re John Russel @ 35...

    Interesting about the greenhouses. So if we give them CO2 at night and stick a load of lights on, we could stress them out.

    A bit like human problems caused by changes in daylight, sleep and work patterns.
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  41. A relevant paper published in today's Nature [*]. This reiterates that any [CO2] effect requires enhanced N (nitrogen) nutrient as is well known, but the combined effects of [CO2]/N are likely to be counterproductive with respect to plant growth in natural ecosystems due to CO2/N-induced shifts in plant species.

    So natural ecosystems may respond poorly to enhanced [CO2] due to water and nutrient limitation and species shifts. In other words the terrestrial ecosystem is likely increasingly to falter as a sink to "mop up" large amounts of enhanced anthropogenic [CO2].

    Managed agricultural production will cope with enhanced [CO2] but is likely to become more expensive to support due to nutrient and water limitations.

    [*] J.A. Langley & J. P. Megonigal (2010) Ecosystem response to elevated CO2 levels limited by nitrogen-induced plant species shift Nature 466, 96–99
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  42. The link to the Climate Crock of the Week video doesn't work (for me, anyway).

    I'm guessing this might be what was intended:

    ... but perhaps there's a shorter way to link to it.
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  43. Mac at 21:51 PM on 1 July, 2010

    Mac that is a truly dismal, scientifically illiterate, and rather nasty site.... Do you really think that misrepresentation and ad hominem argumentation combined with poorly constructed sarcasm is a useful way of addressing scientific issues?

    BTW, I don't see where the "lost" "irony" applies to Mariana's article and comment. Can you please clarify
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  44. Looks like CO2 Generators are standard equipment indeed in commercial greenhouses. I don't know if it is good for plants or not, but there is a market for the gadget anyway.
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  45. @ #44
    Hey that is a compelling argument!

    Now that I think about it, my sister used to have a mosquito repellent machine in her mosquito infested backyard. It worked by pumping out a lot of CO2, which confused the heck out of the little buggers trying to chemotax to their next blood meal.

    Coming soon to a climate skeptic site near you: huge increases in CO2 will be a good thing, because it will cut down on mosquito bites and West Nile disease and malaria! (Or at least mitigate the increase in the geographical spread of those things due to increasing temperatures.)
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  46. Think I found the Climate Crock video here:
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  47. "Another effect of global climate change is erratic precipitation patterns"

    "balanced rainfall drastically reduced"

    Taking the first quote what do we have now, or what did we have 100 years ago? Non-erratic rainfall? Consistent rainfall? It's a blatantly obvious rainfall will be erratic in the future. It's always been erratic that's the nature of weather. There is no optimum, climate is chaotic whether it's under the influence of man-made or natural forces. You seem to fall into the trap that nature is in someway harmonious except when interferred with by man.

    These statements seem to wander away from science and dangerously close to the Gaia theory. Or an equally poor idea that man-made change is bad, presupposing that natural change is fine.

    "For one, the increased density of forest vegetation could increase the risk of wildfires, which have reared their ugly heads in California all too often in the past few years, wreaking devastating damage" PURE ALARMISM!! Suddenly dense forests are bad. Maybe we should chop them all down?

    In fact the whole thing wreaks of emotionalism rather than science, sorry.
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  48. This is an interesting read from the Journal of Experimental Botany (2009), mainly going on about the use of models (ooerr) but also giving a good round-up of current knowledge :

    Crops and climate change: progress, trends, and challenges
    in simulating impacts and informing adaptation
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  49. Marcus at 12:31 PM, most of the answers to your questions were in the Horsham FACE trial link I provided originally, but it required understanding the content, not merely the reading of it.

