Claim: CO2 will make our crops like non-nutritious filler material

“Our research makes it clear that decisions we are making every day–how we heat our homes, what we eat, how we move around, what we choose to purchase–are making our food less nutritious and imperiling the health of other populations and future generations,” said Sam Myers, lead author of the study and principal research scientist at Harvard Chan School.

The study will be published online August 27, 2018 in Nature Climate Change.

Presently, more than 2 billion people worldwide are estimated to be deficient in one or more nutrients. In general, humans tend to get a majority of key nutrients from plants: 63% of dietary protein comes from vegetal sources, as well as 81% of iron and 68% of zinc. It has been shown that higher atmospheric levels of CO2result in less nutritious crop yields, with concentrations of protein, iron, and zinc being 3%-17% lower when crops are grown in environments where CO2concentrations are 550 parts per million (ppm) compared with crops grown under current atmospheric conditions, in which CO2 levels are just above 400 ppm.

For this new study, researchers sought to develop the most robust and accurate analysis of the global health burden of CO2-related nutrient shifts in crops in 151 countries. To do so, they created a unified set of assumptions across all nutrients and used more detailed age- and sex-specific food supply datasets to improve estimates of the impacts across 225 different foods. The study built on previous analyses by the researchers on CO2-related nutritional deficiencies, which looked at fewer foods and fewer countries.

The study showed that by the middle of this century, when atmospheric CO2 concentrations are expected to reach around 550 ppm, 1.9% of the global population–or roughly 175 million people, based on 2050 population estimates–could become deficient in zinc and that 1.3% of the global population, or 122 million people, could become protein deficient. Additionally, 1.4 billion women of childbearing age and children under 5 who are currently at high risk of iron deficiency could have their dietary iron intakes reduced by 4% or more.

The researchers also emphasized that billions of people currently living with nutritional deficiencies would likely see their conditions worsen as a result of less nutritious crops.

According to the study, India would bear the greatest burden, with an estimated 50 million people becoming zinc deficient, 38 million becoming protein deficient, and 502 million women and children becoming vulnerable to diseases associated with iron deficiency. Other countries in South Asia, Southeast Asia, Africa, and the Middle East would also be significantly impacted.

“One thing this research illustrates is a core principle of the emerging field of planetary health,” said Myers, who directs the Planetary Health Alliance, co-housed at Harvard Chan School and Harvard University Center for the Environment. “We cannot disrupt most of the biophysical conditions to which we have adapted over millions of years without unanticipated impacts on our own health and wellbeing.”


Meanwhile, there’s still lots of squawking over nutritionally enhanced golden rice.

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Richard Kiser
August 27, 2018 4:17 pm

Time to buy stock in GNC?

Reply to  Richard Kiser
August 27, 2018 6:08 pm

IIRC…there are about 800 million people in the world considered starving…
…I doubt if they care that their food is a little less nutritious, if they actually get to eat

These studies always leave out the fun parts….

Reply to  Latitude
August 28, 2018 8:14 am
Patrick J Wood
August 27, 2018 4:18 pm

Nothing wrong with the Frankenfood that they are forcing on the public these days, but nonexistent “global warming” is going to destroy the nutritional value. This would be amusing, if not so sad and unbelievable what the alarmists will come up with next.

Reply to  Patrick J Wood
August 27, 2018 4:26 pm


Actually the premise — although poorly stated — is that additional CO₂ loading of the atmosphere will drive many food-species to produce more food per hectare, all other inputs static. And more food will divide the mineral-type and protein-from-metabolism type nutrients to a lower portion of the increased output of foodstuffs, per kilogram.

I don’t think they’re wrong. Quantitatively supportable? Dunno. But the effect is real, and has been verified in doubly-controlled studies.

And 550 ppm CO₂ is coming.
We can thank China and India, Africa and Central America for most of that.


Max Hugoson
Reply to  GoatGuy
August 27, 2018 4:36 pm

Please produce a “study”. I’m still saying the replacement for the “nutritional deficit” will come from “biologically processed” waste products.

Reply to  GoatGuy
August 27, 2018 4:40 pm

I think you’re right about the premise. They can’t deny that more CO2=more production, so they try to make the case that mineral and protein value on a per lb basis will go down. So if (for example) you have 2X the amount of food, does a 20% drop in nutrition per pound matter much?

But as for being quantifiable, actually it is. For starters, a ton of vegetable crops come from greenhouse operations where CO2 is pumped in at 1000 ppm or more. Let’s take ONE crop as an example. Is anyone complaining that cannabis is LESS potent per ounce than it was 30 years ago? I maintain that the opposite is true and bumper crops of vegetables from green house operations are just as, if not more, nutritious than their “open air” counterparts despite heavy doses of CO2.

Beyond that, we’ve been doing the experiment regarding increased production versus nutrition for decades. Here’s the World Bank data on the matter:

Obviously production has increased dramatically in the last few decades due to everything from irrigation to pest control to weed control to fertilizer. Are we to believe that a 2X to 3X increase in production from those means resulted in food that is just fine but an increase in production from CO2 will somehow be different?

I think not.

bit chilly
Reply to  davidmhoffer
August 27, 2018 4:55 pm

that reads like a perfectly clear and concise rebuttal david.

