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Plant food

The argument that carbon dioxide is plant food and that we should welcome increased concentrations of the stuff as leading to bumper crop yields is one that is not given much credence by the other side of the global warming debate. Perhaps they should think again, as this article, recently published in the Royal Society's Phil Trans B, suggests that there is much truth in it.

CO2 enrichment is likely to increase yields of most crops by approximately 13 per cent but leave yields of C4 crops unchanged. It will tend to reduce water consumption by all crops, but this effect will be approximately cancelled out by the effect of the increased temperature on evaporation rates. In many places increased temperature will provide opportunities to manipulate agronomy to improve crop performance. Ozone concentration increases will decrease yields by 5 per cent or more.

Plant breeders will probably be able to increase yields considerably in the CO2-enriched environment of the future, and most weeds and airborne pests and diseases should remain controllable, so long as policy changes do not remove too many types of crop-protection chemicals. However, soil-borne pathogens are likely to be an increasing problem when warmer weather will increase their multiplication rates; control is likely to need a transgenic approach to breeding for resistance. There is a large gap between achievable yields and those delivered by farmers, even in the most efficient agricultural systems. A gap is inevitable, but there are large differences between farmers, even between those who have used the same resources. If this gap is closed and accompanied by improvements in potential yields then there is a good prospect that crop production will increase by approximately 50 per cent or more by 2050 without extra land. However, the demands for land to produce bio-energy have not been factored into these calculations.

You could almost get the impression that the biggest threat to the food supply is coming from government.


(H/T Roddy Campbell)

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Reader Comments (54)

CO2 is part of the food chain and energy is a major component of what you eat today. For example, corn yield in the USA averages about 165 bushels/acre today. It has increased an average of 1.8 to 2.0 bushels per acre since 1940. Do the math to see how much the paltry harvests of 1940 where and how many that would feed. There are reasons. Take corn for example.

Everything from the huge tires that hit the ground, to the drills that plant the seed to the herbicides that kill nutrient robbing weeds eliminating the need to cultivate to the fertilizers needed to grow the plant and ending up with the combines that harvest the ears require energy, and energy, and energy. The cheaper energy the more food. Even the increase in CO2 produced by the use of all that energy is something corn absolutely needs.

If you restrict energy, regardless of how or why, and CO2 you will directly impact, negatively, your food supply. Being skinny is one thing but if one disrupts the energy supply you will, in fact, see the return of Biblical type famines

Aug 17, 2010 at 11:24 AM | Unregistered Commentercedarhill

This was one article from a whole crop published simultaneously by the RS, all on food security in 2050.

Aug 17, 2010 at 11:35 AM | Unregistered CommenterRoddy Campbell

It's not hard to work out the effect of higher temperatures.

Simply visit a bunch of places that have higher temperatures, and also a bunch of places that have higher humidity and/or higher evaporation rates.

Avoiding my domicile (Australia) It seems that higher temperatures correlate well with higher rainfall, higher productivity and/or lower evaporation.

If the present tropical countries are en example then soil pathogens don't affect a year-on-year increase in productivity - cf the fake BBC decline in yields rather than the actual growth in yields

Aug 17, 2010 at 11:55 AM | Unregistered CommenterJerry

Modern greenhouses are computer controlled and they enrich the house routinely to I think about 1400 ppm to increase yields. The RH is also managed as is the temperature.

This is what I was initially confused about ! If we increase the atmospheric CO2 isn't this good?

Don't people already know this is occurring everyday ?

Aug 17, 2010 at 12:02 PM | Unregistered Commenterconfused

Yes, the real problem could be EU restrictions on pesticides/herbicides and ridiculous bio-fuel policies. Technologies bring advances and politicians bring retrogressions

Aug 17, 2010 at 12:07 PM | Unregistered CommenterPhillip Bratby

I can't see such an, ahem, obviously shoddy, ahem, piece of work making it into AR5, can anyone else? It's almost as bad as that MMH10 paper! Let alone McShane and Wyner 2010! And deniers claim they can't get published, pshaw!

Unfortunately there's still little sign of our lords and masters in government or (more importantly) the EU waking up and smelling the coffee. If only we could be Pam Ewing in the shower.

Aug 17, 2010 at 12:38 PM | Unregistered CommenterPeter Dunford

I used to work in CO2-enriched glasshouses that were (and are) routinely run at around 1200ppm. Curiously, one of the difficulties for the operators is the production of clean CO2 for this enrichment, especially if the source of heat is not a local boiler installation.

My former employers have this problem, as they are exploring geothermal heating, whose economies are somewhat offset by the need to purchase tanks of CO2!

Aug 17, 2010 at 1:26 PM | Unregistered CommenterJames P

Out of curiosity, does anyone know why ozone has a negative effect on yields? A quick Google sent me to , which was altogether unsatisfactory for explanation.

