I thought the implication of the article, though, based on their research, was that this plant did not use all of the extra CO2 to grow, but used some of it to produce more growth inhibitor which then cause crops to not grow. i.e. the experiment showed that the extra CO2 does not impact all plants in the same way, and does not necessarily impact plants in a way that is to the benefit of crops.

The problem is that not all plants will win there, and probably not the plants we rely on: for the higher CO2 levels to be useful to a plant, it needs to be growth-bound by carbon acquisition.

Guess what no fertiliser I've ever heard of contains? Carbon. Carbon and oxygen are the two things agriculture has no need whatsoever for. If anything, higher carbon level might make agricultural products worse by making the plants grow faster at the cost of nutritional content.

My understanding is that, while plants thrive overall, higher CO2 in the atmosphere is expected to “dilute” the nutrients in farm crops because they will grow too fast[0]. These nutrients may already be impacted by industrial agriculture practices[1]. So it’s still not good news for humans.

[0] https://www.nationalgeographic.com/culture/article/140507-cr...

[1] https://news.utexas.edu/2004/12/01/study-suggests-nutrient-d...

Citation needed.