Reply to  davidmhoffer
August 27, 2018 5:01 pm

David nailed it….of course
They don’t qualify what “less nutritious” is…is it 1 mg less of iron
….and they don’t qualify how many less people will starve to death

Let’s face it, the people they are talking about are on the edge already…what’s more important….1 more gram of iron? when they only get 1 tomato?…..or 1 less gram of iron when they get a dozen, enough tomatoes to make a huge lasagna and feed the whole family?

1 less gram of iron in 1 tomato…when 10 people have to share that 1 tomato…that’s what they are talking about

..and David is right, this is trying to make some lame case about CO2 being bad

Reply to  davidmhoffer
August 27, 2018 5:36 pm

I agree with David. Another angle would be to suppose that CO2 levels are reduced and ask what the planr would do. As CO2 levels got lower and lower, and the plant struggled more and more to grow, could you seriously tell me that the plant would become more and more nutritious, hitting maximum nutrition just before it died???

Reply to  Mike Jonas
August 27, 2018 5:41 pm

Mike, you sorta hit on it…
They are saying the parts of the plant that we eat are less nutritious…
…but the plant itself does not show any nutrient deficiencies

Plants blow up with water when exposed to higher CO2 levels.
What they are measuring is nutrients diluted with water.

Reply to  davidmhoffer
August 27, 2018 6:06 pm

Yes, I can personally vouch for grapes grown in greenhouses in Spain having just as high an alcohol content as grapes NOT grown in greenhouses. Maybe higher. The Rioja reds must be respected, you know, and likewise, the Vina Fuerte. More CO2 means more sugar in the grapes, hence, more alcohol is produced in the fermentation process….. What? Oh, uh. Never mind.

Reply to  Sara
August 27, 2018 9:56 pm

but the proportion of grape skin!
this will lead to grape skin deficiency.

Richard of NZ
Reply to  gnomish
August 28, 2018 4:52 am

So I get Rose instead of red Pinot Noir.

Reply to  davidmhoffer
August 27, 2018 7:35 pm

But David, when they smoke the more potent weed, are they getting enough zinc? Are the women and children getting enough iron? (apparently no one cares about men in any of these studies)

Reply to  GoatGuy
August 27, 2018 5:33 pm

‘All other inputs static’, but they are not.

Reply to  GoatGuy
August 27, 2018 9:51 pm

It is often stated that most people need more fiber in their diet, so I guess this development is only positive.

Reply to  GoatGuy
August 27, 2018 10:05 pm

For C3 plants, ie all trees and most crops, 550 would be better than 400 but 800-1300 would be best of all.

Mike the Morlock
Reply to  GoatGuy
August 27, 2018 10:08 pm

What is easier to ship to a at risk population? 100 lb bags of flour, or one lb bags of multiple vitamins? Some may disapprove of them, but in locations where food types are limited that is the best solution.Human beings need a minimum of food bulk to keep their digestive system healthy.The system also needs time to absorb the metals. If the individual is sickly a lack of food can prove fatal.

One more thing lack of food triggers wars in the very places where people need peace the most

Reply to  GoatGuy
August 27, 2018 10:11 pm

It’s really simple.

Given the same amount of N, but more CO2, naturally the proportion of amino acids to carbohydrates will decline slightly. But that doesn’t mean fewer amino acids, just the same, as against more sugar or starch. The obvious solution is to provide more N.

Australian study on wheat grown for three years under elevated CO2.

It’s all good.

Reply to  GoatGuy
August 28, 2018 4:27 am

Bring it on! For those who are worrying about the 400ppm of CO2 in the atmosphere perhaps they should think what to do about the 40,000ppm they exhale? I for one would welcome a collective holding of breath by those alarmists challenged as they are by mathematics and school level science.

Paul Penrose
Reply to  GoatGuy
August 28, 2018 8:54 am

You are assuming that current crops are limited by the soil as to how much of a particular nutrient they absorb. But what if they are not? In that case, there need not be any reductions in those nutrients, as long as they are added back into the soil (to prevent exhausting it).

Reply to  GoatGuy
August 28, 2018 2:27 pm

GoatGuy writes

Actually the premise — although poorly stated — is that additional CO₂ loading of the atmosphere will drive many food-species to produce more food per hectare, all other inputs static. And more food will divide the mineral-type and protein-from-metabolism type nutrients to a lower portion of the increased output of foodstuffs, per kilogram.

I guess its a good thing we can select for, and even genetically modify for, food-species that have a greater uptake of those nutrients to compensate. Plus there’s fertiliser, of course.

The idea that CO2 fertilisation of crops is “bad” is one of those where I wouldn’t want to debate on the “for the proposition” team!

Reply to  Patrick J Wood
August 27, 2018 6:22 pm

Not only is there nothing wrong with Frankenfood. In some cases it’s actually more nutritious than the natural stuff.

Terry Harnden
Reply to  MarkW
August 27, 2018 6:50 pm

DUH. Obvious dumbed down by fluoride.

Reply to  Patrick J Wood
August 28, 2018 1:46 am

too much wealth causes poverty deficiency.
it would lead to the extinction of the underprivileged.