Aug 17, 2010 at 1:27 PM | Unregistered CommenterHaroldW

"Pam Ewing in the shower"

Now you've spoiled my concentration...

Aug 17, 2010 at 1:29 PM | Unregistered CommenterJames P

I specifically wrote about the benefits to plants/trees and crop production from increasing CO2 in one of my responses to the EPA's endangerment publication. There are many articles in the literature about increased yields resulting from elevated CO2, often accompanied by lower demands for water; there is even a book. There is also a NASA satellite study demonstrating the greening of the Earth over time. Needless to say, the EPA ignored me.
However, just imagine what will happen as the Earth begins to fall into the next ice age. In a short time frame, major food exporters such as Canada will be converted into food importers as the northern regions will be unable to grow crops.

Aug 17, 2010 at 1:34 PM | Unregistered CommenterDrCrinum

Dr Crinum
As you say, enhanced CO2 crop yield has an extensive and uncontroversial experimental basis in the literature, which is clearly off-message and thus suppressed.

Also, the severity of natural processes is also suppressed by restricting climate debate to the rather trivial (in comparison) climatic variations in the current Holocene interglacial.

This summary webpage, from some obscure anonymous author, does have very revealing longer timescale temperature curves and demonstrates that the main risk for the destiny of humanity has always been and will remain severe cooling.

By suppressing the ice age question and its causal natural drive mechanisms in order to promote a warming propaganda campaign, current climate science could be accused of ethical mischief verging on moral bankruptcy.

Aug 17, 2010 at 2:16 PM | Unregistered CommenterPharos

It is not hard to understand that increasing CO2 should improve crop yields since we are only about 150ppm above the lowest level needed to support plant life.

Aug 17, 2010 at 2:45 PM | Unregistered CommenterDung

Reducing carbon emissions is extremely bad for the future of food supplies. With an increasing world population, agriculture needs as much atmospheric CO2 that it can get, and increasing CO2 has many, many beneficial effects. In fact, the present level of CO2 is just above the suffocation level for plants using the C3 photosynthetic pathway, which constitute most of the important crops for human consumption. These crops are severely held back in their growth: given sufficient light, warmth, moisture and nutrients, the present level of CO2 is the limiting factor, which is why glasshouses routinely enhance the CO2 levels to give crops the chance to flourish to their natural potential.

The phrase "It will tend to reduce water consumption by all crops, but this effect will be approximately cancelled out by the effect of the increased temperature on evaporation rates" assumes a link between CO2 and temperature increases, and fails to consider precipitation. All other things being equal, increasing CO2 WILL decrease water consumption. The benefits can only be 'cancelled out' if CO2 also causes significant increases in evaporation WITHOUT A CORRESPONDING INCREASE IN RAINFALL, i.e. there is less water around for the plant to use, and the region becomes more arid. But if the premise that 'CO2 increases result in increased evaporation' is true, it is also true by the same argument that increased evaporation from the oceans (which is a far greater surface area than land) will result in higher levels of rainfall (all the models show this), and where agriculture is rain-fed there will generally NOT be a reduction in water availability. In regions that are not arid (not water limited), the argument about increased evaporation is a red herring, and in arid regions where water availability is currently a limiting factor, increasing CO2 reduces plant water stress. Increasing CO2 is a positive benefit in both arid and non-arid regions, and will bring land which is currently too arid to support crops into use.

See a number of my posts for more on this:

Aug 17, 2010 at 2:55 PM | Unregistered CommenterScientistForTruth

Harold W "Out of curiosity, does anyone know why ozone has a negative effect on yields?"

Ozone is a plant poison: it interferes with the production of rubisco, essential for photosynthesis. Plants also react to ozone (and some other poisons) by closing their stomata to inhibit uptake of ozone, but this also blocks uptake of CO2, shutting down photosynthesis.

The good news is that where there is a somewhat higher level of CO2 plants are more tolerant of ozone - because they can still get decent levels of CO2 into the leaves with partly closed stomata. In fact, with higher levels of CO2, plants are more tolerant of practically everything: heat stress, water stress, cold stress, salinity, pollution etc. Not surprising really - life forms are a lot more resistant to stress when they are not also suffocating.

Aug 17, 2010 at 3:09 PM | Unregistered CommenterScientistForTruth

I have just checked the various papers in the Trans, Roy Soc. special issue on Food, thanks for the link, Bish. But apart from natural pique that my own paper on all that in Energy & Environment (2009) is studiously ignored, equally I cannot help but note that while Jaggard et al correctly allow for the role of rising atmospheric CO2 in raising yields of food crops more than pari passu with population growth by 2050, they totally ignore the likely impact of success of the IPCC-COP15 gang in reducing CO2 emissions to only 40% of their level in 2000. Inverting their projections, mass starvation will be the only outcome of COP15 is they do so succeed during their vacation in Mexico just 4 months from now.

