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More CO2 a mixed blessing for farming

Published 15th November 2009 - 28 comments - 4937 views -

While sometimes easily disregarded as wishful thinking, it is often optimistically postulated that future farmers' yields will be more bountiful due to 'carbon fertilization' via increased atmospheric carbon dioxide (CO2) levels. But things are not that simple, unfortunately.

It is correct that CO2 is one of the main ingredients of photosynthesis and that more ingredients allows for more products. But there are also other ingredients to the formula plus a labyrinth of biochemical processes from field to food to consider. More serious speculation on increased plant growth from increased CO2 levels quickly gets complicated by pro et contra whole ecosystems considerations [4].

German spring wheat

A recent German three season "Free-Air" wheat study in 550 ppm CO2 [1] came out with some results on the plus side:"Bless the farm!" by paalia

  • 11.8% more biomass of above ground biomass (stem and ears, not leaves)
  • 10.4% higher yield 

But it also gave some results on the negative side:

  • Smaller grains (of lower market value)
  • 7.4% grain protein concentration decrease
  • Decreases in amino acid concentrations
  • Changes in mineral compositions (ie potassium and lead increase; iron and silicon decrease)
  • Fructose content increase

The study did many other findings but most not as significant as the above mentioned. There were changes in the dough characteristics too. Overall, it seems clear that rising carbon dioxide levels will change the nutritional value of our food.

What this study did was grow 13 strains of spring wheat under conditions mimicing actual farming except adding CO2. Then analysing not just the grain, but the whole plant and the flour and bread produced. The growing plants were irrigated and fertilized - thus, under conditions where plant nutrients and water never limited growth. All future crops will not be that lucky: already drought is a major problem and is presumably only to increasingly cause wilting fields under global warming. Only (conventional) farmers in well-off countries are reasonably sure to be able to fertilize and irrigate their crops in any foreseeable future while elevated levels of CO2 will not do any good to a 3rd world farmer with soils cracked and dry.

Wheat is one of the world's major food crops so even a seemingly microscopic change in it's biology could lead to enormous world population health impacts further down the cause-effect chain. The mixed (and regarding some parameters not mentioned here, unreliable) results, the single crop type and the geographical limitation of the study to Stuttgart, Germany further studies should be undertaken.

Some crops (ie maize) already has evolved a mechanism for concentrating CO2 in their leaves, meaning raised atmospheric levels will help them little. Plants in general will not be able to evolve such biochemical mechanisms to accustom themselves to the changed climate in the scope of time we humans alter nature and project food production.

Other studies

The German study is interesting because it's not from a biochemical model or a test chamber, but from an actual field. However, it only looked at rising carbon dioxide. There are many other factors to look into.

One study saw a 1ºC temperature rise reduce tree growth by 50%, ozone levels are expected to rise also which will to some degree negate the effects of more CO2, plus the CO2 could have negative effects in itself (ie via ocean acidification and an expected drop in plant biodiversity). [2]

And another Free-Air study found nitrogen and phosphorous levels to quickly limit growth if deficient (or rather, not in abundance). And considering agricultural crops for carbon sequestering purposes is not really serious thinking since their combined biomass is puny compared to forest biomass as well as fossil carbon emissions. [3]

Perhaps crops from elevated carbon dioxide futures are a bit like bodybuilders - bigger, but not necessarily better.    
"Christine Roth" by cliff1066™



[1] Högy, P., Wieser, H., Köhler, P., Schwadorf, K., Breuer, J., Franzaring, J., Muntifering, R., & Fangmeier, A. (2009). Effects of elevated CO on grain yield and quality of wheat: results from a 3-year free-air CO enrichment experiment Plant Biology, 11, 60-69 DOI: 10.1111/j.1438-8677.2009.00230.x



[2] New Scientist / Climate myths: Higher CO2 levels will boost plant growth and food production

[3] RealClimate / CO2 Fertilization

[4] Climate Change Can Supercharge Plant Growth

Category: Climate Science, Health Effects, | Tags: agriculture, co2, health, researchblogging,


Hemant Anant Jain on 15th November 2009:

Thank you Benno for this post!
I am sure that would lay to rest many doubts which have been raised about CO2 and how a simplistic theory is making some people go ballistic.
Great post.

Benno Hansen on 15th November 2009:

Glad you like it, Hemant! And I agree that a lot of climate change discussion - especially the “denial” part - is using some ridiculously simplified theories.

Aija Vanaga on 15th November 2009:

I do like that comparison with body building! Just perfect!

Lucy Setian on 15th November 2009:

Perhaps crops from elevated carbon dioxide futures are a bit like bodybuilders - perhaps bigger, but far from necessarily more healty or attractive. - Sorry, but that`s not appropriate comparison at all.

Your point that the elevated levels of CO2 will not do any good to a 3rd world farmer with soils cracked and arid, is right - it`s normal, what shall we expect from rising temperatures?More ice cream?. However, we cannot be sure how this will violate further the human health. I think that there are enough examples of human naition living in dry areas but though surviving there. I do not believe that the damages will show out so fast their aposteriori effects.

mad the swine on 15th November 2009:

“I do like that comparison with body building! Just perfect! “

I don’t.  Why is it that so many supposedly enlightened environmentalists end up turning to misogyny to ‘sell’ their product?  How does it promote your cause to shame women for their bodies?  Think of any recent ad campaign by PETA, for instance…

On topic:  while the results are interesting, I’d agree that “whole ecosystems considerations” (a nice euphemism for the collapse of the Gulf Stream, rampant desertification, etc) outweigh any possible gains or losses from CO2 concentration.  Though if maize, for instance, has adapted to take advantage of higher CO2 in one respect, it’d hardly be unthinkable to bioengineer wheat, maize, etc, to better utilize atmospheric CO2 - if the ice caps don’t melt and drown us all first…

Aija Vanaga on 15th November 2009:

@mad the swine
Its not about woman or shame for the bodies. If dive in - its about bodybuilding sentence next to the picture!