August 27, 2018 4:23 pm

How can CO2 tell the plant not to take up minerals via the roots, when ALL CO2 does is be part of the Photosynthesis process that happens in leaves and stems?

Reply to  Sunsettommy
August 27, 2018 4:36 pm

CO2 senses how much water and other nutrients are available to the plants, and then its chi vibes with alarmist fears to stay ahead of those nutrients, by adding more mass than those nutrients can keep up with. CO2, thus, has become a sentient molecule, controlled by green-chi propaganda. It just KNOWS.

Reply to  Sunsettommy
August 27, 2018 4:41 pm

See my answer to GoatGuy above.

Reply to  davidmhoffer
August 27, 2018 4:44 pm

Saw it, davidmhoffer. Thanks.

Reply to  davidmhoffer
August 27, 2018 6:11 pm

It’s a good answer.

I was trying to point out that their claim is bogus when the soils are being properly fertilized and watered, to maintain the level of necessary elements in the soil needed for uptake in the roots to SUSTAIN the increased growth pattern that Hybrids and increased atmospheric CO2 promotes.

Reply to  Sunsettommy
August 28, 2018 12:24 pm

Yes, that’s what I was getting at — adjust limiting factors to accommodate the added CO2.

If more nitrogen would enable a more nutritious response to more CO2, then add more nitrogen. If more water would enable it, then add more water. I’m thinking that the proportions between all factors have to be right, in order for any one limiting factor (or combination of limiting factors) to maximize an increase in another (or others).

Reply to  Sunsettommy
August 27, 2018 5:17 pm

Tommy, higher CO2 causes plants to hold onto water…closed stomatas don’t let water out…what they are actually measuring when they say plants are less nutritious….is the nutrients are diluted with water…a dried up shriveled tomato will have more nutrients by weight….than one pumped up with water

…it ain’t much

Reply to  Latitude
August 27, 2018 5:55 pm

I’m still not eating the dried up shriveled tomato…..

Joe Wagner
Reply to  Sheri
August 27, 2018 6:51 pm

I would- they’re pretty tasty with some mozzarella and salami.

Reply to  Latitude
August 27, 2018 6:16 pm

The whole thing is hilarious because even with the purported TINY drop nutritionally, there are still plenty of needed nutrients in the foods anyway.

Just another laughable attempt to scare the masses over a trace molecule with a tiny IR absorption effect.

Reply to  Sunsettommy
August 27, 2018 6:29 pm

They make it sound scary…by not saying how many more people will actually get to eat

Reply to  Latitude
August 27, 2018 7:38 pm

If higher CO2 results in plants holding onto water, does that mean that agriculture would need less water for the same volume of food? If so, isn’t this a good thing?

Reply to  Sunsettommy
August 27, 2018 11:36 pm

Basically the researchers just exhaust the minerals in the soil.

The results come from ignorance of crop rotation and other normal practices.

Reply to  Sunsettommy
August 28, 2018 5:32 am

The report is woth serious critique.

August 27, 2018 4:30 pm

I find it kind of laughable: 1.3% of the world’s people will become protein deficient … because photogenic sources of protein (plants) will have their protein and minerals diluted — per kilogram — as a result of the yield-per-hectare skyrocketing (making way more food) … due to CO₂.

If somehow, those regions of the world who look most squarely at the protein and mineral deficits were to work assiduously to keep their population growth down, then the substantially engorged CO₂ fertilization production would allow them to raise more livestock, which in turn would be excellent as protein and mineral supplements.

You know?
Just saying,

Reply to  GoatGuy
August 27, 2018 5:21 pm

1.3% of the world’s people will become protein deficient …and 20% more people will actually get the eat
…they leave out the fun parts

August 27, 2018 4:33 pm

This is like Dr. Mann’s hockey stick. The hockey stick was concocted because the MWP was an inconvenient fact. Similarly, CO2 enhanced plant growth is an inconvenient fact. What to do? I know, let’s concoct a theory that cancels out the benefits of CO2 enhanced plant growth. CO2 enhancement will make us all starve of malnutrition.

The additional inconvenient fact is that CO2 enhancement is standard operating procedure in greenhouses, including for food crops. link Nobody is complaining about lack of nutrition in greenhouse food crops. It’s a deliberately concocted theory. Motivated reasoning at its worst.

Max Hugoson
August 27, 2018 4:35 pm

But, processing Bovine Excrement into a food product (which they have plenty of which to work with) will certainly compensate for that “nutritional deficit”.

August 27, 2018 4:38 pm

So this brings us back to the age old question, “which came first, the dinosaur poop or the mega fauna which it fertilized”

Curious George
August 27, 2018 4:39 pm

Harvard is the school where Naomi Oreskes is Professor of the History of Science and Affiliated Professor of Earth and Planetary Sciences. Her influence on the quality of science is undisputable.

Tom Halla
August 27, 2018 4:40 pm

Aside from being based on models, the few real facts it is based on presumed no fertilizer being used in the higher CO2 environment, which biased the plants to produce more carbohydrates and less protein. It also assumes no change in the cultivar used, and it should be practical to compensate with a different variety.

