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Potential decrease in plant nutrition due to increased atmospheric CO2  RSS feed

 
Jennifer Richardson
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Interesting article I came across discussing an emerging body of research indicating that as plants have more access to CO2 in the atmosphere, they produce more sugars and carbohydrates and proportionally less micronutrients, protein, etc. Essentially they can grow bigger/faster, but the good stuff gets "diluted" and they move increasingly toward junk food status, and of course this effects animals as well moving up the food chain. One means of improving nutrient status in humans that occurs to me is the increased consumption of very low calorie but micronutrient rich foods such as teas, tisanes, leafy greens etc. since otherwise for a given daily calorie ration one's nutrient intake would gradually decrease inversely to rising CO2 levels. Of course healthier soils etc. help with nutrient density of food but unfortunately this nutrient dilution due to CO2 increase seems to be something that permaculturally grown foods will also be subject to if this hypothesis proves correct. Perhaps testing for and selecting based on nutrient density when breeding new varieties will gain traction? I wonder if you can get your produce tested as you can your soil.

http://www.politico.com/agenda/story/2017/09/13/food-nutrients-carbon-dioxide-000511?lo=ap_a1
 
James Freyr
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I read the article and it is interesting, and certainly merits more research. I did notice in the article there was no mention of any data being gathered from plants grown in remineralized soils containing all the necessary minerals and abundant soil biota to grow healthy crops, so one can only assume that the crop nutrient data they did collect comes from industrial agriculture practices which of course will result in plant mineral levels lower than decades past. Also in the article a correlation of increased plant sugars to increased atmospheric CO2 is noted which certainly may be true, but they used the umbrella term "sugars" with no distinction between simple mono and di saccharides and complex polysaccharides. The bugs we consider pests that love to devour our crops like simple sugars, and do not like complex sugars. To me the article represents a narrow focus blaming CO2 to poor crop nutrition, that lower atmospheric CO2 levels would result in more nutritious food while turning a blind eye to the source of plant nutrition, the soil they're grown in.
 
David Livingston
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I was undewhelmed by this as well . I expected to read an advert about multi vitamin pills as soon as it ended.
The connection between cause and effect was not clear enough for me as it could be due to a host of other factors not counted or seemingly considered .
Also who paid for this research ?

David
 
Jennifer Richardson
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I agree, I would like to see data from plants grown in remineralized soils, but they did mention several experiments such as the algae experiment and the FACE experiment which controlled for soil quality and isolated CO2 as the experimental variable, and they looked at wild goldenrod and historical strains of grain to attempt to control for factors such as plant breeding that selects for yield, transportability, etc in favor of nutrition. Not saying that all this is bulletproof, but it does tend to confirm that CO2 is the salient factor, and soil quality and selective breeding at least are not sufficient to explain the altered nutrient profile. They've done controlled experiments, not just population studies; there is more to the data than merely attempting to pass correlation off as causation. However, despite poor soil quality seeming not to be the causative factor based on the data presented, I would like to see the degree to which higher soil quality could compensate for the problems induced by higher CO2 levels.

I would also like to know more about the "sugars" and "carbohydrates" they mention; unfortunately some of the linked peer-reviewed journal articles are paywalled, as per usual, although not all of them, and even the ones that are paywalled mostly have an abstract and (more usefully) a bibliography freely available. I have read some but not all of them and would be happy to discuss them in more depth as time and the annoyance of typing on my cell phone permits (I no longer have a laptop). It might be worth clicking through and exploring if time permits. James, I think your point about the sugar type/content as it relates to pest control is an interesting one and a potential avenue for further exploration.

As for who paid for the research, I can't say at the moment, but it seems that Loladze had difficulty getting funding for years due to the interdisciplinary nature of his research, which surprises me not at all based on my experience of academia, and it looks like at least one of his articles was sent back from peer review three times (ouch!) before being accepted, which may or may not inspire confidence, but certainly doesn't seem to indicate that there is some sort of corrupt conspiracy facilitating him, although I know that anything with the word "CO2" attached tends to make people think there's a political agenda involved.