Lucy Setian on 15th November 2009:

hah I believe they don`t feel that ashamed. Nevertheless, the ad of McCruelty campaign was far more convincing in its reasons than some nude chicks.

Benno Hansen on 16th November 2009:

Disclaimer: I believe in the right of every person to persue the bodily ideals they believe in.

Bodybuilder image text cleared up a bit.

Benno Hansen on 16th November 2009:

mad the swine,

You misunderstood the part about maize.

Maize (corn) is a C4 photosynthesis plant. Meaning it can take advantage of higher everything-but-CO2 situations. Like regular photosynthesis with a turbo evolved on it. In the hot, dry, sunny equatorial areas this gives plants the ability to utilize the water and sun available, not having the “low” CO2 as a restriction.

Daniel Nylin Nilsson on 16th November 2009:

I doubt that any theory can really account for all the complexities behind a phenomenon like growing plants. On any given spot there must be many other factors than co2 that affects the outcome. So hoping for increased co2 to boost harvests seems strange to me.

Moreover, it is not only a matter about how plants will grow in a different weather. If we need to change agricultural patterns, like where we grow certain crops, it will take time and patience to fin the best solutions. I think there is a real danger that we will have to do this, but don’t really have the time…

great post smile

Federico Pistono on 17th November 2009:

Thank you Benno for an actual scientific analysis of CO2 rise in crop production, not some bizarre and improbable prediction based on… well, not based on anything, I suppose.
It’s always good to hear a voice of reason.

J.C. Moore on 17th November 2009:

Thanks for the reference. Everyone just assumes that increased CO2 will be better for plants. I forwarded your article to a biologist friend who may want to do some research on the topic.

Benno Hansen on 17th November 2009:

Thank you for your comments. This is actually my fourth post based on recent peer reviewed science. I tagged them researchblogging and can also be found via my profile at wink

Paul Montariol on 18th November 2009:

Thank you!
I prepare a post in this direction.
It is very simple:
With more CO ² less proteins!
Only the population increases and the quantity of proteins asked too. In more the rich person are increasingly numerous and eat more meat.
Blow tensions or wars!

Vitezslav Kremlik on 19th November 2009:

Interesting article.

1) The article just shows, that I was somewhat correct in my article “5000ppm…” Life can exist with much higher CO2 levels. Higher CO2 means bigger plants.

2) I think it is possible, that the old species, who are not used to higher CO2 levels, might suffer if it is too much. I think it sounds logical.

3) In 1953 Crick and Watson discovered DNA… Now we are able to design new species of plants. Species, that will utilise higher CO2 levels. We do not need to wait until they evolve on their own.

Conclusion: No species on Earth ever had so tremendous ADAPTATION capabilities as present humans. Thanks to bio-engineering for example. So why freak out? We can adapt. We can do it. We can do it. We can do it.

J.C. Moore on 19th November 2009:

Certainly life can exist at those levels. It will not be life as we know it. I’m rather attached to the world the way it is and I’d like to leave it that way for my grandchildren.

It is rather unsure whether science and technology can take care of the future. Why not just make changes now that will keep the CO2 levels at an acceptable value?

Paul Montariol on 19th November 2009:

Sometimes me must get out our nose from the window and make a turn over to change the view.
I think we must develop quickly the new energies.
They are a lot.
The CO² decrease would happen without thinking of it.

Benno Hansen on 20th November 2009:

I’m with you Moore and Montariol. Vitezslav is being reckless and naive. Considering the risks involved in GMO today I fail to see how it would be sane to gamble on being able to construct an entirely GM’ed flora for the future. Let’s play this “game” safe.

Paul Montariol on 20th November 2009:

Thank you Benno, this discussion is free!

Benno Hansen on 21st November 2009:

Can’t believe I missed Big Oil creates phony climate denial site, lies about it.

An oil and gas exploration company running a non-profit to promote rising CO<sub>2</sub> levels. Insane.

Paul Montariol on 21st November 2009:

Please, can you understand me: when I read that I think I am loosing my time.
I prefer choosing the good energy for a precise question. I think it is more constructive.

Benno Hansen on 07th January 2010: / Another Chemical Could Worsen Warming
“according to a new study, as rising carbon levels fuel more plant growth in the coming decades, Earth’s hungry greenery is going to start running low on nitrogen”

Paul Montariol on 07th January 2010:

We are living a lot of revolutions today.
The future is impredictible!

Mark on 05th May 2010:

Environmentalists are promoting their own stupidity regarding simple chemistry. Take 1 million marbles, color 6 red to represent CO2, 790,000 blue for Nitrogen, 20,100 green for Oxygen and 9000 for Argon. The rest you color black to represent Carbon monoxide, methane hydrogen helium etc.  Triple the CO2 level and nothing will happen to anything except your plants will apreciate it. They must have CO2 to give us Oxygen.

Benno Hansen on 05th May 2010:

Believe it or not, Mark: Most environmentalists and all chemists/climatologists are fully aware of the atmospheric composition however you choose to express it.

test paternité adn on 15th June 2010:

It has always been good that environmentalist do not seize in discovering new potentials or side effects of modern world. With regards to CO2 consumption of plants and nitrogen depletion in the near future,maybe,we as beings dependent in Mother nature should be aware and must work together to save and make solutions to potential problems. Always remember that BIG PROBLEMS always start to smaller ones.

Have a blessed day!

Muscle Building on 24th June 2010:

I certainly believe that too much of everything is harmful,and too less is the same. Maybe (as for my own opinion) it would be best if we maintain the equilibrium in our environment.

Muscle Building

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