|Allen, Leon - Hartwell|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 1/17/1997
Publication Date: N/A
Citation: Interpretive Summary: Concentrations of carbon dioxide (CO2) and other greenhouse gases have been rising at an alarming rate. Increases of these gases might cause global warming and adversely affect crop yields. On the other hand, CO2 is plant food; through photosynthesis it is used for plant growth. The Food and Agriculture Organization (FAO) of the United Nations held a Workshop on "Global Climate Change and Agricultural Productivity" to assess the effects of rising CO2 and potential climate changes on crops. Based on the effects of elevated CO2 and temperature on soybean, rice, and a broad range of other plants, we firmly concluded that the CO2 fertilization effect is real. Most crop yields increase about 33% and water use decreases about 10% for a doubling of CO2. Furthermore, decreases in rainfall are more detrimental for yields than rising temperatures. Irrigation can offset lack of rainfall, but water availability may decrease as irrigation requirements increase. Finally, plant selection for greater tolerance to temperature, changes of planting dates or crop species, and other plant or cropping management modifications were suggested for improving yields in a higher CO2 world.
Technical Abstract: Concentrations of carbon dioxide (CO2) and other greenhouse gases have been rising rapidly. The objectives of this paper were to assess the effects of elevated CO2 and potential climate changes on crop yields. Effects of elevated CO2 and temperature on two important crops, soybean and rice, were examined in detail, and reviews of the effects of CO2 on a range of other plants were summarized. Crop model predictions of CO2 and climate change effects on productivity and economic well-being were also reviewed. Finally, plant modification and crop management adaptations for improving productivity in a higher CO2 world were suggested. The data demonstrate that the CO2 fertilization effect is real. Most studies report increased yields of about 33% for a doubling of CO2, and decreased water use of about 10%. Potential decreases of rainfall are more serious for rainfed agriculture than increases of temperature. Irrigation can offset lack of rain, but water availability may decrease as irrigation requirements increase. Since climate model predictions of rainfall differ widely, it remains to be seen whether specific regions will become wetter or drier as global temperatures rise.