My answer to a Quora question...
No. That "Great Nutrient Collapse" Politico story is propaganda, not science.
The 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.
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, of course, that is not the case. Studies show that food grown in greenhouses at elevated CO2 levels has about the same nutritional value as food grown in open fields at ambient CO2 levels.
Permalink: https://tinyurl.com/Loladze
Regrettably, Mr. Burton answer shows no awareness of the state of human nutrition. His statements about the CO2 studies on plant nutrition are remarkably off mark.
The objections he raised are among those misconceptions that the fuel industry backed organizations and so-called “science” outlets have use to seed doubt about the progressing decline of the quality of crops and wild plants.
Here I’ll briefly list two claims by Mr. Burton followed by evidence contradicting his claims:
Dr. Loladze, it is passing strange that you would quote a fragment of what I wrote, and then cite a source that agrees with what I wrote, in fact if not emphasis, as evidence that what I wrote was incorrect. Perhaps you did not understand it?
I wrote (and you quoted the first sentence of), “The 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.”
The source you cited says, “Higher concentrations of CO2 stimulate growth and carbohydrate production in some plants, but can lower the levels of protein and essential minerals in a number of widely consumed crops, including wheat, rice, and potatoes…”
Do you not understand that the two statements are in agreement?
Most studies do not find a net protein or micronutrient reduction due to CO2 fertilization, because the increase in growth rates is greater than the protein or micronutrient level reductions.
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:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2773101/
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!”
Scientific American: Carbonic Acid Gas to Fertilize the Air
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. Studies show that food grown in greenhouses at elevated CO2 levels has about the same nutritional value as food grown in open fields at ambient CO2 levels.
Here's an excellent literature review on the topic:
http://www.co2science.org/subject/p/summaries/protein.php
Excerpt:
“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.”
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
Greenhouses are controlled environments were both CO2 and soil are enriched restoring the balance. I enjoy eating plants grown in greenhouses. If Mr. Burton could magically enrich all the soils on earth with all the essential minerals to the same degree as CO2 is rising, I’d rest my case.
I think we are in agreement, then: With inadequate fertilization, the higher growth rates from higher CO2 levels can result in lower levels (though not lower overall production) of various nutrients, but with adequate fertilization that is not a significant problem.
Well, then we come full circle, Mr. Burton. Fertilization of soils with elements essential for humans such as iron, zinc, calcium, selenium, chromium, and magnesium is almost non-existent. But CO2 is rising all around the globe. Name me one agricultural field that is not affected by rising CO2. None. The increasing imbalance between what’s in the atmosphere and in the soil, leads to less nutritious crops and wild plants. I challenge you to read my “stoichiometric thought experiment” that I made back in 2002 to logically deduce what would be proved years later to be true empirically and find any mistake in it. You can read it here: https://www.researchgate.net/pub...
Lowering plant growth rates, e.g., by lowering CO2 levels, to make crops more nutritious, is like burning down the smaller houses in your neighborhood to improve property values: It improves only the average. The total goes down, rather than up.
Furthermore, it amazes me that you think, “Fertilization of soils with elements… such as iron, zinc, calcium, selenium, chromium, and magnesium is almost non-existent.” Let me google that for you:
fertilizers containing iron - Google Search
fertilizers containing zinc - Google Search
fertilizers containing calcium - Google Search
…etc.
What’s more, dietary shortages of such micro-nutrients are easily resolved through very inexpensive nutritional supplementation. In the case of iron, it can be as simple as cooking in cast-iron pots.
(Also, it is my understanding that chromium content in soil is more apt to be too high, than too low, and chromium nutritional deficiency is rare.)
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 micro-nutrient. 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.
Mr. Burton, you misinterpreted my statement: “ Fertilization of soils with elements essential for humans such as iron, zinc, calcium, selenium, chromium, and magnesium is almost non-existent.” Obviously, mineral fertilizers exist, who doubts that? But most agricultural soils are routinely fertilized with N-P-K and not other minerals — simply because this is what boosts yields.
Dr. Loladze, I understand perfectly well what “almost non-existent” means. Did you click the links I gave you?
The google search for “fertilizers containing iron” returns over nine million hits. The searches for “fertilizers containing zinc” and “fertilizers containing calcium” return over four million.
Likewise, a google search for fertilizers containing magnesium returns over six million hits:
fertilizers containing (magnesium OR "epsom salts") - Google Search
When you said that such fertilizers are “almost non-existent,” you were wrong. They are very, very common.
Farmers fertilize with what their soils lack, and what their crops need. E.g., when they lack iron, farmers fertilize with iron.
That is as true for open field agriculture as it is for greenhouses. You’ve already acknowledged that greenhouse crops, grown very rapidly at 1200 to 1500 ppmv CO2, are nutritionally comparable to crops grown outdoors. How do you suppose that can be, if you really believe both that mineral shortages are common, and that fertilization with such minerals is “almost non-existent?”
Fertilization with nitrogen, phosphate & potash is more common than fertilization with iron and other minerals simply because farmers fertilize with what their soils need, and shortages of those minerals are less common than shortages of nitrogen, phosphate/phosphorus & potash/potassium.
Additionally, when you say that shortages of minerals do not impact crop yields, you’re wrong about that, as well. Iron and other minerals are essential for healthy plants. If you don’t believe me, look up “chlorosis,” or read about Russ George and his famously successful experiment fertilizing the ocean — with iron!
The bottom line is that, 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.