I think the CO2 hypothesis is plausible and supported by the data, although the research suffers from the same lack of an holistic perspective that almost all mainstream agricultural research does.
 
David Livingston
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I was not thinking about the CO2 angle it just that I have read verious claims that foods becomming less nutriment rich over the years  The classic being oranges having less vitamin C . This is usually tied in some how with the suggestion of buying vitamin pills thus my cynicism .
As for this research still mmmm yes CO2 might have this effect on some plants but all - for me this is too generic a supposition
 
Jennifer Richardson
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Agreed, David--most of the research seems to focus on the class of plants that include major staple grains and legumes; probably bad news for global nutrition but not as relevant for permaculturists. Actually, identifying plant species that maybe don't react this way (or not as much) to rising CO2 levels might be an interesting avenue of research. And I agree, I have been aware for years of declining nutrient levels in produce but always put it down to soil quality, chemical fertilizers, new plant varieties etc. I was somewhat perturbed to read that rising CO2 levels were also contributing, since that is more difficult to compensate for than is improving soil or selecting heirloom/wild plant varieties.
 
Marcus Billings
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My two cents for what it's worth:

Although it's hard to tell because the article didn't specify, but it looks like the studied crops were the modern "staple foods", potatoes, wheat, barely, and rice (based on the caption under the pic at the bottom).  The plant foods that have always been highest in carbs and lowest in nutrient content anyway!  Every reputable diet I've looked at says stay away from them altogether, or only in small amounts.  All of these genetically modified plants have been developed specifically for increased carbohydrates. 

And, as James mentioned, the probable commercial fields being used are being depleted every year of their mineral content, not to mention the organic matter that is being lost. 

It may very well be that increased CO2 makes plants bigger overall, which given the finite mineral resources that "any" plant's roots have access to, might mean that a bigger plant has less minerals per volume, but I doubt if the the total amount of nutrients is affected.  As an example, if I mixed 3 teaspoons of food color in a pint jar, it would be a brighter color than if I mixed the same 3 teaspoons into a gallon container. 

I would say in the case of leafy greens the amount of increased sugar is a very, very small percentage, if at all.  Too many variables in this articles that are NOT discussed to take it too seriously.  And Politico has been known to be biased. 

I'll wait to hear about a double blind spinach study on no-till soil before I get too worried about this!
 
duane hennon
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Marcus Billings wrote:My two cents for what it's worth:

Although it's hard to tell because the article didn't specify, but it looks like the studied crops were the modern "staple foods", potatoes, wheat, barely, and rice (based on the caption under the pic at the bottom).  The plant foods that have always been highest in carbs and lowest in nutrient content anyway!  Every reputable diet I've looked at says stay away from them altogether, or only in small amounts.  All of these genetically modified plants have been developed specifically for increased carbohydrates. 

And, as James mentioned, the probable commercial fields being used are being depleted every year of their mineral content, not to mention the organic matter that is being lost. 

It may very well be that increased CO2 makes plants bigger overall, which given the finite mineral resources that "any" plant's roots have access to, might mean that a bigger plant has less minerals per volume, but I doubt if the the total amount of nutrients is affected.  As an example, if I mixed 3 teaspoons of food color in a pint jar, it would be a brighter color than if I mixed the same 3 teaspoons into a gallon container. 

I would say in the case of leafy greens the amount of increased sugar is a very, very small percentage, if at all.  Too many variables in this articles that are NOT discussed to take it too seriously.  And Politico has been known to be biased. 

I'll wait to hear about a double blind spinach study on no-till soil before I get too worried about this!



