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I have no disagreement with the claim that higher levels of CO2 increases plant growth. That is a fact. I seriously doubt the 30% claim without compelling evidence, though. Especially for agriculture, where water limits are rarely the concern and we dump fertilizer like it's free.

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Actually our use of fertilizer and irrigation makes CO2 level a significant limiter on plant growth rates. CO2 fixation is so expensive that plants adapted to arid environments have developed a better way of doing it, C4 carbon fixation.

I found the study: https://wattsupwiththat.com/2017/04/05/study-suggests-increa...

That's an interesting study but I fail to see that it supports your claim. There's no mention of C4 fixation in the article, nor any claim that CO2 fixation is a significant limiter for agriculture.

The article claims 30% increase in general (not just agricultural), but also does not attribute all that simply to more available CO2.

Your own claim is self-contradicting as you use arid environments as the basis for your claim. Agricultural environments where plants are irrigated are not arid, by definition.

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