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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: mariana.ashley031@gmail.com.

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Comments 51 to 100 out of 104:

  1. Marcus at 12:14 PM. information from Monckton? ROTFLMAO. The only things that I know about Monckton is what I have read from his many fans on this site. Given the attention paid to him they obviously see him as being very influential.
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  2. HumanityRules, perhaps you should read some IPCC : 3.3 Changes in Surface Climate: Precipitation, Drought and Surface Hydrology How is Precipitation Changing? See also, for the UK : Changing intensity of rainfall over Britain
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  3. Wow, John, way to prove that you *didn't* read the results of that Horsham Trial too well. I read the results & understood them clearly-better than you did at any rate (apparently you can't even read a graph too well). I also paid close attention to the final comments that you also linked to. Looking at the graphs regarding GRAIN YIELD (not total biomass-that's completely different), we see in most varieties there is no significant increase in grain yield. In the remaining varieties, the increase in grain yield was significant but very small. By contrast, the decline in protein content-across the board-was significant, & not offset by the increase in grain yields in most cases. The experimental design included nothing simulating about hotter & drier conditions-they only compared rain-fed to irrigated systems, which is a far cry from simulating the conditions expected later this century if global warming gets worse. That you missed this PROVES you didn't bother to give this trial anything more than a casual glance, cherry-picking the bits you felt agreed with your viewpoint. The researchers admitted that, whilst protein levels in the grain decreased, the amount of nitrogen required was signficantly higher in the enriched CO2 conditions. Trust me, no farmer is going to choose to purchase even *more* expensive fertilizer to achieve little to no significant increase in grain yield. Other FACE trials from across the world show an equally disappointing increase in grain yields (5% to 8% maximum)-even in optimum conditions, & they have also noted a decrease in the *nutritional quality* of those seeds. That you haven't discovered that fact proves that you've clearly not looked too deeply into any FACE trials outside of the one in Horsham. Also, the great leaps forward in agricultural production have been as a result of increased use of pesticides, herbicides & fertilizers-& the move towards greater mechanization, not increases in CO2 in the atmosphere (which, need I remind you-yet again-is NOT the limiting factor in plant growth). It has, though, also made farming much more expensive-& marginal. Which is exactly why most farmers won't buy a significant increase in costs just to produce a very small increase in grain yield-at the cost of quality. At the end of the day, John D, you can keep repeating these falsehoods about the *wonders* of future CO2 increases, but repetition won't ever make it the truth! This tactic might work with all your denialist mates, but it doesn't cut the mustard around here. Now, go back & read the results of the FACE trial PROPERLY!
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  4. Here is part of an abstract which highlights that an enriched CO2 will lead to problems in photosynthesis & plant health in many cases: "Young bean plants (Phaseolus vulgaris L. cv Seafarer) grew faster in air enriched with CO2 (1200 microliters per liter) than in ambient CO2 (330 microliters per liter). However, by 7 days when increases in overall growth (dry weight, leaf area) were visible, there was a significant decline (about 25%) in the leaf mineral content (N, P, K, Ca, Mg) and a drop in the activity of two enzymes of carbon fixation, carbonic anhydrase and ribulose 1,5-bisphosphate (RuBP) carboxylase under high CO2." This does highlight that-even in the absence of the other detrimental impacts of CO2 enrichment-the significant increases achieved in *vegetative*-not SEED-biomass will most likely be increasingly short-lived as CO2 concentrations continue to rise, & will probably come at the price of overall plant health & nutritional value. This is something that the "CO2 is plant food" crowd never like to dwell on too much.
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  5. Thank you, HumanityRules (#47)! Those were two of the blunders in the post that I was about to comment on myself. The paragraph about rain also says: "With the global increase in temperature caused by the various factors affecting our climate's balance, increased evaporation means decreased soil moisture." So, if it is warmer, the soil is drier? In the Amazonas it is already warmer than in most places, but is it dry? The simple fact is that the earth has hot and dry places, hot and wet places, cold and dry places, and cold and wet places. Whether the ground is dry or humid depends on other factors than just the temperature. The paragraph about how more and denser forests and other vegetation would be a problem causing forest fires, is indeed preposterous. We know that on the shorelines and islands in and around the Mediterranean once were full of forests. When they cut down too many trees to build ships or make fire, the soil was washed down into the sea, and the last trees died. The soil is needed to keep the moisture in the ground, and together with the trees, they form the basis for more rain. Now we have dry macchia instead around most of the Mediterranean, which is really conducive to supporting forest fires. Would't it be better to have the forests back? No matter what grows in the soil, it is at least always better than barren ground.