Aug 17, 2010 at 3:32 PM | Unregistered CommenterTim Curtin

One wonders how the Royal Society will square their belief that CO2 is a menace with their own published evidence to the contrary...

Aug 17, 2010 at 3:41 PM | Unregistered CommenterJames P

Out of curiosity, I looked up the effects of CO2 on humans. Since we are at .3 to .4% in the normal air outside, we do have a way to go before it reaches 1%, which is where you start to see effects on humans.

While many poo-poo Wikipedia, they do have an easy to see and read chart of the effects of CO2 on us, HERE

Aug 17, 2010 at 3:58 PM | Unregistered CommenterDon Pablo de la Sierra

Don Pablo, those decimal points are very slippy, especially when so many zeros are present. 380 ppm is 380 out of 1,000,000 which expressed as a percentage is 0.038%

Aug 17, 2010 at 4:06 PM | Unregistered CommenterCumbrian Lad

In my frequent bouts of shouting at the (BBC) radio, I tell the interviewer to ask the warmist (it always is) what the proportion of CO2 in the atmosphere is. It seems simple enough, and would not only establish whether he was worth continuing to interview, but, if he actually knew the answer, would remind the listeners how low the number really is.

One molecule in every 2600 doesn’t sound very threatening, somehow.

Aug 17, 2010 at 4:59 PM | Unregistered CommenterJames P

One of my little foibles when in a conversation on a broadly GW issue is to ask people what they think the percentage of CO2 in the atmosphere actually is. Estimates usually range from 1% to around 20%, and these are not usually unintelligent people. Their reaction when the 0.038% figure is produced (with a flourish of course!) is surprise followed by thoughtfulness.

Aug 17, 2010 at 5:05 PM | Unregistered CommenterCumbrian Lad

Cumbrian Lad

Miss placed my new glasses and so had to use my old ones. You are quite correct. Thank you for being so polite about it :)

Aug 17, 2010 at 5:42 PM | Unregistered CommenterDon Pablo de la Sierra

The idea, in the quote included by Your Grace in this post, that the reduction of water needs in C4 crops will be somehow offset by increases in evaporation due to warming, is wrong. Evaporation from plants (evapotranspiration is its name) is included in the water needs of the plant. What increased CO2 does is reducing the total requirement of water by a plant.

Global warming, on the other hand, will not bring drought but higher evaporation from the sea and other water bodies, increased clouds, and increased precipitation at a global level. However, due to local effects (winds, oceanic currents and the like) some regions may experience a decrease in precipitation. For instance the North of Mexico and neighboring US states, all growin maize (a C4 crop) will probably experience (the IPCC forecasts) a reduction in precipitation over this century. This would reduce water availability for maize, but the increased CO2 concentration accompanying GW will at the same time reduce the requirement of water in maize. The overall net effect on maize would be beneficial, except of course if the reduction in the supply of water is too large, but nobody is envisaging that (least so the 2007 IPCC report). Studies by several authors such as Gunther Fischer, Petra Doll and others show that the direct and large effect on photosynthesis and yields in C3 crops, the lesser similar effect on C4 crops, and the economization of water in C4, will cause an overall benefit to crops. On the other hand, the effect of climate change on agriculture should include endogenous changes (by farmers) in cultivation techniques, water management, crop mix, choice of crop varieties and the like, because all agriculture is the result of an interaction between Man and Nature, in which Man adapts its agricultural activity to the (ever changing) local climate. Current serious evaluations of the impact of GW on food indicate that food production and consumption per capita by 2100 will be much higher than today, that the prevalence of undernourishment (too little food) will be reduced to nonsignificant levels even in the worst-case scenarios, and that the net likely effect of climate change on those prospects is very small, probably positive although in some studies (and at certain zones of the world) the small effect may be negative, without altering much the general conclusion in either case. These conclusions are reached without questioning the climate change predictions in the 2007 IPCC report, and using up-to-date assessments published at the best journals. Incorporating a modicum of existing criticism of IPCC forecasts might greatly enhance the positiveness of the conclusions.
For the case of Latin America, and also for reasons of general theoretical and methodological discussion, I dare suggest my own recent book-sized work (co-authored with my son Emiliano), now on its way to publication, on climate change, agriculture and food security in Latin America and the Caribbean (a preliminary version is at

Aug 17, 2010 at 6:06 PM | Unregistered CommenterHector M.

Cumbrian Lad

What figures have you read relating to what percentage af total emissions of CO2 inro the atmosphere are due to human activity?
I have read various estimates, all between 5% and 10%.
This makes the claim that CO2 in the atmposphere has increased by 35% largly due to man, somewhat hard to swallow?

