Submitted to: Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2006
Publication Date: 6/30/2006
Citation: Long, S.P., Ainsworth, E.A., Leakey, A.B., Nosberger, J., Ort, D.R. 2006. Food for thought: Open-air field experiments suggest lower than expected crop yield stimulation with rising [CO2]. Science. 312:1918-1921. Interpretive Summary: We investigated the effects of higher carbon-dioxide levels in large-scale trials of major crops, such as rice, wheat, soybeans and corn. The plants were grown under realistic field conditions, rather than in experiments using enclosures that have traditionally been employed to maintain constant levels of the gas around plants. The field results show that elevated carbon dioxide stimulates crop yields less than previously thought. While earlier experiments using enclosures indicated wheat yields would shoot up 31 per cent if the plants were grown in the higher carbon-dioxide environment expected to prevail around the middle of this century, the new research using an open-field test indicated the increase will be only 13 per cent. For soybeans, the increase dropped from 32 per cent to only 14 per cent, while for corn, the expected yield rise of 18 per cent in a high carbon-dioxide world dropped to no yield change at all. If models of future food supply are based on the chamber studies, then they are likely overly optimistic.
Technical Abstract: Model projections suggest that while increased temperature and decreased soil moisture will act to reduce global crop yields in 2050, the direct fertilization effect of rising carbon dioxide concentration ([CO2]) will more than offset these losses. The CO2-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 [CO2] under fully open air field conditions. In FACE trials, elevated [CO2] enhanced yield ~50 % less than in enclosure studies, casting doubt on projections that rising [CO2] will fully offset losses due to climate change.