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  6. What the science says: Journal of Experimental Botany Vol. 60, No. 10, pp. 2859–2876, 2009 doi:10.1093/jxb/erp096 Advance Access publication 28 April, 2009 REVIEW PAPER Elevated CO2 effects on plant carbon, nitrogen, and water relations: six important lessons from FACE Andrew D. B. Leakey, Elizabeth A. Ainsworth, Carl J. Bernacchi, Alistair Rogers, Stephen P. Long and Donald R. Ort
    1. carbon uptake is enhanced by elevated [CO2] despite acclimation of photosynthetic capacity
    2. photosynthetic nitrogen use efficiency increases at elevated [CO2]
    3. water use at both leaf and canopy scales declines at elevated [CO2]
    4. dark respiration is significantly stimulated in soybean leaves grown under elevated [CO2]
    5. stimulation of carbon uptake by elevated [CO2] in C4 plants is indirect and occurs only in situations of drought
    6. the [CO2] ‘fertilization’ effect in FACE studies on crop plants is less than expected
     Plant response is complex. Water and nitrogen use efficiency increases in general, C3 plants react better than C4 plants (the latter being an expensive adaptation to low CO2 levels), drought tolerance improves. Even crop yield increases pretty linearly up to about 500 [CO2] ppm and rate of increase only starts to decline above this level. In other worlds, yield is more or less proportional to the logarithm of carbon dioxide concentration (the same way CO2 forcing is said to be). SCIENCE VOL 312 30 JUNE 2006 Food for Thought: Lower-Than-Expected Crop Yield Stimulation with Rising CO2 Concentrations Stephen P. Long, Elizabeth A. Ainsworth, Andrew D. B. Leakey, Josef Nösberger, Donald R. Ort
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  7. It is a red herring and has no bearing on how much enhanced co2 levels are warming the earth, but dismissing the fertilization effect out of hand seems to me mistaken when it is still a matter of scientific debate,see the article linked to by chris @41. I saw a lecture by david archer where he suggests fertilization could explain the missing sink (more co2 is emitted by mankind than absobed by atmosphere and ocean) http://geoflop.uchicago.edu/forecast/docs/lectures.html BTW this is my 1st post though I've enjoyed reading your site for about a year and found it informative and scientific but, I'm sorry to say this article seemed much more(in tone) like an article on a"skeptical" site,and I hope this is just a typo " A rise in CO2 levels is not the only consequence of climate change"
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  8. I get a 404 error message when I click on the Climate Crock video link. Good post.
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  9. I really do not see the point of debating in circles about the "CO2 is plant food" meme. CO2 is, of course, a micro nutrient required for photosynthesis, no argument there. Plants have been doing well at relatively low concentrations of CO2 for over 800 000 years now. Whether or not doubling CO2 is going to help crops and forests is all rather irrelevant when sea level is going to rise by over 1.5 m, and when heat waves and drought are going to continue increasing in intensity and frequency in agricultural certain regions. There are other, much more relevant limiting factors on plant growth and yield, the permanent wilting point being one of them. The portions of the USA are currently experiencing a heat wave, and despite CO2 being at their highest levels in almost a million years, the high CO2 does not seem to be helping the plants much. As noted by Mariana, those arguing that CO2 is plant food relying on the fact the CO2 plant food argument "rests on a simple logical fallacy--the fallacy of exclusion". IMO, that is the end of the debate right there as it pertains to AGW. JohnD are you maintaining that we should double or more than double CO2 in the hopes that the alleged gains in crop yield will offset the myriad of negative impacts associated with a global warming of at least +2C occurring in an incredibly short time? That seems a rather poor reason/motivation to go on to more than double CO2.
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  10. HumanityRules at 23:25 PM on 1 July, 2010 Argus at 01:15 AM on 2 July, 2010 It takes a certain bravery to discuss second-order consequences of global warming like changing precipitation patterns and extremes, and wildfire prevalence and risk, since these can be easy to "pooh-pooh". I think Mariana’s analysis is a justifiable reflection of the scientific data. On precipitation patterns and extremes It is pretty clear that the predictions on changing precipitation paterns in a warming world are being borne out by real world observations [*]. Argus, you asked “In the Amazonas it is already warmer than in most places, but is it dry?”. The answer is that in Northern Amazonia, global warming has been accompanied by drying (reduced precipitation). The latitude band from around the equator to around 30 oN has become drier as the Earth has warmed during the 20th century, much as predicted. This latitudinal band of reduced precipitation will widen as the Earth continues to warm, and so Amazonia is expected to dry progressively towards the South as the Earth continues to warm. The higher latitudes (especially above 50o N and below 10 o) have seen enhanced precipitation. Global warming and shifts in precipitation regimes is expected (and already observed) to lead to amplification of extreme precipitation events [**] (one could cite more papers on this, but Allen et al. 2008 is a decent starting point). [*] X. Zhang et al. (2007) Detection of human influence on twentieth-century precipitation trends Nature 448, 461-465 abstract [**] RP Allen et al. (2008) Atmospheric warming and the amplification of precipitation extremes Science 321, 1481-1484 abstract On wildfire prevalence and risk Again real world observations support the expectation that global warming and shifts in precipitation patterns will (and are) lead(ing) to major changes in local hydrological cycles [***]. These effects lead to enhanced wildfire prevalence [****, *****] [***] e.g. TP Barnett et al (2008) Human-induced changes in the hydrology of the western United States Science 319, 1083-1086. abstract [****] AP Westerling et al (2006) Warming and earlier spring increase western US forest wildfire activity. Science 313, 940-943. abstract [*****] YQ Liu et al. (2009) Trends in global wildfire potential in a changing climate Forest Ecol. Management 259, 685-697 paper