Aug 17, 2010 at 6:16 PM | Unregistered CommenterDung

ERRATUM: My mention of Fischer and Doll in my previous comments refers to assessments of how GW will affect water availability and water use in world agriculture. On the particular issue of the effect of atmospheric CO2 on crops (either C3 and C4) there are still debates, especially because current methods (FACE or others) need improvement. Ainsworth et al 2008 (see below) call for methodological improvements and a new generation of studies. Some key references:

Long, S.P., Ainsworth, E.A., Leakey, A.D.B., Nosberger, J., Ort, D.R., 2006. Food for thought: lower-than-expected crop yield stimulation with rising CO2 concentrations. Science 312, 1918–1921.

Tubiello, Francesco N., Jeffrey S. Amthor, Kenneth J. Boote, Marcello Donatelli, William Easterling, Gunther Fischer, Roger M. Gifford, Mark Howden, John Reilly, & Cynthia Rosenzweig, 2007. Crop response to elevated CO2 and world food supply (A comment on “Food for thought” by Long et al., 2006, Science 312: 1918–21.). European Journal of Agronomy 26: 215–223.

Schmidhuber J. & F. N. Tubiello, 2007. Global food security under climate change. Proceedings of the NationalAcademy of Sciences of the United States of America 104:19703–19708.

Tubiello, F.N. & F.Ewert, 2002. Modeling the effects of elevated CO2 on crop growth and yield: a review, European Journal of Agronomy 18 (1-2):57-74. Doi:10.1016/S1161-0301(02)00097-7.

Tubiello, F.N., C. Rosenzweig, R.A. Goldberg, S. Jagtap, & J.W. Jones. 2002. Effects of Climate Change on US Crop Production: Simulation Results Using Two Different GCM Scenarios. Part I: Wheat, Potato, Maize, and Citrus. Climate Research 20 (April): 259–270.
Leakey, Andrew D.B., 2009. Rising atmospheric carbon dioxide concentration and the future of C4 crops for food and fuel. Proceedings of the Royal Society – B: Biological Sciences 276:2333-2343.

Ainsworth, E.A., Long, S.P., 2005. What have we learned from 15 years of
free-air CO2 enrichment (FACE)? A meta-analysis of the responses of photosynthesis,
canopy properties and plant production to rising CO2. New Phytol. 165, 351–372.

Ainsworth, Elizabeth A., Claus Beier, Carlo Calfapietra, Reinhart Ceuleman, Mylene Durand-Tardif, Graham D. Farquhar, Douglas L. Godbold, George R. Hendrey, Thomas Hickler, Jörg Kaduk, David F. Karnosky, Bruce A. Kimball, Christian Körner, Maarten Koornneef, Tanguy Lafarge, Andrew D.B. Leakey, Keith F. Lewin, Stephen P. Long, Remy Manderscheid, David L. McNeil, Timothy A. Mies, Franco Miglietta, Jack A. Morgan, John Nagy, Richard J. Norby, Robert M. Norton, Kevin E. Percy, Alistair Rogers, Jean-Francois Soussana, Mark Stitt, Hans-Joachim Weigel & Jeffrey W. White, 2008. Next generation of elevated [CO2] experiments with crops: a critical investment for feeding the future world. Plant, Cell and Environment 31: 1317–1324.

Lobell, D.B. & C.B. Field, 2008. Estimation of the carbon dioxide (CO2) fertilization effect using growth rate anomalies of CO2 and crop yields since 1961. Global Change Biology (2008) 14, 39–45,

Also see references and comments in the IPCC WG2 2007 report, ch.5, p.276 and 282, and in my draft book cited in previous comment, section 4.6.
Note that two main methods are currently applied to forecast impact of GW on agriculture: Ricardian models and Integrated Assessment models. The former do not account for CO2 effects, whilst most of the latter do.

Aug 17, 2010 at 7:10 PM | Unregistered CommenterHector M.

"You could almost get the impression that the biggest threat to the food supply is coming from government."

LOL, you think pretending to try to reduce CO2 emissions has an effect on the food supply?

Seriously though, biofuels are probably worse.

Aug 17, 2010 at 7:54 PM | Unregistered CommenterDagfinn


Biofuels are down to government.

Aug 17, 2010 at 8:03 PM | Registered CommenterBishop Hill

Dung, not an easy question, and the numbers are subject to some discussion! I'm no expert on this, and estimates vary widely, but the figures that David Mackay uses in his monograph on energy seem reasonable (see and amount to around 3% of total emissions. However, this is only one side of the equation. Natural emission of CO2 by the biosphere and oceans is more or less balanced by natural absorption. This is why a larger part of the increase in the atmosphere is attributed to man. (About half of what we emit is absorbed by natural processes).

There was a lengthy article and discussion of the CO2 picture on WUWT just recently which would be worth a look.