R. Shearer
August 27, 2018 4:40 pm

Well then, it stands to reason that cannibals will be forced to eat less than nutritious people. String beans will be stringier. Artichokes will make you gag, tofu will be phooey, and fish will taste fishy. 🙂

August 27, 2018 4:46 pm

Here we go again having forgotten that we have been growing plants in greenhouses for more than a hundred years.

August 27, 2018 4:54 pm

I’ll wait for the study but I think there’s trouble in River City. Reading between the lines this “study” is a model.

August 27, 2018 4:57 pm

A bit like irrigation really. Somehow they don’t seem so concerned to campaign against irrigation though.

August 27, 2018 5:04 pm

The studies I’ve read which assume nutritional dilution have been on crops grown at baseline levels of fertilisation. Adding nitrogen and trace elements to soil would seem to solve that. So, just shuddup and eat yer free lunch, fortification costs extra!

August 27, 2018 5:14 pm

In May, the USDA followed agencies in Australia and New Zealand in approving Golden Rice 2E.

Reply to  Sgt
August 28, 2018 5:30 am

Very good news.

Reply to  Sgt
August 28, 2018 7:40 am

Thanks for that link, Sgt, and that encouraging news!

Excerpt from the article:

“Alongside the continuing work on the GR2E Golden Rice variety, IRRI is also developing high-iron and zinc rice and stacked beta-carotene, iron and zinc varieties to address other micronutrient deficiencies among impoverished communities.”

kent beuchert
August 27, 2018 5:33 pm

The nutritional losses can be made up by pills, but the increased amount of food would likely be more important than any loss in percentages of protein. No mention of increased food production in a 550PPM world. Not a very thorough study. I don’t think we want to reduce CO2 levels very much from here – as I recall, levels that existed around 1860 would lead to mass starvations.

Reply to  kent beuchert
August 27, 2018 5:46 pm

Just use more nitrogen fertilizer. Amino acids (which polymerize to form proteins) require N. To make sugar, hence carbs, all you need is CO2 and H2O.

Reply to  Sgt
August 28, 2018 7:36 am

True. In fact, legumes (like soybeans, lentils, peas, chickpeas, cowpeas, beans, and peanuts) generally don’t even need more nitrogen fertilizer, because they make their own — and they benefit tremendously from elevated CO2 levels.

It is fortuitous that the highest-protein crops benefit even more than most other crops from eCO2.

Here’s a nice video of cowpea seedlings growing under varying CO2 levels:

August 27, 2018 5:58 pm

Oh. You mean such nutritionally useless foods such as taro, breadfruit, papaya,pineapple, oranges, banana/plantains, sweet potatoes, yams, coconuts, peppers, dates, tomatoes/tomatillos and mangoes, to name a few warm, if not hot weather, nutritionally loaded traditional food crops. Some of these , such as taro (tops and corms), sweet potatoes and papaya (green and ripe) are in the very top rung of nutrition.

August 27, 2018 6:00 pm

This analysis is based on “unpolished brown rice”
The vast majority of the rice consumed is white, which has most the nutrients stripped off and is just used as starch energy source.
Also the fertiliser for the faster growing CO2 enhanced crops was kept the same.
I imagine the results would be very different if the faster growing crops were given more fertiliser to compensate.

August 27, 2018 6:12 pm

The tribbles starved to death because the quadrotriticale wheat in the storage bins was impregnated with a virus that turned into an inert material in the bloodstream.

The more the organism eats, the more inert matter is built up. So after two or three days, they reached a point where they couldn’t take in enough nourishment to survive.

I suppose it’s possible to create a GMO grain that does that – makes you feel full but provides no nutrient value. Oh, wait – we have it now! It’s called JUNK FOOD!!!! That accounts for a lot of things these days.

Hah! And you guys thought you could slip that one by me. Nah…. not yet!

Bryan A
Reply to  Sara
August 27, 2018 6:50 pm

Now if you could make it without calories and still feel full, you’d have the ultimate diet food

Reply to  Bryan A
August 28, 2018 4:46 am

Yes, and your hair and teeth would fall out. You’d look GRRRREAT! 🙂

David Chappell
Reply to  Bryan A
August 28, 2018 4:51 am

Read “Good Omens” by Terry Pratchett. In it the personification of Famine, one of the Four Horsemen of the Apocalypse achieved just that.

August 27, 2018 6:24 pm

If plants need more nutrients, they expand their roots. Something that plants grown in pots can’t do.

Bryan A
August 27, 2018 6:29 pm

According to this article

Zinc deficiency can also be deadly; according to the Zinc Nutrient Initiative, 800,000 people die each year as a result of zinc deficiency diseases. Currently, around 2 billion people suffer from zinc deficiency globally.

so to have 175 million efficient would be an improvement

Bryan A
Reply to  Bryan A
August 27, 2018 6:48 pm

As far as protein deficiency goes from plants…
1 word…
Meat (Me eat)

August 27, 2018 6:58 pm

Zinc content in terms of yield in grams / square meter for various wheat cultivars grown in elevated CO2 (eCO2) has been experimentally shown to range from 11 to 25 grams more of zinc per square meter wheat grown. The average was 17 grams more zinc per square meter under eCO2.

“Dilution” of zinc concentration in terms of mg / gram for these wheat cultivars grown in eCO2 ranged from 10 to 18 mg less zinc. The average was 13 mg less zinc per gram in wheat under eCO2.