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  11. Argus at 18:25 PM on 1 July, 2010 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" **************************************************************************************** I was not referring to the metabolism of the organism but to an appropriate description of what it consumes in terms of whether it's in a gaseous state or solid state. Since this post was written in reference to simplistic phrases used as propaganda for the masses, my idea was to find a simple counter phrase that could be used in rebuttal to members of the general public who say that "CO2 is plant food". The best one I can think of is the old phrase "Too much of a good thing is a bad thing". Examples: Too much food, for humans that is; too much oxygen in the atmosphere (double the % of Oxygen and you'll burn even the wettest jungle down). This response should come before the basic explanation as to what too much CO2 would do. The issue I'm trying to stress is not semantics, as was brought up by carrot eater #14, but the best response to people who simply do not understand the issue. Since they are being instructed (brainwashed) in what are essentially "memes", I am suggesting counter memes such as the previously mentioned one, "Too much of a good thing is a bad thing". As far as I'm concerned, the main issue is that of communicating with the Public and doing so at THEIR LEVEL. We cannot expect them to absorb even the simplest of explanations. To the extent that they may be able to, it would be necessary to use a label (the counter meme I suggested above) to make a simple rebuttal of ours more easily accessible to the overloaded "filing cabinets" of their minds. Our statements to the general public have to ALWAYS be understood in the context of the Denier propaganda they are susceptible to. The issue of communication to the Public is not merely about the LOGICAL but the PSYCHOLOGICAL. My apologies if I seem to be quibbling over an issue separate than those being discussed at the moment but I believe that communication with the manipulated Public, on their level, is of utmost importance.
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  12. doug_bostrom at 19:18 PM, you are starting to sound as if you think there is a conspiracy involved. However, do you accept that the practice of CO2 enrichment has been used commercially for decades and is as widespread as indicated in the article?
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  13. Why are you asking me about C02 enrichment, JohnD? You suggested I'd find my grocery store shelves richly supplied with fruits and vegetables grown using C02 enrichment but you cannot supply any data to support that claim. Don't ask me about enrichment, it's your impression you're trying to convey.
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  14. Marcus at 00:18 AM, if you read and understand the results so well, then perhaps you can explain what was the difference between the TOS1 and TOS2 trials, and what the results of each indicated. Only then will I be confident that you have read and understood the report. Can you also confirm whether the protein produced per unit area increased or not under the higher CO2.
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  15. Albatross at 02:33 AM, understanding the role CO2 plays in plant growth for food production is essential in order to obtain optimum growth. Optimum growth means greater efficiency in terms of nutrient usage, water usage and land usage. That has been proved by those commercial green house operators that adopted the practice long ago. As has always been the case, there are many different varieties of most plant species, and they all respond in different ways under different conditions. The trials being done under enriched CO2 levels are identifying ahead of time which varieties respond best allowing scientists to concentrate on further development on the desirable genetic makeups. What seems to be overlooked is that all plants are not going to be exposed to higher CO2 levels starting tomorrow, levels began rising over 100 years ago. Any negative aspects of higher levels of CO2 should be detectable now, but I don't see that being discussed. It seems that current ambient levels are considered optimum by some and that it will be all downhill from here on. Of course greater growth means increased inputs, it seems that it is only some posters here think otherwise. A backyard carrot grower might be able to continually grow carrots year after year without putting any nutrients back into the system and think he is getting something for nothing, but that is not the case with commercial growers.
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  16. johnd at 5:45 ""... CO2 enrichment has been used commercially for decades and is as widespread as indicated in the article" What article?
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  17. doug_bostrom at 05:51 AM, I wasn't asking you about CO2 enrichment, I was asking you if you know where the food you eat comes from. Most consumers are quite ignorant on the matter. In Australia labelling laws are being gradually tightened to keep consumers better informed, I don't know what the situation is in America. It may not be politically correct there to knowingly eat anything produced under enhanced CO2 conditions. It reminds me of the mad cow scare, how many USA consumers continued to eat meat rejected from export markets? Did they know it wasn't meeting export standards?
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  18. VoxRat at 06:25 AM , the article linked to in a previous post in my discussion with doug.
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  19. Ah - you mean that Wittwer article. I didn't find it terribly useful, in that it lacked any references. But I gather that greenhouse nurseries, have in fact, used CO2 enrichment to boost the production of certain plants. Which would make sense. However, extrapolating those results from the highly controlled artificial environment of a greenhouse nursery, where soil nutrients are not limiting and where competing plants (i.e. weeds) are not an issue, to farm and prairie land would be pretty naive. these guys for instance, found that though grass grew faster in increased CO2, the nutritional content (specifically nitrogen, i.e. protein) was degraded. And these guys (among others) say that increasing [CO2] may already be responsible for shrubland encroachment into pasture lands.
