At Current CO2 Concentrations, Plants are Close to Starving
Acting in concert, the several phenomena described in the preceding subsections, as well as other phenomena possibly yet unknown, typically allow the growth-enhancing effects of atmospheric CO2 enrichment to be expressed in the face of severe resource deficiencies. But what happens in the case of "carbon starvation," when the air is deficient in CO2?
Because CO2 is the basic "food" of essentially all plants, the more of it there is in the air, the bigger and better they grow; and as the air's CO2 content declines, so too do plant growth rates decline. And when a critically-low CO2 concentration is ultimately reached, starving plants lacking sufficient CO2 - like starving people lacking sufficient food - actually die, as indicated in the figure below, where plant death occurs when dry weight production falls to zero.