Introducing their study, Duval et al. (2012) note that atmospheric CO2 enrichment might logically be expected to lower plant nutrient concentrations (i.e., dilute them), due to the greater rate of carbohydrate production elevated CO2 concentrations induce in plants via their stimulation of the photosynthetic process, the end result of which in the case of agricultural crops has been hypothesized by Loladze (2002) to result in “hidden hunger,” i.e., more – but less nutritious – food. But is that expectation borne out by experimental studies?
In a herculean effort to find the answer to this question, Duval et al. conducted a meta-analysis of the subject that was designed to include the results of all CO2 enrichment studies of all plant nutrients that had been conducted and published in the peer-reviewed scientific literature up to the time of the commencement of their analysis. More specifically, they say that they quantified “elevated CO2 effects on leaf, stem, root, and seed concentrations of B, Ca, Cu, Fe, K, Mg, Mn, P,S, and Zn among four plant functional groups and two levels of N fertilization,” based on 90 individual experimental analyses involving a total of 478 independent replications. So what did their analysis reveal?
What did it reveal? Essentially, a whole lot of nothing significant, one way or the other. But since that in itself contradicts the nutrient dilution idea, mission accomplished.