Aug 17, 2010 at 8:15 PM | Unregistered CommenterCumbrian Lad

Don Pablo, you're most welcome. I'm conscious now that next time I hazard some figures I'll make a right horlicks of it, and you'll ever so kindly point out my errors :)

Aug 17, 2010 at 8:21 PM | Unregistered CommenterCumbrian Lad

One of the strongest objections made against AGW is that carbon dioxide is beneficial to all plant life. This is not true for 85% of plant life.
There are three kinds of photosynthesis, C3, C4 and CAM. C3 photosynthesis dominates the scene.  The greater part of photosynthetic plants belong to this group. Almost all trees -- tropical, deciduous and conifers -- are C3 plants. Our essential food plants are C3 — wheat, vegetables, legumes, fruits, etc.
C3 plants constitute 95% of all the plants in the world, including phytoplankton.
Grass, rice, sorghum and amaranth are mostly C4 plants. So what’s the problem? Well, the problem is that photosynthesis in C3 plants is inhibited when the carbon dioxide concentration is high in the atmosphere. C3 plants will succumb and wither in atmospheres of 0.1% carbon dioxide. This occurs because as the interstitial carbon dioxide in the leaves increases, photorespiration takes over from photosynthesis, which is an unproductive process in terms of carbon dioxide fixation, synthesis of food, the releasing of oxygen and the production of ATP; all these processes are inhibited when C3 plants are exposed to a level of 0.1% of carbon dioxide, as insolation and temperature increases above or below certain optimal parameters, or when the environmental humidity is low.

Pseudoscience shows its face on the other side of the debate with anti-AGW claims that a high concentration of carbon dioxide are beneficial for all plants. In reality that claim is simply not true. Actually, high levels of carbon dioxide would be beneficial only for about 100 plant species around the world, corn and sugarcane among them. For the remainder, carbon dioxide is not good; or perhaps I should have used the word “lethal”.

Aug 17, 2010 at 8:43 PM | Unregistered Commentertom

Tom, I think you have that backwards...

Aug 17, 2010 at 9:00 PM | Unregistered CommenterCumbrian Lad

As someone who grows vegetables in NE England, I have to report that crops have been anything but bumper this year. This seems to be due to the spring and early summer being very cold and very dry. Apples, pears and plums are doing well, carrotts cougettes and runner beans have been OK, everything else has been pretty poor. The important thing is not to read any significance whatsoever into this post, good years and bad years come and go, always have.

Aug 17, 2010 at 9:08 PM | Unregistered CommenterStonyground

tom I am no scientist but in this thread are first hand experiences of greenhouses raised to 1200 ppm of CO2 to increase yields (successfully).
Your 0.1% is about 1000 ppm mate?

Aug 17, 2010 at 9:53 PM | Unregistered CommenterDung

Tom, you are just SO wrong. Wrong on so many points. C3 photosynthesizers are no way harmed by CO2 at 0.1%. In fact, C4 photosynthesizers have little benefit from increased CO2, but C3 photosynthesizers continue to improve up to at least 0.1% CO2. The chances of getting to 0.1% in the atmosphere are pretty unlikely anyway from less than 0.04% currently. If we consider 500ppm, 600ppm, 700ppm we are seeing great improvements. I don't know where you are getting your information from about C3 plants withering and dying at 0.1% CO2, but if that's what you believe you have been sold a lie, or you are talking about 1% instead of 0.1%. If you think all the thousands of studies are wrong on this point, please cite references.

You have it completely the wrong way round with regard to photorespiration as well. Yes, photorespiration is bad, but as atmospheric CO2 increases up to 0.1%, photorespiration DECREASES, making photosynthesis much more efficient. It is the SUPPRESSION of photorespiration by CO2 enrichment that makes enrichment so useful.

You are muddled on the C3 and C4 classifications as well. Most grasses are not C4 photosynthesizers, though some are: the most well-known C4 photosynthesizer is maize (=corn in American English). Rice is C3, NOT C4, though they are trying to genetically modify it to C4.

Aug 17, 2010 at 10:48 PM | Unregistered CommenterScientistForTruth

An interesting history lesson is given here on how the climate affected the Roman Empire
( adversely ) due to its affect on agriculture

Aug 18, 2010 at 12:11 AM | Unregistered CommenterRoss

ScientistForTruth --

Thanks for the reply about ozone effects (Aug 17, 2010 at 3:09 PM). Ever so much more informative than the website I cited.

Aug 18, 2010 at 2:11 AM | Unregistered CommenterHaroldW

German physicist/government adviser Hans Joachim Schellnhuber on plant food:

Take agriculture, for example. If temperatures rise, harvests will suffer, in cereal crops, for example. But at the same time the higher level of CO2 in the atmosphere will lead to improved fertilization of plants. This fertilization from the air will make up for a large portion of the heat damage, perhaps even overcompensating for it. In other words, we could even get higher yields for a certain amount of time, provided there is enough water.,1518,712113,00.html

Aug 18, 2010 at 10:45 AM | Unregistered Commenterharold

Interesting mention of a reassessment of the demise of the Woolly Mammoth on BBC radio this morning, which now blames warming climate change. Unable to resist a mention of CO2, the reporter explained that this had risen at the same time, but (obviously) due to natural causes. Sadly, he didn't follow through and explain that this was a consequence of the warming and not the cause...

