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!
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)?
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
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.