So if the wheat cultivar yields 25 grams zinc per & that cultivar’s zinc concentration only dilutes by 10 mg less zinc per gram then eCO2 plays out nicely. In contrast, if the wheat cultivar yield is only 11 grams zinc more per & that cultivar’s zinc concentration dilutes by 17 mg less zinc per gram then eCO2 is not innocuous (ex: original post concerned eCO2 causes zinc loss; although generalizing about crops).

I think it is worth understanding the potential for “dilution” under eCO2. The challenge would then be to determine (& distribute) cultivars that, like some wheat, demonstrate the least decrease of mg / gr concentration of important minerals (ex: zinc).

Incidentally, although I don’t have the time now to be precise on numbers, sulphur (a part of some proteins humans use) also is subject to “dilution” under eCO2 in those same wheat cultivars refered to above. For now let me say under eCO2 the range of increase in sulphur gr/ is less expansive than the range of zinc; & the range of decrease under eCO2 of sulphur mg/gr. is also less expansive than the range of zinc.

What needs to be understood is the average increase in sulphur gr/ under eCO2 is less than the average decrease in sulphur mg/gr concentration under eCO2. In the extreme data the maximum loss of sulphur mg/gr concentration is 4 times greater than the minimum increase of sulphur gr/ gained under eCO2.

August 27, 2018 8:07 pm

“concentrations of protein, iron, and zinc being 3%-17% lower”

Once again, studies are based upon previous minimal controlled grow area and isolated plant studies that reduced water decreased uptake choking mineral amounts.

Studies that were subsequently demonstrated to be too small and isolated, because in the big scary outside world, plants are free to grow larger root systems as the plants grow bigger.

Other cultures have utilized a plant’s constrained root system to facilitate specialty plantings, e.g. Bonzai.

Odds are, these alleged researchers did not visit commercial CO₂ enhanced greenhouses nor analyze the foods they produce.

Reply to  ATheoK
August 27, 2018 8:45 pm

Actually the cited data included free-airCO2-enrichment (“FACE”), open-top-chamber & field tunnel experiments.

Reply to  gringojay
August 27, 2018 9:43 pm

Lettuce is a good greenhouse plant that does not have an extensive root system, so I propose it is a relevant test subject. The variety “Black Simpson” amply fertilized (20-10-20 N-P-K) & given favorable envornmental conditions had under elevated CO2 (eCO2) leaves with approximately 105 to 116 ppm iron, while under ambient CO2 leaves had approximately 128 to 194 ppm iron. As for zinc the lettuce under eCO2 had approximately 29 to 30.5 ppm zinc, while under ambient CO2 leaves had approximately 40 to 44 ppm zinc. As per Table 1 in cited below research.

Fig. 2 charts eCO2 related loss of N, P, K, Ca, Mg, S, Cu, Fe, Mn & Zn. I’ll mention that there is 30% less nitrogen & over 30% less sulphur for those without time to check source,
since earlier I referred to sulphur & we use sulphur amino acids. See Grietz, et al (2016) “Elevated carbon dioxise level suppresses nutritional quality of lettuce and spinach”; free full text available on-line.

I am not suggesting lettuce is a huge nutritional component of human diets. This example is to demonstrate that under well watered & fertilized conditions, comparable to commercial greenhouse cropping, the effect of eCO2 will not automatically produce identical nutritional quality in popular edible plants.

Reply to  gringojay
August 27, 2018 9:55 pm

The only S-containing amino acids of the 22 found in proteins (of which 30 are coded for in DNA) are cysteine and methionine. It takes very little dietary S to provide enough for these amino acids. Methionine is one of the nine essential amino acids, ie those which humans can’t make, so must get from food.

Rats have ten essential amino acids.

Reply to  Sgt
August 27, 2018 10:56 pm

Methionine % in food grown under eCO2 goes down , as does glutamine . The % of phenyl-alanine (we can’t make it) goes up significantly in food grown under eCO2, as does isoleucine (we can’t make it). What am trying to point out here is total protein is not the same issue as suitability of the protein composition (ratio of aminos).

As for those favoring a mathematical solution simply eating more, of the more abundant eCO2 yield, as the method of balancing there is another factor. Food grown under eCO2
has a greater more carbon to nitrogen ratio. This plays out as higher glucose % & a higher fructose % ; which for some individuals (over-fed/under-exercised/genetics) additional volume is not neccessarily benign.

Sorry, can’t find data citation. And as ever, I am not reporting trends as absolute for all kinds of plants.

Greenhouse eCO2 always gets mentioned as an example to follow. These environments are nuanced.

All factors being optimized eCO2 (800 – 900 ppm) increases the weight of some iceberg lettuce heads by 11 – 15%; yet for some butterhead lettuce that eCO2 increases it’s head weight 16 – 36%. Also, in predominantly low light growing conditions eCO2 is also very helpful for most crops.