Aug 18, 2010 at 12:48 PM | Unregistered CommenterJames P

I've just found the link:


Which contains this: "They found that the cold and dry conditions during the ice age, with reduced concentrations of carbon dioxide, didn't favour the growth of trees."

C'mon Pallab Ghosh, now think!

Aug 18, 2010 at 12:57 PM | Unregistered CommenterJames P

Harold "But at the same time the higher level of CO2 in the atmosphere will lead to improved fertilization of plants. This fertilization from the air will make up for a large portion of the heat damage, perhaps even overcompensating for it." Increased CO2 not only makes plants more robust to heat and cold, but shifts their optimum temperature for photosynthesis to higher temperature.

Put it another way, if CO2 increases we will see improved yields at all temperatures. But we will be able to harness even greater yields if there is warming as well. So, for gradually increasing CO2 and no warming we will see improvements. The combination of a gently warming world with gradually increasing CO2 levels is fantastic for plants. A very bad combination would be warming without an increase in CO2. Whether warming is natural or anthropogenic, it is in our interests for food security later this century to increase CO2 levels as much as we are able. I can only imagine that, having studied the effects of CO2 on plants, some people would like to reduce carbon emissions as a way of reducing world population - by starvation, of course.

Aug 18, 2010 at 5:06 PM | Unregistered CommenterScientistForTruth

Thanks you for your responses. The information I posted above wasn't simply invented, but drawn from the following sources:
Lodish, H., Berk, A., Zipursky, S. L., Matsudaira, P., Baltimore, D. and Darnell, J. Molecular Cell Biology. W. H. Freeman and Company; 1999, New York, New York. Pp. 667-669
Daniel, R. Taub, Miller, Brian and Allen, Holly. Effects of elevated CO2 on the protein concentration of food crops: a meta-analysis. Global Change Biology (2008 Blackwell Publishing Ltd). No. 14, pp. 565–575.
Mark Pagani, Katherine H. Freeman, Michael A. Arthur. Late Miocene Atmospheric CO2 Concentrations and the Expansion of C4 Grasses. Science 6 August 1999. Vol. 285. No. 5429; pp. 876 - 879; from where we can read:
"Evidence suggests that C4 grasses expanded rapidly during the late Miocene (~8 to 4 Ma). Characterized by the Hatch-Slack photosynthetic pathway, C4 plants (largely but not exclusively represented by grasses) can internally concentrate CO2 before carbon is fixed by way of the Calvin cycle and subsequently avoid the energetic costs of photorespiration. This physiology provides C4 plants with a competitive advantage over C3 plants (which lack a CO2-concentrating mechanism) when the ratio of atmospheric CO2 to O2 concentrations is low."
I wouldn't place too much confidence in studies consisting only of measurements of the final length and weight of plants grown in greenhouses rather than on more accurate analysis using the protein research procedure (PRP) and chromatography. By using PRP and chromatography the amount of protein and carbohydrates a plant has produced can be accurately measured, thus allowing us to know whether production has increased or decreased from the influence of a given environmental factor -- nutrients, insolation, available gases, etc. Sometimes one can be deceived when appreciating only growth and weight because it may have been gained by non-living structures; cell wall or fat globules, for example. On the other hand, by measuring directly the food that a plant is producing, the results are more accurate and actual.

Aug 18, 2010 at 6:11 PM | Unregistered Commentertom

Tom: The quote seems to confirm what everyone else has been saying here: that C4 plants have an advantage in low-CO2 atmosphere and don't respond as favorably to higher CO2 levels. So are you withdrawing your claim that C3 plants fare badly in 0.1% CO2, or are you implying that it is documented in one of these studies? If it is the latter, which one of them?

Aug 18, 2010 at 6:22 PM | Unregistered CommenterDagfinn

Tom: so you trot out references, but NONE that support your assertions about 0.1% CO2 being deleterious - LETHAL, was the word you suggested - to plants.

Just as we all know as per your Pagani et al quotation, C4 plants have the advantage over C3 plants at low CO2 concentrations. That's why all the studies agree that CO2 enrichment is of limited (but some) use for C4 plants, but highly beneficial for C3 photosynthesizers.

Your Science Daily report (incredibly badly written and misleading, I might add) doesn't support your position one little bit. The results of the experiment "designed to simulate environmental conditions that climate experts predict may exist 100 years from now: a doubling of atmospheric CO2; a temperature rise of 2 degrees F; a 50 percent increase in precipitation; and increased nitrogen deposition – largely a byproduct of fossil fuel burning" showed an increase of 40% under those conditions, and "when higher amounts of CO2 gas were added to plots with normal temperature, moisture and nitrogen levels, aboveground plant growth increased by nearly a third."

Lodish et al doesn't support your position either - that shows that photorespiration inhibits photosynthesis - yes, we all know that: that's why CO2 enrichment works because it can get through partially closed stomata and inhibit photorespiration.

