Climate Change and Crop Yields: Beyond Cassandra

摘要

The effects of increasing atmospheric carbon dioxide (CO_2) concentrations on climate have been a source of worry for decades, but the positive effect of increasing CO_2 levels on crop growth has been a silver lining in the climate change cloud. Hundreds of studies, some dating back decades, have shown that most major food crops respond positively to increasing CO_2 concentrations, because of the direct stimulatory effect of CO_2 on photosynthesis and the indirect effect of decreasing the water requirements of crops. The former effect should make crops more productive and the latter more drought-tolerant. Yet a new analysis of recent and far more realistic studies based on the free-air concentration enrichment (FACE) technique, reported by Long et al. on page 1918 of this issue (1), sounds a cautionary note.