Greenhouses must deal with aerial temperature, light, humidity & root temperature , as well as nutrients & water. Just raising temperature & humidity to a scientificly determined level increases melon concentration of mono-saccharides. Growing cherry tomatoes at 16 – 25°C produces up to 3 times the lycopene (red color) than at too high a temperature. Cucumbers perform more protein synthesis at low temperatures & downstream increase in a certain enzyme fosters more of the bitter compound curcurbitacin C. And (since discussed minerals) strawberries under autumn light have more magnesium, copper, phosphorus and sulphur; whereas under spring light more calcium, chloride & sugar.

Reply to  gringojay
August 28, 2018 5:42 pm

“open top chamber & field tunnel”?

Lettuce benefits from substantial root growth.

In plants, restrict, constrain or limit root growth and that does affect overall plant growth.

Research, before CAGW anti-science eliminated scientific method and rigor, demonstrated that restricting the plants ability to take up nutrients reduced nutrients and minerals dependent upon the roots.

Lettuce is grown indoors, in fenced plots, outdoors and in CO₂ enhanced greenhouses; the latter lettuce growers often depend upon hydroponics, and still their lettuce plants grow substantial root masses.

USDA is a meticulous test bed for agriculture plants, both at USDA centers and in farmers fields across America.

USDA meticulously maintains a food nutrient database.
Any difference in growing, harvesting, preparation, cooking, cooked, preservation, etc. is represented by a comprehensive quantitative/qualitative chemical analysis.

USDA does not list any differences in nutrients or minerals for plants grown in CO₂ enhanced environments, hydroponics, field grown, etc.

Food quality has been extensively tested and tracked for over forty years.

August 27, 2018 8:35 pm

Wut? Don’t they make supplements anymore? I swear this world has gone full bore insane. Idiocracy was a documentary.

Clyde Spencer
August 27, 2018 9:12 pm

A similar concern was expressed during the 1970s over the impact of fertilizers. The concerns apparently were not credible. Note that the article says “lower concentrations.” The implication is that the grain or fruit will grow larger, but with similar amounts of nutrients for the entire kernel, thus lowering the amount of nutrients per unit weight. Most people are unaware that a lot of fruits and vegetables are being grown in greenhouses today with enhanced CO2 levels. No one has expressed a concern about those expensive ‘organic’ fruits and vegetables.

August 27, 2018 9:29 pm

Another predictable drumbeat in the ecofascists’ war on photosynthesis.

Hocus Locus
August 27, 2018 11:13 pm
August 27, 2018 11:49 pm

The climate activists are desperate to find a dark lining in the silver cloud of soaring crop yields and increasingly rare famines. A mathematician named Irakli Loladze is one of the most prominent promoters of the claim that CO2 fertilization makes crops less nutritious. I had a “Quora debate” with him about it, starting last September:

The tl;dr version is that, just as with studies predicting crop failures from rising temperatures, the projected ill effects of CO2 fertilization require assuming that farmers are stupid, and won’t not follow agricultural best practices.

W/r/t temperature, the climate propagandists assume farmers are too stupid to adjust planting dates and cultivar selections according to local temperatures. W/r/t the effects of CO2 fertilization on nutrition, they assume farmers are too stupid to realize that more productive crops may require adjusted fertilization practices, if nutrients are in short supply in the local soil.

Excerpts (edited):

Most studies have not found evidence that the overall nutritional value of crops is reduced by the improved plant productivity from CO2 fertilization. Rather, they’ve found that when crops are grown in iron-poor or zinc-poor soil, the larger yields may contain lower levels (though not lower overall quantities!) of those micro-nutrients. There’s no net protein or micronutrient reduction due to CO2 fertilization, because the increase in growth rates is greater than the protein or micronutrient level reductions.

As it happens, dietary shortages of those micro-nutrients are easily resolved through either fertilization or very inexpensive nutritional supplementation. In the case of iron, it can be as simple as cooking in cast-iron pots.

It is possible to contrive growing conditions in which something other than CO2 limits plant growth and health, or in which a shortage of some soil nutrient causes better crop yields to be accompanied by reduced levels of some nutrient, but such contrived conditions are easily avoided through normal agricultural fertilization practices. Under real-world conditions, additional CO2 is dramatically beneficial for agriculture, to levels far beyond what we can ever hope to reach in the outdoor atmosphere, and the nutrient value of crops grown with extra CO2 is not significantly different from other crops.

If you want proof of that fact, read up on the relative nutritional values of crops grown in greenhouses vs crops grown outdoors.

Most commercial greenhouses use CO2 generators to keep CO2 at 3x to 4x ambient levels, at significant expense. That’s an increase 6 to 10 times as great as the measly ~125 ppmv increase which mankind’s fossil fuel use has caused in outdoor levels. Greenhouse operators spend the money to keep CO2 levels that high because doing so dramatically improves the growth of most plants. If the modest increase in outdoor CO2 levels were making crops significantly less nutritious, then crops grown in greenhouses at dramatically higher CO2 levels would necessarily be dramatically less nutritious than crops grown outdoors.

But they aren’t, of course. Food grown in greenhouses at elevated CO2 levels has about the same nutritional value as food grown in open fields at ambient CO2 levels.

The faster crops grow, the more nutrients they need. Farmers know that, and fertilize accordingly (or, for nitrogen, they may plant legumes — which, fortunately, benefit greatly from extra CO2). But if you fail to follow best agricultural practices, and don’t fertilize according to the needs of your crops, then the result may be reductions in protein and/or micronutrient levels in the resulting crops.