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  20. JohnD, you've made an assertion about how fruits and vegetables are cultivated and brought to table, namely that we may expect to see a plethora of mainstream foods in our markets that have been grown using C02 enrichment. So far you have done nothing to support that assertion with facts other than to cite a single opinion piece positing essentially the identical argument you're making and with no numerical information on how often consumers actually encounter products cultivated with C02 enrichment. Here's what you said: 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. You're attempting to convey an impression in support of your thesis that C02 enrichment is a great thing even when it's not being engineered and instead is out of control. In support of that you'd like us to believe that we're already benefiting in a significant way from C02 enriched cultivation. So far you have produced no data to support your assertion. At the end of the day folks have to be able to form an estimation of what is more or less useful information, or has any useful information content at all. You are casting an impression about what we might expect to find in our markets but so far you've not conveyed any actual information. Repair your problem by posting some numbers on market penetration of fruits and vegetables cultivated with C02 enrichment techniques.
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  21. Here is Fig. 2. from Long 2006. He goes for a hyperbolic fit, but it looks more like logarithmic (at least for realistic values of [CO2]), C4 plant response under normal (not drought) circumstances being a scaled down version of C3 plants'. In open air (FACE) the results are a bit more controversial.

    Fig. 2. Effects of elevated [CO2] on crop yield. Data are yields at elevated [CO2] relative to those at ambient [CO2] (arrow) for (A) soybeans in chambers (solid blue circles) and FACE (blue square, hidden behind red square) and wheat in chambers (red circles) and FACE (red square); and (B) C4 crops (maize and sorghum combined) in chambers (green circles) and FACE studies (green square). Error bars indicate mean ±90% confidence intervals around the means for the FACE studies. The chamber studies included 115 independent measures of soybeans (21), 211 of wheat (36), and 14 of maize and sorghum (table S3). These measures were divided into 10 classes of growth [CO2] in 100-ppm increments. Plotted values are the class means of growth [CO2] and yield. Solid lines are the least-squares fits for the nonrectangular hyperbolic response of yield to growth [CO2] from these enclosure studies of soybeans (blue line, r2 = 0.98), wheat (red line, r2 = 0.88), and C4 crops (green line, r2 = 0.99). The yield response of soybeans in chambers to growth [CO2] of 900 to 999 ppm [open blue circle in (A)] was an outlier and was excluded from the curve fitting. Full details of the meta-analysis methods and results from FACE are presented in the SOM and table S2.

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  22. VoxRat at 07:24 AM on 2 July, 2010 This exert is taken from your link. Critical matter for livestock and native prairie animals The scientists observed that doubling CO2 levels caused strong and consistent increases in grass growth which was due to improved water-use efficiency. Under the elevated CO2 levels, it was also found that plant nitrogen content was declining in native grasslands. This is a critical matter for livestock and for native animals that have grazed these prairies for thousands of years. Increased CO2 dilutes nitrogen concentration in grazing vegetation. Animals require sufficient forage protein nitrogen to sustain normal weight gains. N uptake is always a bit o a limiting factor in pastoral farming, generally with rye grass(perennial or annual) legumes are mixed in the sew. White clover normally, well because grasses dont fixate nitrogen. The majority o N is brought into the system via N fixation by legumes, with lightning storms pulling in 1-2%, and farmers top up with urea. There isnt enough info available to tell exactly what they were testing in that link, but it reads as though they are talking wild grasses. It would kinda be essential to know what the legume response is. What plant species are present? Clover will dump most of its N into the system during the Autumn die off. And it will be recycled through cattle waste and breakdown of organic matter... So short term studies have the potential for a bias,
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  23. I dislike the term "plant food" to describe CO2's role as the anabolic half of the respiratory cycle of life . It implies something that is required in traces like phosphorus or potassium rather than , along with H2O , the actual substance of plants , and therefore all life . Each of us , like every bite of food in the world , is over 90% CO2 combined with H2O by sunlight . That's why we animals on the catabolic , destructive , side of the cycle inhale O2 and exhale CO2 and H2O and defecate the rest . It's amusing to see to see Monckton named as source of this "meme" . I myself essentially learned it in grade school in the 1950s . Here's a great graphic :
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  24. "Also notable is that the temperature of Venus, commonly cited as what "runaway" warming could do to us, is twice as hot as the sun can possibly heat any object in its orbit. That is, Venus must have some internal source of heat because it is radiating much more energy than it is receiving from the sun." --Bob Armstrong
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  25. Bob Armstrong at 08:23 AM on 2 July, 2010 It's amusing to see to see Monckton named as source of this "meme" . I myself essentially learned it in grade school in the 1950s . ****************************************************************************************** It seems that I need to make a partial retraction of something that I've stated as well as an admission to a minor blunder. Concerning Lord Monckton being the first person to come up with the CO2="Plant Food" meme I specifically stated, "Lord Monckton is, as far as I know, . . ." It was a conditional statement since I knew better than to assume with absolute certainty, that my assumption was 100% correct. I appreciate the corrections pointed out to me. This is not a major point though since he is the one who testified to Representative John Shimkus, as Marian Ashley brought up in the third sentence of her post. Hence Lord Monckton, in essence, has popularized, in the recent past, this statement for his own purposes. As far as my blunder is concerned, I originally assumed, due to tiredness, that this was the same thread as the one immediately preceding it "What is Global Warming and the Greenhouse Effect?" That particular thread was, due to it's simplicity, geared towards explaining the basics to the Public in general. So were my statements on this thread which emphasized simple communication with the Public. Communication with the Public on basic issues is something we must stress or else we're preaching to the choir.