Taub et al demonstrate that under certain conditions of increased CO2 protein concentration can reduce, but of course they solve this potential problem by offering the obvious solution: for farmers to breed grain varieties that have higher concentrations of proteins under conditions of increased CO2. In other words, concentration will only suffer if there are no changes in farming practices over the next hundred years, and the likelihood of that is NIL. Farmers will grow varieties that can exploit the elevated CO2 to full effect. What's more, this study is talking about concentration, not yield. If I increase my yield by 50% and lose protein concentration by 10%, don't I still end up with a huge amount more protein per acre?

Anyway, returning to your initial post, are you going to withdraw your assertion that 0.1% CO2 is lethal to all but "about 100 plant species around the world"? You haven't been able to back it up, and it's a lie.

Aug 19, 2010 at 2:41 PM | Unregistered CommenterScientistForTruth


Lodish et al doesn't support your position either - that shows that photorespiration inhibits photosynthesis - yes, we all know that: that's why CO2 enrichment works because it can get through partially closed stomata and inhibit photorespiration.

Photorespiration inhibits photosynthesis; it is true. CO2 enrichment up to 1000 ppm inhibits photosynthesis on C3 plants. Here an extract from Lodish book, page 670:

"Photorespiration, a wasteful process that competes with photosynthesis... In C3 plants, much of the CO2 fixed by the Calvin cycle is lost during photorespiration."

And again, from Lodish book, page 670:

"However, the net rates of photorespiration for C4 grasses, such as corn and sugar cane, can be two or three times the rates for otherwise similar C3 grasses, such as wheat, rice, or oats, owing to the elimination of losses from photorespiration."

The same argument is repeated on page 667.

On the other hand, concentrations above 550 ppm of CO2 makes the plant inhibits its production of stomata conducting to serious physiological problems for C3, C4 and CAM plants.


Nasif S. Nahle

Aug 19, 2010 at 7:40 PM | Unregistered CommenterNasif Nahle

Nasif S. Nahle: What sort of foul game are you playing? References have to be relevant: if you cite references and mangle references that don't support your assertions you come across as pretty daft, or worse.

Your assertion is "CO2 enrichment up to 1000 ppm inhibits photosynthesis on C3 plants." That's a blatantly false assertion. Your quotes from Lodish et al don't support that position in the slightest. There's no connection whatsoever between the assertion and the quotes. And you finish off with another false assertion, for which you give no reference whatsoever: "concentrations above 550 ppm of CO2 makes the plant inhibits its production of stomata conducting to serious physiological problems for C3, C4 and CAM plants." Whatever 'production of stomata' is supposed to be you don't say. I challenge you to find any references in the literature that support the view that concentrations of CO2 above 550 ppm cause 'serious physiological problems for C3, C4 and CAM plants'. Until you and Tom cite some references that support your bizarre assertions it's clear that you are just out to spread disinformation.

Readers of this blog please note the following disgraceful disinformation:

Your supposed quote from Lodish is a lie. You cite Lodish as

"However, the net rates of photorespiration for C4 grasses, such as corn and sugar cane, can be two or three times the rates for otherwise similar C3 grasses, such as wheat, rice, or oats, owing to the elimination of losses from photorespiration."

What Lodish actually says is

"However, the net rates of photosynthesis for C4 grasses, such as corn or sugar cane, can be two to three times the rates for otherwise similar C3 grasses, such as wheat, rice, or oats, owing to the elimination of losses from photorespiration."

You have substituted the word 'photorespiration' where Lodish has 'photosynthesis'. Very naughty.

I notice that you also deliberately removed the very important words from a quote by Lodish. You cite him as

"Photorespiration, a wasteful process that competes with photosynthesis... In C3 plants, much of the CO2 fixed by the Calvin cycle is lost during photorespiration."

What Lodish actually says is

"Photorespiration, a wasteful process that competes with photosynthesis, is favored at low CO2 and high O2 pressures (see Figure 16-50). In C3 plants, much of the CO2 fixed by the Calvin cycle is lost during photorespiration."

So, as I said, it is LOW CO2 that favours photorespiration and makes photosynthesis inefficient in C3 plants. Lodish, properly quoted, destroys your assertion. High CO2 suppresses photorespiration and improves photosynthetic efficiency. Figure 16-50, reference to which you deleted, also deliciously destroys your argument, as the caption says

"CO2 fixation, reaction (1), is favored by high CO2 and low O2 pressures; photorespiration, reaction (2), occurs at low CO2 and high O2 pressures (that is, under normal atmospheric conditions)."

But of course you knew that all along didn't you, that's why you left out the critical words. So you, sir, are simply a shameless deceiver.

Aug 19, 2010 at 11:55 PM | Unregistered CommenterScientistForTruth

Aug 19, 2010 at 11:55 PM | ScientistForTru

"You have substituted the word 'photorespiration' where Lodish has 'photosynthesis'. Very naughty."