The cause of those reductions is not higher CO2 levels, the cause is poor agricultural practices.

Inadequate nitrogen fertilization reduces protein production relative to carbohydrate production, because proteins contain nitrogen and carbohydrates don’t. Here’s a relevant paper:

Human activities (mostly fossil fuel use) have raised outdoor CO2 levels by about 125 ppmv, from about 280 ppmv to the current 405 ppmv. By comparison, commercial greenhouses typically use CO2 generators to keep CO2 levels at 1200 to 1500 ppmv, which is an increase 6 to 9 times as great.

Greenhouse operators spend the money to keep CO2 levels that high because doing so dramatically improves the growth of most plants, a fact which has been known to science for a century. Here’s an article about it from Scientific American way back in 1920; they called anthropogenic CO2 “the precious air fertilizer!”

Here’s an excellent literature review on the topic:


“Rogers et al. (1996)… observed CO2-induced reductions in the protein concentration of flour derived from wheat plants growing at low soil nitrogen concentrations, no such reductions were evident when the soil nitrogen supply was increased to a higher rate of application. Hence, Pleijel et al. (1999) concluded that the oft-observed negative impact of atmospheric CO2 enrichment on grain protein concentration would probably be alleviated by higher applications of nitrogen fertilizers; and the study of Kimball et al. (2001) confirmed their hypothesis.”

It is possible to contrive conditions in which CO2 fertilization reduces levels of some nutrients, but under real-world conditions, with farmers utilizing established agricultural best practices, additional CO2 is dramatically beneficial for agriculture, to levels far beyond what we can ever hope to reach in the outdoor atmosphere, and the nutrient value of crops grown with extra CO2, either in greenhouses (with dramatically elevated CO2 levels), or outdoors (with modestly elevated CO2 levels), is not significantly different from other crops.

Here are some additional references:

1. doi:10.1071/PP9960253

2. doi:10.1016/s0167-8809(98)00185-6

3. doi:10.1046/j.1469-8137.2001.00107.x

Reply to  Dave Burton
August 28, 2018 7:13 am

typo: “won’t not follow” should be “will not follow”.

(Sorry, there’s no “edit” button when a comment goes through moderation.)

Reply to  Dave Burton
August 28, 2018 9:31 am

Greenhouse comparisons are valid if the environmental conditions are exactly similar, ad well as CO2 levels. Even without factoring in CO2 levels higher temperatures & irradiance (light) produces some tomatoes with less sucrose & more hexose content; the sweet spot (~21-26°C, depending on cultivar) that produces the nicest sugar profile can be tightly regulated in a greenhouse unlike out in the field.

It would be interesting to review any comparison between ambient CO2 field vegetable & it in greenhouse bumped up CO2 that consistantly match their light & heat environment. Just to give perspective (without regard to CO2) the free full text is available on-line for Gautier, et al’s (2008) ” How does tomato quality (sugar, acid, and nutritional quality) vary with ripening state, temperature and irradiance”.

To be clear I’ll repeat what commented earlier. The extra greenhouse CO2 is very useful for ameliorating the usually undesirable impact of low seasonal light.

By now most have heard that eCO2 grown wheat has less gluten protein. What is less understood is that eCO2 grains develop to have a higher alpha-amylase enzyme content. The amount of this enzyme is a factor in how well wheat stores, when there is more of this enzyme in a grain that is not favorable for longest storage. Of course all that is needed everywhere would be improved storage conditions’ control.

I always read how fertiler application rates can simply be increased to compensate for any alteration from elevated CO2 (or barring that people can just take supplements. In gringolandia most of my farming neighbors already struggle to finance seasonal production & buying extra fertilizer would not be as feasible as it sounds.

Guess I should say this again: I am not decrying CO2, just think there are aspects worthy of thinking critically about since commercial greenhouses need context. I’ll also refer anyone interested, who may have missed it, to the lettuce comparison in my earlier comments above.

Reply to  gringojay
August 28, 2018 1:58 pm

I’ve had time to check the given links. The 3rd used the equivalent of 350 kg of supplemental nitrogen (“high-N”) per hectare under elevated CO2 (eCO2 of 550ppm) to ameliorate grain protein loss. I won’t price 350 kg of nitrogen fertilizer or go into issues of nitrogen leaching in fields when might try to put that into widespread practise.

In experiments conducted where dry land wheat farming is done & when the actual soil
involved already has “adequate” nitrogen (ie: not where nitrogen is otherwise deficient) quite different results are seen. With 550 ppm CO2 an additional 50-60 kg / hectare nitrogen bumps up straw’s nitrogen % (as tested by dry weight) more notably than anything else.

There was no remarkable equalizing effect on grain protein “dilution” under eCO2 in good (ie: crop land of suitable nitrogen for current CO2 grown wheat) dry land soil when provide supplemental nitrogen at an affordable level. For specific comparative ratios of grain protein discussed here see Fig. 1 of (2017) “Can additional N fertilizer ameliorate the elevated CO2-induced depression in grain and tissue concentrations of wheat on a high soil N background”; free full pdf available on-line.