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  26. John D, I don't really feel that a change in Sowing Time is an accurate modeling of warmer temperatures in a 3-year trial. Indeed, I'm not entirely satisfied that the rainfed system accurately represents the drier conditions we have to look forward to. Perhaps over a 10-15 year period, but over 3 years, the inter-annual variability is just too high. For example, in Southern Australia, October, November & December of 2008 was exceptionally cold & wet by normal standards, yet November of 2009 was exceptionally *hot*! That said, the outcome of the trial was that only 2 out of the 8 varieties showed a significant increase in yield, under the optimum conditions. Protein levels were reduced in spite of an almost 25% increase in nitrogen uptake. The investigators also highlight a decline in mineral uptake & evidence of acclimation-hardly great news for the "CO2 is plant food" crowd. Unless you're suggesting the investigators themselves don't understand the results of their trial?
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  27. Another point, John D-here are the words of Dr. John Fitzgerald himself: "Results from the first three years of the experiment include increases in biomass, which in agriculture, translates into increases in yield and we’re seeing about a 20% increase in yield because of the elevated CO2. Now, the caveat there is that you can see increases in yield, but you also have to have sufficient water and nitrogen still to grow the crop and considering changes in climate, if this area of Australia, for example, has decreases in rainfall then we may not see the responses to be quite that dramatic in the future" & this: "Now, other results that are important to the agricultural industry is that we see a decrease in the plant nitrogen content. Now, nitrogen is a fertiliser, it’s what causes the green part of the plants to be green and that’s important…what happens is that translates into less nitrogen in the grain, which is less protein. So that interacts directly with quality issues and the wheat industry would be quite interested in understanding that. So, the nitrogen content, the protein content goes down and we’re seeing that very consistently. However, what’s interesting is that the total nitrogen extracted from the soil increases and that’s because there’s more biomass. So it’s just pulling a lot more nitrogen and that has potential impacts to future farming in terms of fertiliser requirements." When you also add in others factors which may well accompany a warmer world-such as increased incidence of plant pathogens & weeds-& we see the story behind the "CO2 is plant food" meme is not as simple, or as positive, as people like yourself would have us believe. Like I said elsewhere, other FACE studies are showing yield increases of little more than 8% in wheat (and only 6% in rice), & a consistent decline in the nutritional value of the rice & wheat-even without other impacts of global warming being considered. So, in fact, I'd suggest that all of my previous questions remain unanswered or-if they are answered-confirm my initial suspicions-which is that the claim that "CO2 is a plant food" is grossly over-simplistic when you consider the real world. Having contact with farmers in THE REAL WORLD also helps to confirm these suspicions.
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  28. @Marcus I. At the rainfall (restricting the use of CO2) - IV Report says: there is strict correspondance in warming, but the number of dry areas increases. For example, particularly South Africa today has to suffer drought. But ... Drought, climate change and vegetation response in the succulent karoo, South Africa, Hoffman, 2009: “Because drought has significant ecological and socio-economic impacts, investigations into its causes, consequences and mitigation have been regularly undertaken in South Africa over the last 100 years. Recent climate change scenarios suggest that there will be an increase in the frequency of extreme events, including drought, particularly in the winter-rainfall region of southern Africa as a result of the predicted pole-ward retreat of rain-bearing frontal systems.” “Our analysis finds no evidence for a decreasing trend in annual rainfall from 1900–2000 for the six rainfall stations investigated, and except for Springbok, there was no increase in the incidence of drought over the 20th century. Our analysis is in agreement with Warburton and Schulze8 who also report no decrease in annual rainfall for the winter-rainfall region in the latter part of 20th century. In fact, they suggest that relative to the period 1950–1969, the winter-rainfall region experienced an increase [?!] in rainfall from 1980–1999. [...]” Thus, the Fourth Report - even describing the twentieth century - is untrue. The forecasts contained therein are very uncertain - precipitation - variability is here non-linear. II. “The second question which arises from the climate change scenarios is concerned with the response of vegetation to drought. [...]” III. Pests. In my country, farmers are afraid that a new thermophilic pests attack maize. It is the object of my work (response to climate change). Note. Even professionals often forget that in countries where these pests are already, the yields and profitability of maize production are higher than ours ... It is also worth knowing that severe pest outbreaks occur in 1-3 years after severe winters. Why? - First frosts kill overwintering individuals dominated by diseases and parasites ... IV. Protein - nitrogen - the latest research on this issue are so short (time, replication), full of “artefacts”, that these affirmative: CO2 “harms” - never and should never be published. At most, as preliminary - without further, generalizing conclusions.
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  29. John, should this post be a response to “CO2 is plant food”?
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    Response: I like the rebuttals to be more referenced with links to peer-reviewed sources. I'll get to that when I get the time.