    1) does an enriched CO2 environment generate long-term, increased plant growth in the absence of ideal conditions?
    The only long term trial under such conditions has been over the last 100 years. Given the CO2 levels were stable for 1000's of years, a sudden 100 years of a constantly increasing CO2 levels indicates that at this stage, further increases in CO2 still accelerate the response with little indication of acclimation or any other adverse effects. Indeed some experts are crediting some of the huge leap in agriculture production over that time, in part to increased CO2 levels.
    2) does an enriched CO2 environment generate a significant increase in the quantity of *edible* biomass (usually seeds or fruit)?
    As indicated in the Horsham FACE trials, grain yields increased, significantly. The long established horticultural practice of CO2 enrichment in commercial greenhouse operations also support significant increases in edible biomass, why else would it have been done for so long?
    3) does an enriched CO2 environment generate a significant increase in the nitrogen content of the edible biomass?
    Don't get too hung up on this point. Grain protein levels and yield are often the inverse of each other. Some of the highest grain protein levels are found during the driest years when grain yields are down. Whilst the grain protein level was down slightly in the FACE trials, that was offset by a significant increase in grain yield which most importantly means that the amount of protein produced per hectare increased, and that is the most relevant factor in needing to produce enough food to feed the worlds population.

    4) does an enriched CO2 environment lead to a decrease in demand for other limiting factors (like fertilizer & water)?
    This is a really silly question. If plants are to grow bigger and better, for whatever reason, they require more nutrients, that is one of the most basic truths. If you want anything to increase growth, it requires extra inputs irrespective of what stimulates the extra growth. Do kids grow more if you feed them less? It appears however that water is utilised more efficiently when CO2 is the stimulating agent.

    5) does an enriched CO2 environment have any other positive or negative impacts on cropping *in the real world*?
    See (1) above. No-till farming and stubble retention has meant that it is now possible to produce viable crops in more marginal conditions. Increase plant efficiency in the utilisation of moisture is a further positive.
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  50. The Polish Institute of Environmental studies (2006):
    "Previously it was thought that increased CO2 concentrations deteriorate the quality of agricultural products [eg protein cereal - gluten], but accurate, many studies have not been found. Detailed studies have shown that the plants quickly, because within a few weeks acclimated to elevated carbon dioxide. " "... Photosynthesis, especially the most common type of C3 plants increases significantly with increasing concentrations of carbon dioxide (CO2). Simultaneously with the acceleration of photosynthesis, the optimum temperature shifts to higher temperatures. [...]"A particularly positive effect on the "fertilization" of CO2 [700 - 1500 ppmv] to react: "... plants growing in a greenhouse [which] at elevated carbon dioxide concentrations, it’s have higher yields on average by 33% ..."
    In addition, there is:
    - Reduction of stomatal conductance and transpiration increase efficiency of water use,
    - Reduce the amount of protein enzymes involved in carbon reduction cycle, which increases the efficiency of nutrients,
    - - Accelerate growth and increase the number of leaves and flowers,
    - Better regeneration of plants breeding - by tissue culture [in vitro],
    - In some cases reducing costs of light made [greenhouse] ... "

    CO2 is warming - the area of deserts and areas affected by natural disasters is to be increased, but ...
    "The prevailing view that the overall scale of expected changes involving global warming will bring positive effects in the rural economy. Indeed, if the sum of effective temperatures will increase it and increase yields of most crops - not only thermophilic. " Previous natural hunger, " ... were correlated with solar activity minima. The probability of randomness of this compound was calculated on an extremely small, ie the order of one ten-thousandth (King 1975). "
    Therefore, "... Always one of the best determinants of the old warm climates have been and are low prices for cereals and especially wheat. (quoted from above). "

    “Assessing the importance of expected climate change y its impact on world agriculture, we can conclude that growing anthropogenic global warming and, in particular, the increase in carbon dioxide concentration in the atmosphere can HAVE A FAVORABLE EFFECT on crop productivity in many regions of the earth. However, we should not forget that these estimates for DIFFERENT REGIONS COULD BE SIGNIFICANTLY DIFFERENT.” (The Close Relationship between Climate and the Global Food Problem, Budyko, 1998).

    "Old growth forests may actually still be accumulating carbon, in defiance of Odum's equilibrium hypothesis, explains Philippe Ciais, Deputy Director of LSCE, and co-author of the study. More than 30% of the planet's total forested area is unmanaged primary forest, half of which is located in temperate regions in the northern hemisphere. The database established for this study reveals that these ancient forests fix between 0.8 and 1.8 billion tonnes of carbon each year, and that 15% of the total forest area that has until now been totally IGNORED IN CARBON BALANCES is in fact responsible for at least 10% of all carbon sinking activity." (ScienceDaily, Sep. 14, 2008).
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