No, you're the solitary liar here. I copied exactly the words from MY book "Molecular Cell Biology" by Lodish et al. Stop decieving your readers.

Aug 20, 2010 at 1:43 AM | Unregistered CommenterNasif Nahle

On this paragraph:

"However, the net rates of photorespiration for C4 grasses, such as corn and sugar cane, can be two or three times the rates for otherwise similar C3 grasses, such as wheat, rice, or oats, owing to the elimination of losses from photorespiration."

I made a mistake on writing "photorespiration" instead "photosynthesis". I apologize for my error. However, Lodish confirms what I said about the inefficiency of photorespiration in comparison with photosynthesis and the inferiority of C3 plants under CO2 stress in comparison with C4 plants. Each biologist on this world knows that photorespiration is a primitive unproductive process, which is reaffirmed as Lodish says:

"In C3 plants, much of the CO2 fixed by the Calvin cycle is lost during photorespiration."


Nasif S. Nahle

Aug 20, 2010 at 2:00 AM | Unregistered CommenterNasif Nahle

Nasif Nahle. You are digging yourself into a deeper hole and making yourself look like a fool. What point are you trying to make? You say "Each biologist on this world knows that photorespiration is a primitive unproductive process, which is reaffirmed as Lodish says:

"In C3 plants, much of the CO2 fixed by the Calvin cycle is lost during photorespiration.""

Big deal - we all know that. And your point is?

The point that you seem to be missing, which is very clear in the literature, including Lodish et al, is that as CO2 is increased in the atmosphere photorespiration in C3 plants decreases and carbon fixation increases, so photosynthesis becomes much more efficient. You can't get away from that fact, in spite of your bluster. Your argument that "CO2 enrichment up to 1000 ppm inhibits photosynthesis on C3 plants" is in tatters, and destroyed by Lodish et al themselves, as I showed.

And you haven't yet given us the reference to your silly assertion that concentrations of CO2 above 550ppm cause "serious physiological problems for C3, C4 and CAM plants."

In your posting at 2.00am you finally admit that you made the substitution of the word "photorespiration", but at 1.43am you had called me a liar and deceiver for correctly pointing out that you had done that very thing, which at that time you strenuously denied. So now you admit that what I said was true, but you haven't yet had the decency to retract the false remarks you made about me.

I see you're careful to avoid reference to the other quotation you had made from Lodish et al, where I showed you had carefully edited out the very words and reference to a diagram that destroys your case.

I'll let the readers judge whether you have an ounce of credibility left.

Aug 20, 2010 at 10:30 AM | Unregistered CommenterScientistForTruth

I wonder if Tom and Nasif are the same person (though the syntax of the posts I think suggests they are different people). SfT, you've done a sterling job at digging the background out. I find it so much more interesting reading the papers than the press releases.

Nasif, I hope you take on board SfT's thorough reading of the issue. It is very rare that things are cut and dried in science, and I suggest you take a more curious approach to learning in depth about a subject, rather than believe the snippets presented (with 'spin') in press reports. You'll find that science is a quest for truth (and a very interesting one at that) not an absolute statement of it.

Aug 20, 2010 at 6:24 PM | Unregistered CommenterCumbrian Lad

Like this?

or this?

or this?

Perhaps this one is science:

or this one:

You don't know to whom you're addressing your insults.

Aug 22, 2010 at 5:48 AM | Unregistered CommenterNasif Nahle

From the statement of William Happer before the
Select Committee onEnergy Independence and Global Warming, May 20, 2010

We are all aware that “the green revolution” has increased crop yields around the
world. Part of this wonderful development is due to improved crop varieties, better use
of mineral fertilizers, herbicides, etc. But no small part of the yield improvement has
come from increased atmospheric levels of CO2. Plants photosynthesize more
carbohydrates when they have more CO2. Plants are also more drought-tolerant with
more CO2, because they need not “inhale” as much air to get the CO2 needed for
photosynthesis. At the same time, the plants need not “exhale” as much water vapor
when they are using air enriched in CO2. Plants decrease the number of stomata or air
pores on their leaf surfaces in response to increasing atmospheric levels of CO2. They
are adapted to changing CO2 levels and they prefer higher levels than those we have at
present. If we really were to decrease our current level of CO2 of around 400 ppm to the
270 ppm that prevailed a few hundred years ago, we would lose some of the benefits of
the green revolution. Crop yields will continue to increase as CO2 levels go up, since
we are far from the optimum levels for plant growth. Commercial greenhouse operators
are advised to add enough CO2 to maintain about 1000 ppm around their plants.
Indeed, economic studies like those of Dr. Robert Mendelsohn at Yale University project
that moderate warming is an overall benefit to mankind because of higher agricultural
yields and many other reasons.

Aug 22, 2010 at 7:41 AM | Unregistered Commenterharold

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