  30. Marcus at 12:20 PM, the scientists conducting the trial obviously felt it was about the only way to emulate drier conditions. In addition annual rainfall has been generally below average for the region in recent years. The area is also considered a low yielding region, so all these factors are working towards making the trial a realistic representation of forecast conditions. Whilst the grain protein level did fall, it has to be put into perspective. The higher grain yield meant that per unit area the amount of protein produced increased. Ask yourself which is better, producing 2.68t/ha @13.8% protein, or 3.23t/ha @13.25% protein?
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  31. There's a very interesting ABC 'Catalyst' documentary about the effects of raised CO2 concentrations on plant growth viewable here. Quote: "As carbon dioxide levels increase in the atmosphere some of our food crops will respond by becoming less nutritious and produce more toxins." It includes comments from several scientists working close to this issue. Well worth watching.
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  32. The U.S. Global Change Research Program don't seem as relaxed or engaged in wishful thinking as some of the so-called skeptics : Many crops show positive responses to elevated carbon dioxide and lower levels of warming, but higher levels of warming often negatively affect growth and yields. Extreme events such as heavy downpours and droughts are likely to reduce crop yields because excesses or deficits of water have negative impacts on plant growth. Forage quality in pastures and rangelands generally declines with increasing carbon dioxide concentration because of the effects on plant nitrogen and protein content, reducing the land’s ability to supply adequate livestock feed. Increased heat, disease, and weather extremes are likely to reduce livestock productivity. Now, either they are just a part of the big conspiracy or they don't know as much as some people posting on here. Or is it both ?
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  33. John Russell at 00:05 AM, as long as the transcript is a true reflection of the interviews, it seems that the focus was on what happens to the leaves of the plants rather than the grain or fruit that is normally eaten. These are all the examples mentioned, the only exception was when cassava was mentioned, and some of that is totally misleading which I refer to after these examples:- Dr Ros Gleadow Leaves of plants grown at elevated carbon dioxide have a lot less protein wheat, barley, rice, all of those in probably only 50 to 60 years time will have 15 to 20% less protein in them than they do now. ...... Dr Ros Gleadow In about 50 years time or even 100 years time eucalyptus leaves will have trouble supporting arboreal herbivores like koalas because the phenolic concentration will be too high and the protein level too low. ........ Emeritus Prof. Howard Bradbury If an insect comes and eats the leaf then it immediately gets a nasty taste of bitter hydrogen cyanide so it goes somewhere else. So this is a really great mechanism for protecting the plant. And there's about 2,000 plants that use this mechanism including apples, apricots, peaches. ........ Dr Graham Phillips This is a cassava plant. It is a small one the big ones can get up to 3 metres. Now the leaves can be eaten. They can be thrown into a salad as greens but the most important part of the plant as far as food goes is the root. Now that could be pealed chopped up and cooked. It could be turned into flour or indeed tapioca. Now the reason cassava is so popular around the world is the plant is highly drought tolerant. It requires very little water and can grow in extremely poor soils. ..... The misleading part is this:- NARRATION Before rising carbon dioxide and toxicity levels had been linked, Howard had been spending his retirement coming up with a simple method to remove cyanide from cassava. Emeritus Prof. Howard Bradbury 2004 I worked out the method and here it is 2010 and its not being used anywhere hardly except the Mozambique health department has finally said yeah that's a good method. They're finally adopting it, it's taken them 5 years! The method he claims as his own discovery is basically the traditional method of preparing cassava and has been used wherever cassava has been eaten for as far back as history allows it to be traced. I am amazed that he would lay claim to something that has been part of traditional life for so long. Like the Australian aboriginals have done, any society has, if finding any readily available foods toxic, devise simple methods how to render them safe, or ignore them as a source of food. Our modern day society is no different, but I've never before heard of any expert claiming credit for something that has been such a long established practice. Perhaps new techniques are developed, but the processing of cassava as described in the transcript is not a new technique, far from it.
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  34. doug_bostrom (#74), You love to chide me for being "off subject" but this time you are the offender! The climate of Venus is a fascinating subject, so I hope you know that Bob Armstrong's claim that the high surface temperature on that planet requires an internal heat source is nonsense.
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  35. I believe Armstrong's remarks about Venus are germane to any other claims he may make, GC. Short of some other form of external review, we have to use whatever cues are available, even if those come from the claimant himself.
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  36. Using this line of simplified reasoning means that I only need to eat a high protein supplement in order to look like Arnold Schwarzenegger :-) So here are the facts about CO2 and plants: 1) It is true that the amount of pollen released by a plant is proportional to the level of CO2 so you would expect many more plants. But the "keeling curve" continues to increase so why aren't the plants compensating? 2) In controlled experiments, a huge increase in CO2 will only increase the growth speed, size, and numbers of plants by a few percent because plant growth is limited by a lack of nitrogen (protein synthesis is impossible without it). Ammonium Nitrate is more important to plant growth than increased levels of CO2. (as an aside, even if plants did better in controlled experiments they would still have problems in the real world. Why? Plants are on the ground but CO2 is distributed throughout a three-dimensional volume. It's an area vs. volume issue) 3) plants pull in CO2 through a hole known as a stoma (or stomata). Since these pores also are also the site for water loss, a plant growing in a high CO2 environment will actually adapt to produce much fewer stomas TO LIMIT WATER LOSS.
