Food for Thought: Lower-Than-Expected Crop Yield Stimulation with Rising CO ₂ Concentrations

TLDR

Model projections predict that rising CO₂ fertilization will offset yield losses from warming and drying, but the CO₂ fertilization factors were based on enclosure studies from two decades ago. Free‑air concentration enrichment (FACE) technology has enabled large‑scale trials of major grain crops at elevated CO₂ under fully open‑air field conditions. The FACE trials showed that elevated CO₂ increased yields by about 50% less than enclosure studies, undermining the expectation that CO₂ fertilization will fully offset climate‑change losses.

Abstract

Model projections suggest that although increased temperature and decreased soil moisture will act to reduce global crop yields by 2050, the direct fertilization effect of rising carbon dioxide concentration ([CO 2 ]) will offset these losses. The CO 2 fertilization factors used in models to project future yields were derived from enclosure studies conducted approximately 20 years ago. Free-air concentration enrichment (FACE) technology has now facilitated large-scale trials of the major grain crops at elevated [CO 2 ] under fully open-air field conditions. In those trials, elevated [CO 2 ] enhanced yield by ∼50% less than in enclosure studies. This casts serious doubt on projections that rising [CO 2 ] will fully offset losses due to climate change.