Any middle-schooler groks the fundamentals of photosynthesis: Fueled by sunlight, plants turn carbon dioxide and water into sugar and oxygen, which they use to grow stems, roots, leaves, and other tasty bits. As CO2 levels continue to rise—we’re on track to double pre-Industrial levels in the next few decades—it might sound like we’re in for a vegetational boom. But any greenery growth spurt will come with a downside. CO2-charged sprouts contain more starches and sugars, and fewer minerals and proteins. You can try to avoid junk food, but our plants are getting junkier too.
See, plants also require proteins in order to grow, which they synthesize using elements they draw from the soil, such as nitrogen, phosphorus, and potassium. In the course of sucking up those molecules, greens also take in nutritious minerals like zinc and iron. Plants often absorb more than they need, storing the excess in their cells. Then humans get to eat them.