I totally agree
if you put some algae in a glass jar with some nutrients and increase the sunlight
the algae will continue to grow until it hits some limiting factor
this is just basic nutrition
you don't need a math degree to understand this


a better experiment is that as you increase the sunlight, you also increase the available minerals in the  jar
and then check for nutritional quality

and  with a identical jar
increase the sunlight, increase the minerals, AND the CO2
then check for nutritional quality
I predict both will show continued increase production and nutrition
up until you reach some limiting factor,ie, space, minerals, CO2, etc
an eight grade science experiment


politico is political
and the article is just more "the CO2 is falling from the sky" chicken little nonsense
 
Jennifer Richardson
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Marcus, yep, the research focuses on C3 plants, which include wheat, rice, and soybeans. Unfortunately all trees are also C3 plants, as are ~85% of plants on the planet. C3 designation has to do with the Calvin cycle and how the plants fix carbon during photosynthesis.

As I mentioned, they did control for soil quality, mineral content, etc. and used wild plants and heirloom strains to control for some of the issues you mentioned, such as genetic modifications, etc. The FACE methodology is the gold standard for isolating CO2 as a variable so data indicates that this effect is independent from the problems we see from soil depletion, selective breeding for commercial traits, etc. Those things are known problems, what I am getting at here is that increasing atmospheric CO2 is an additional factor which exacerbates those problems and which as permaculturists we are not necessarily "safe" from just because we are forest gardening on healthy soils, for instance.

I agree with you on things like spinach, which is why I mentioned leafy greens in my original post as a potential workaround. Unfortunately very few people in this world get the bulk of their calories from spinach, and the implication of this research is that <em>even for plants grown in a permaculture setting</em>, the micronutrient content and ratio of protein to carbohydrate of a diet consisting of a given number of calories will gradually decline with rising CO2 levels unless the proportions of verious plants in the diet changes. I agree with you that it's basically a dilution effect (like food coloring in water), which means that you must consume ever more calories to get the same amount of nutrition, if all other factors hold steady. This is not ideal, which is why I suggested increasing consumption of very low-calorie foods such as teas/tisanes and leafy greens to compensate.

I also think this has a lot of future research potential, such as: What food plants do not respond in this manner to increasing CO2 levels or do so only minimally (possibly C4 or CAM plants) and does it make sense to grow more of them? How can we feasibly select for plants that take up and store increased amounts of micronutrients, protein, etc.--is this even possible on the home scale? Does the CO2 effect have implications for pest predation (micronutrients are often natural pesticides and sugars often attract pests)?
 
Jennifer Richardson
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Duane, did you read about the algae experiment in the article or did you read any of the linked journal articles?

I don't normally read Politico so no comment on its bias but the citations are accessible enough, and have nothing to do with Politico.

Obviously algae or most anything else will uptake more nutrients up to a certain limit if they are increasingly available in its growth medium. The point being made by the researchers is that given identical growth media (soils, in real life) plants exposed to higher CO2 concentrations grow faster/bigger but with increased carbohydrate:protein ratios and decreased micronutrient content per unit.

I don't get "the sky is falling" out of that, but I don't think the idea of CO2 affecting plant growth is a very extreme idea!
 
Marcus Billings
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Jennifer Richardson wrote:Marcus, yep, the research focuses on C3 plants, which include wheat, rice, and soybeans. Unfortunately all trees are also C3 plants, as are ~85% of plants on the planet. C3 designation has to do with the Calvin cycle and how the plants fix carbon during photosynthesis.

As I mentioned, they did control for soil quality, mineral content, etc. and used wild plants and heirloom strains to control for some of the issues you mentioned, such as genetic modifications, etc. The FACE methodology is the gold standard for isolating CO2 as a variable so data indicates that this effect is independent from the problems we see from soil depletion, selective breeding for commercial traits, etc. Those things are known problems, what I am getting at here is that increasing atmospheric CO2 is an additional factor which exacerbates those problems and which as permaculturists we are not necessarily "safe" from just because we are forest gardening on healthy soils, for instance.