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  37. There's evidence that increased CO2 also increases cold injury to plants (although diehard sceptics will say "but there's not supposed to be any more frost under AGW - sheesh !) Also will increased CO2 preference C3 native woody shrub growth in savanna grasslands (C4s)- so biasing grasslands into woody thickets such as happens in Australia, southern USA and southern Africa. Of course much of contemporary thickening is probably due to fire suppression but CO2 can increase the trend further. Examples of shrub invasion in Australia would be the huge woody weeds patch around Cobar. http://theland.farmonline.com.au/news/nationalrural/agribusiness-and-general/general/woody-weeds-love-co2/1729857.aspx?storypage=0 The ecophysiological effect on grasslands will be complex. On the plus side perhaps more freshwater runoff through improved transpiration efficiency although the following paper is somewhat controversial. http://www.nature.com/nature/journal/v439/n7078/full/nature04504.html http://www.nature.com/nature/journal/v448/n7157/abs/nature06045.html
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  38. LukeW at 00:04 AM, thanks for posting the link to the "The Land" article. Although it only gave a glancing reference to the role management may be playing in the increase of woody weeds, I think that management is probably a major factor. In recent years there has been a dramatic decline in stock numbers, particularly in those areas where the woody weeds are growing. Without the grazing pressure, the weeds will increase with or without increased CO2. This is one of the arguments put forward by the high country cattlemen who are being shut out of national parks by the government. All it will take is one devastating fire and the government will suddenly realise that the arguments that have been put to them make sense after all.
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  39. neilrieck at 23:28 PM, with regards to your point (2). Given this nutrient limitation is continually raised in discussions on this subject, it is an indication that there is little appreciation of how agriculture works in practice. The usual response is that the increased growth due to higher CO2 levels requires increased inputs of nutrients as if that is a negative factor, big enough to nullify all the benefits of the extra growth. That argument seems to imply that under current conditions the soil is able to provide an infinite supply of all the nutrients required, in the correct balance, completely free of charge. What is not understood so well is that the growing of food or fibre, with or without changes in CO2 levels, strips significant amounts of those essential nutrients from the soil which then disappears down the road on the back of a truck where it ends up being delivered onto someones plate, with half ending up being dumped. Increased output from the soil cannot be achieved without firstly replacing and then increasing those nutrients that are being stripped out. An equilibrium will be established based on what input is the limiting factor during the growth period. That may be the optimum growth achievable under those circumstances, but it may not be the optimum growth that the plant itself is genetically capable of. It has been over 100 years since it was discovered that one of the limitations to achieving optimum plant growth was the enhancement of the supply of CO2 to the plant, and trials since then have established that optimum plant growth for many species requires CO2 levels perhaps several times current levels. Obviously that extra growth requires extra inputs of all the other nutrients in order to provide the increased output. There should not be any concern or mystery about such a basic truth.
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  40. johnd at 11:35 I agree with you here john.... especially when you are talking N, it is meaningless to run short term trials on plant species that dont fixate N... Without knowing the legume response to raised co2 levels. Most farmers will be able to tell at a glance whether their crop/pasture is deficient in N P K or S. And take steps to adjust it. But from all the various links ive read here, plant uptake of N was increased, but growth outstripped available N... so the Q is, if the N was availabe, what would have the composition been? Also, livestock do fine of carbohydrate, dairy stock wont produce that well of it however... but it does depend exactly how starchy it is... but there are steps that can be taken to increase digestibility, from topping/wilting pasture pre grazing, to making silage.
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  41. doug_bostrom, (#85) Certainly Bob Armstrong's comments are germane. However, when he participates in discussions with folks like Chris Colose, DeWitt Payne and Leonard Weinstein, his arguments don't get much traction. When his hypothesis is challenged he tends to get testy. Take a look at him in action at the "Science of Doom" in the comments following this link: http://scienceofdoom.com/2010/06/12/venusian-mysteries/#comment-2953 Getting back to the theme of this thread, there is plenty of evidence to show that higher concentrations of CO2 increase the rate of plant growth if other essential nutrients are adequate. Even more convincing than academic studies such as FACE & EUROFACE is the fact that horticulturists using greenhouses routinely employ enhanced CO2 levels to improve productivity.
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  42. OK, a question from the peanut gallery here. Greenhouses add CO2 for increased plant production and growth - great, seems to work. However, according to John Russell and Advanced Greenhouses, the effective time for CO2 addition is during the day, when CO2 levels are decreased to 150-200 ppm. It sounds to me like the closed environs of a greenhouse prevent sufficient CO2 to reach the plants - they're starved during daylight hours. That won't happen in open air! So my question: If CO2 addition to greenhouses is to make up for closed air systems with insufficient (below ambient) CO2 levels, bringing the levels back up towards or past ambient, how is that an argument for CO2 enhancement in nature??? It sounds to me like evidence that plants do poorly at low CO2 levels, not that they be greatly enhanced with high CO2 levels. Given, of course, that they evolved at something close to current (or pre-industrial) ambient conditions. Comments, anyone? Are the greenhouse effects just a different category (i.e., not relevant) from the FACE tests?