Reply to  Dave Burton
August 28, 2018 11:09 am

Great post, Dave.
But they aren’t, of course. Food grown in greenhouses at elevated CO2 levels has about the same nutritional value as food grown in open fields at ambient CO2 levels.

Their inductive hypotheses and models predict nutrient-poor crops from elevated CO2. But deductive evidence – under their noses every day in the food that they eat, says that it isn’t true.

But they cling to the inductive and willfully ignore the deductive.

Karl Popper was right to warn about such as these. They bring no science, only dismal stories.

August 27, 2018 11:56 pm

Made up crap posing as science.

Ed Zuiderwijk
August 28, 2018 2:09 am

‘a core principle of planetary health’.

Now that’s what I call: hubris on a planetary scale.

August 28, 2018 5:39 am

But most of us already throw away the nutrition in wheat and rice when we eat white, not wholemeal kinds. So this ‘fact’ is in fact a lie.

August 28, 2018 11:27 am

Let’s see if I live in India, walk everywhere, can’t keep food more than a day or so, spend a great deal of time growing food and my family just has enough to eat and sometimes not. Yet if I had access to cheap and plentiful energy I could have modern conveniences. I could produce more food, my family would get more to eat, spend less time when travel was required and I could even keep food for a week or more. My children could be better educated. And my family’s lives wouldn’t be shortened due to burning dung. Gee, I wonder what I would chose?

I always find it ironic that the same people that produced this study most probably oppose GMO food.

August 28, 2018 11:44 am

“It has been shown that higher atmospheric levels of CO2result in less nutritious crop yields, with concentrations of protein, iron, and zinc being 3%-17% lower when crops are grown in environments where CO2concentrations are 550 parts per million (ppm) compared with crops grown under current atmospheric conditions, in which CO2 levels are just above 400 ppm.”

Couldn’t people just eat 3 to 17% more veggies/meal to make up the lost nutrients?

Also, doesn’t this study assume that people are eating just enough of their veggies to get the exact amount of nutrients they require? I bet the vast majority of people in the world (excluding kids) eat more then enough veggies/day and hence, are getting excess nutrients.

And this makes me think we need a global authority to make sure each of us eats the exact (and same amount globally per capita) amount of veggies in order to get the exact amount of nutrients we require. /sarc

August 28, 2018 2:41 pm

‘could result in 175 million people becoming zinc deficient . . . by 2050’

A risk I’m willing to take.

August 29, 2018 1:48 am

Dave is right. I thought exactly the same but too busy debunking other alarmist deceits to tackle this one. Eat more of the slightly depleted food? My wife now understands. When I she sees some bizarre pointless “science on the BBC, she says, “…..must have been able to get a grant for it”. Without the funding, this prsumptive half baked pseudo science(science no one can prove) would stop. Dead. It’s the people feeding the catastrophe prophestying feamonster that cause the bad science (BS). And create a career for middleclass rich kids who don’t want to work in the real world of value adding, where what you say and make have to work as advertised, or you go to jail.

Johann Wundersamer
August 29, 2018 2:17 am

As CO2 levels climb, millions at risk of nutritional deficiencies.

but the urgent problem is:

If fewer and fewer SUVs are used for the benefit of electric bikes, not enough toilet paper will be transported in family households. To the detriment of civil hygiene.

August 29, 2018 4:39 am

As it happens we have empirical evidence to test this assertion that socialism is superior to capitalism for saving the natural environment. David Legates points out recent historical examples where two modern societies were split, one part to develop for 50 years under a socialist autocracy and the other part under a free market democracy. What can we learn from these two experiments: North/South Korea and East/West Germany?

Johann Wundersamer
August 29, 2018 5:21 am

As long as these foods are “processed” by cattle, pigs, chickens, roe deer, there is absolutely no problem.

The real problem remains with the vegans.

This is the real reason why the Greens want to prohibit us from eating meat – to get rid of us.

John M. Brown
August 30, 2018 6:52 am

This is easily disputed when a person considers a few of the basic to growing vegetables for food nutrients. As plants grow more abundantly (under higher CO2 levels in nature) the increase in plant “substance/life” will put a bigger demand on the soils thus more nutrients are taken out of the soil. When the levels are not replaced that was taken out by the last crop the plants will naturally be of lesser value.
Now with that said CO2 itself has a habit of replacing the nutrients that is not present (which and in what amounts I’m not aware of at this time but going on what I have witnessed personally), but then again most people don’t seem to understand that farmers do NOT put back into the soil everything the plants take out as it grows THAT IS THE BIGGEST REASON PLANTS ARE LACKING IN TRACE ELEMENTS.
(Sorry for the caps that last part but nobody wants to listen to logic and reason anymore)

When nutrients are made in the factory they basically use to base elements that will make a plant grow, in nature the soil contains many other elements and that is where you get your nutrients from by way of the simple plant. When you constantly farm the same soil year after year non-stop without putting back in all those nutrients that get taken out each year your plants are not going to have the nutrient levels you expects.

Simple chemistry actually, you can’t extract and expect the whole to remain the same

I think Ben Franklin started a college that is still open if memory serve, there in the Ag. Dept. I think the man say they have a test plot that has been used every year since the college open with each section labeled by year and you can see the difference in corn grow from now to the year the college started.

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