The level of carbs and nutrients in your diet would seem to determined by your dietary choices by an overwhelmingly larger degree. Are you eating french fries or kale?
Does it really matter if my zucchini is slightly less nutritious when I could just eat broccoli rabe instead? Or that my green beans have a trace of carbs when I'm eating a potato on the side? In supermarkets today we've never had greater choice or variety, especially in winter, at least if you're willing to pay for it -- but even in terms of paying for it, food today is the cheapest it's ever been.
I think this research is a good first step. What I think would be good to study next is to try to find how the CO2 levels can interact with other factors like the ones I listed above, as well as other ones agriculture researchers likely know about that I don't. Perhaps nothing will come of it. Perhaps something cool would come of it. Wouldn't it be awesome if researchers discovered a way to bioengineer food plants, such that by pulling extra CO2 out of the atmosphere, they grow in an extra-nutritious manner?
First, that breeding is more important than CO2. That's easy to address as it was discussed in the article. Researchers compared a weed that has had no human cultivation and also compared the genetics of samples from the 1850s, only to find that their protein concentration has declined by 33% since the industrial revolution. Additionally, the main scientist in the article published a meta study that had enough data to account for noise and it isolated CO2 as having an impact on our nutritional density.
Second, another prominent critique I'm reading here is that the conclusions are not important because other factors have so much more importance. I think this criticism is misguided and it's treating the problem as if this were big O or something. Like, "sure, this may be happening but then people could just eat spinach instead of broccoli, problem solved." There's so much that's wrong with this I don't even know where to start, actually.
"... calcium, potassium, zinc and iron ... drop by 8 percent ..."
It seems to be that the CO2 issue directly affects the inputs, making one input far more abundant than it used to be. To the degree that plants were constrained by CO2 as input, it logically leads to dilution of nutrients - unless you specifically bred plants that grew slower and produced lower yields, which seems unlikely.
(The actual mechanism, around plant's self-regulating water management affecting how much it retains vs needs to take in via the ground, is unlikely to be bred for one way or another.)
What is important is speed and scale. I.e. making most plants less nutritional by 5-10% within 50 years is something very new.