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  43. Sorry - in the previous comment the CO2 levels without enhancement appear to hit 100-250 ppm, not 150-200. Typo on my part...
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  44. KR End of the day, we are carbon based life forms, the bottom of the food chain is photosynthesis... And co2, h20 and sunlight is where all life springs from(ohhh, and N is also pulled from the atmosphere by certain types of plants, also tied to their photosynthesis)... Not everything about co2 is bad. Increasing co2 will aid most plants in photosynthesis... potentially increasing the biosphere.... depending on climatic implications, its not a simple Q... but the short answer is, co2 is good for plants. I dont know at what exact level plants stop photosynthesizing, but id imagine, to much below 100ppm, life on this planet would be in serious trouble. Plant response to co2, and climatic responses to co2, are different issues in my opinion.
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  45. JohnD - as I said in my post. "Of course much of contemporary thickening is probably due to fire suppression but CO2 can increase the trend further." In Australia at least - the Kimberley, Top End, and Cape York probably burns too much and too hot, while our southern grasslands burn too infrequently. Many of savanna ecosystems have been described as "fire mediated sub-climax ecosystems" - i.e. increase the fire and reduce the grazing pressure - light by human hand or do not prevent natural fires - the balance is maintained - less natural woody shrubs and trees. Overgraze and prevent fires - little grass as fuel to burn - woodies get a foothold and more tree competition for water, nutrients and light means less grass growth and this feedback cycle "thickens" up the woody vegetation. Areas can go from open woodlands the veritable thickets in 30-50 years. The massive Cobar woody weeds region, the Pilliga forest, central Queensland woodland thickening, and SW Queensland Mulga forests being examples. Increased CO2 in the atmosphere will preference the C3 woodies even more. SO CO2 fertilisation isn't a totally positive one way street. Although the woodland thickening probably puts the northern Australian grazing industry into a net sink rather than source of emissions - albeit with reducing grazing potential from less grass area. The issue though is to get a map and see how much of the world are covered in savannas. How much will change with the combination of changes in fire regime and CO2? How many people depend on these ecosystems? http://www.nrel.colostate.edu/projects/srs/images/global_savanna_ecoregions_main_hr.png
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  46. johnd at 09:09 AM on 5 July, 2010 I posted this reply to JMurphy at 06:39 AM on the "An account of the Watts event in Perth". It refers to a matter discussed earlier on this thread, so perhaps should be responded to here. "The bottom line for grain yield in the FACE trial in question was this:- (1) 2.68t/ha @13.8% protein. (2) 3.23t/ha @13.25% protein. You tell me which result produces the highest overall nutritional value, and then explain whether that is a positive outcome or not"
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  47. LukeW at 22:47 PM, as well as the C3 woodies you mention, the following major grain crops also have some C3 species. Wheat (C3) Corn (Maize) (C4) Rice (C3) Barley (C3) Sorghum (C4) Oats (C3) Millet (C3 & C4; different species) Rye (C3) Triticale (wheat & rye hybrid; C3) The problem of encroachment onto grasslands will only occur if the grassland is not being grazed at all, or very lightly. It is almost impossible to establish any sort of plantation without excluding all forms of livestock. If encroachment onto grassland occurs, it indicates that the grassland is not being utilised. As is often said, it is not waste country, only country wasted.
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  48. JohnD - on the contrary - this is about woodland thickening more than shrub encroachment. Indeed the phenomenon is more likely to occur with heavier grazing and suppression of fire. Fire kills the natural woody shrubs or tree seedlings and keeps the savanna woodlands open. Heavy grazing removes grass fuel. Although many crop plants are C3s these areas are not suited as crop lands or plantation forestry. Rainfall to sporadic to semi-arid. They do however host large herds of domestic stock (Australia) or native herbivores (e.g. African plains).
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  49. As expected by many, in this case also there's not just CO2, other limiting factors may come into play. And they may depend on the particular specie under study. A new study published in Nature (Langley et al. 2010, paywalled) shows a CO2 fertilization effect on C3 sedge and C4 grasses only in the first year. Supplying N together with CO2 "strongly promotes the encroachment of C4 plant species that respond less strongly to elevated CO2 concentrations. Overall, we found that the observed shift in the plant community composition ultimately suppresses the CO2-stimulation of plant productivity by the third and fourth years." More generally, one may think that profound changes in the ecosystem might be produced by changing atmospheric (and/or soil) chemical composition. Adding changes in temperature and precipitations it's easy to envisage hard times ahead for the Earth System Models.
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  50. Riccardo at 22:54 PM, given that CO2 levels began rising over 100 years ago, and as well the introduction of legumes that fix nitrogen into the soil has become part of modern farming practices, if the finding of the study cited are valid, to what extent has the CO2 fertilisation effect been suppressed, and to what extent have C4 plant encroachment occurred in todays environment compared to that before CO2 levels began rising and the widespread introduction of legumes began?
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