I agree with you on things like spinach, which is why I mentioned leafy greens in my original post as a potential workaround. Unfortunately very few people in this world get the bulk of their calories from spinach, and the implication of this research is that <em>even for plants grown in a permaculture setting</em>, the micronutrient content and ratio of protein to carbohydrate of a diet consisting of a given number of calories will gradually decline with rising CO2 levels unless the proportions of verious plants in the diet changes. I agree with you that it's basically a dilution effect (like food coloring in water), which means that you must consume ever more calories to get the same amount of nutrition, if all other factors hold steady. This is not ideal, which is why I suggested increasing consumption of very low-calorie foods such as teas/tisanes and leafy greens to compensate.

I also think this has a lot of future research potential, such as: What food plants do not respond in this manner to increasing CO2 levels or do so only minimally (possibly C4 or CAM plants) and does it make sense to grow more of them? How can we feasibly select for plants that take up and store increased amounts of micronutrients, protein, etc.--is this even possible on the home scale? Does the CO2 effect have implications for pest predation (micronutrients are often natural pesticides and sugars often attract pests)?


Hi Jennifer,

I'm guessing you were able to access the white papers for these studies, because I saw nothing in the article that accounted for the mineral content of the growing medium itself.  As I said, it's quite possible that higher CO2 levels may cause a reduction of mineral uptake, however, since the FACE program only isolates the CO2 variable, I don't think it's fair to say that all plants growing today are essentially becoming "junk foods" as the article intimates.  For the sake of argument we can say that both the control and the experimental group had comparable soils, but who's to say that either one were of a high quality.  Again, I would like to see all the variables.  Most universities are growing in commercial fields near the schools using Big Ag principles.  (I've seen Purdue University projects firsthand)  And soil conservation/building, much like preventive medicine in healthcare, is very often the last thing that is looked at by academia.  (Thanks a lot Monsanto)

On the casual observation side of it, I know from my own experiences that good soils lead to good plants.  One only has to look at the increase in plant growth and vitality when amending the calcium and phosphorus of the soil.  Also, I've done my own Vitamin C tests on my produce versus store bought and have found between 5 and 10 times higher levels in mine (iodine test).  (yes, I know this does not directly relates to mineral uptake)  If only minerals were like vitamins where we could actually see them in the vegetables and fruits!  Produce grown in good soils are still packed with more than enough nutrients to sustain us. We just need to get everyone we can on board with planting anything and everything at every opportunity so that we can sequester the excess CO2!  I think the earth will take care of itself if we just stop paving every patch of ground and building so many facilities with all this dead roof space. 

I guess what I'm saying is that we are a long way from starving regardless of how much we eat like the tribbles on the Starship Enterprise .


 
duane hennon
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It’s also difficult, but not impossible, to run farm-scale experiments on how CO2 affects plants. Researchers use a technique that essentially turns an entire field into a lab. The current gold standard for this type of research is called a FACE experiment (for “free-air carbon dioxide enrichment”), in which researchers create large open-air structures that blow CO2 onto the plants in a given area. Small sensors keep track of the CO2 levels. When too much CO2 escapes the perimeter, the contraption puffs more into the air to keep the levels stable. Scientists can then compare those plants directly to others growing in normal air nearby




one of the studies

http://www.nature.com/nature/journal/v510/n7503/full/nature13179.html?foxtrotcallback=true

Dietary deficiencies of zinc and iron are a substantial global public health problem. An estimated two billion people suffer these deficiencies1, causing a loss of 63 million life-years annually2, 3. Most of these people depend on C3 grains and legumes as their primary dietary source of zinc and iron. Here we report that C3 grains and legumes have lower concentrations of zinc and iron when grown under field conditions at the elevated atmospheric CO2 concentration predicted for the middle of this century. C3 crops other than legumes also have lower concentrations of protein, whereas C4 crops seem to be less affected. Differences between cultivars of a single crop suggest that breeding for decreased sensitivity to atmospheric CO2 concentration could partly address these new challenges to global health.



so the gold standard FACE
artificially holds the CO2 level constant
something that doesn't happen in a normal field
who knows, maybe this is causing problems

one has to be always wary of starting assumptions  used in experiments
 
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