Hmmmm.... personally I question his comment that since farmers provide "fertilizer" to make their plants grow well, that growing techniques aren't part of the problem.
Putting plants on junk food (NPK Fertilizer) makes them grow quickly without needing to work in cooperation with soil microbes and it's the presence of and active interaction with microbes that makes the difference in the availability of a number of micronutrients. When researchers do clinical trials, they try to eliminate as many possible variables that they can, so if the goldenrod was grown in dirt with fertilizer, it might well show some of the changes for reasons other than the presence of higher levels of
CO2. That said, higher levels of CO2 are likely to be a factor in plants growing bigger faster - I've read that they've linked it to larger growth rings in
trees for example.
Similarly, even if it's not the whole story, I know that plants are being bred for many characteristics that don't benefit the nutritional content - think those ginormous California strawberries for example.
So I do agree that increasing the level of CO2 in the atmosphere is probably a factor in the nutritional content of the food, and I think that concern alone is a good reason to work on sequestering carbon whatever way we can on our
land, but I also think there are other things we
should be doing (like improving our soil microbe diversity) that will help to decrease CO2 *and* improve the micronutrients in our food.
Who was that guy anyway?