The GP is talking about a "greening effect" on the Earth due to CO^2, but the article you've linked to and this quote is talking about how the nutritional conte

The GP is talking about a "greening effect" on the Earth due to CO^2, but the article you've linked to and this quote is talking about how the nutritional content of plants for human consumption might suffer with more CO^2. Unless you think that the only thing that's "good for plants" is their suitability for being eaten by humans this seems like an unrelated issue. The vast majority of the Earth's plant biomass isn't going to be eaten by humans. You're not going to nibble on the oak tree in your back yard, but increased CO^2 in the air will make it more efficient at sequestering carbon. It's not going to be some amazing increase in perceived growth rate. The CO^2 level indoors is often 2-3x what it is outside, and people already grow plants in those conditions.