Intensification Has Reduced Carbon Footprint Of U.S. Crop Production

LEXINGTON, KY.
   In the scientific community, it is widely accepted that the global climate is changing, and that human activities are a principal cause of this. Many human activities produce “greenhouse gases”. These transparent gases are present at trace concentrations in the Earth’s lower atmosphere. However, they have the unique quality of trapping heat there. This trapped heat is driving many of the recent changes in the Earth’s climate, including rising global temperatures. See the UK Extension publication, Agriculture’s Contributions to Climate Change: Not the “Top Dog” (http://bit.ly/LrXozR) for more information on sources of greenhouse gases in the U.S.
   Policymakers worldwide are seeking ways to reduce emissions of greenhouse gases, so that we can reduce the disruptive impacts of climate change on water supplies, food production, human health, and extreme weather. Since carbon dioxide is the most important greenhouse gas, policymakers often speak of reducing our “carbon footprint”.
   Agricultural producers sometimes feel blamed for climate change, especially in the media. However, U.S. crop producers might be pleasantly surprised to learn that recent research in the world’s top science journals tells a different story.
   Recently, four prestigious research papers emphasized how crop intensification is an important way to reduce the carbon footprint of agriculture. A key point I take away from these papers is rather simple: For every acre of land that we cultivate, we should grow as much food as is reasonably possible, with as little carbon emission as possible.
   U.S. producers excel at crop intensification through agronomic/ horticultural improvement. For example, astonishing increases in grain yields have been achieved in the U.S., yet yields continue to rise (Fig. 1). Remarkable yield increases have been achieved in horticultural crops, as well (Fig. 2).
   Our high-production agriculture stands in contrast to the situation in many developing countries, where crop yields are quite a bit lower. In such countries, the path to producing more food often is to bring more land under cultivation, which can increase the carbon footprint of food production by as much as three times. Pound-forpound of food produced, U.S. farmers have significantly reduced the carbon footprint of food production.
   While U.S. agriculture has served us very well over the years in providing abundant, safe food, we can do even more to reduce the carbon footprint (Extension agents can help with this). U.S. producers would probably agree that the ultimate goal is sustainable intensification: keeping the yield gains made in intensification while continuing to improve the sustainability of our agricultural production systems. But it is also worth recognizing that the success U.S. producers have had in intensifying crop production has helped to reduce climate change.
   Bibliography
   1. Foley et al, 2011. Solutions for a cultivated planet. Nature, Volume 478, pages 337-342, http://bit.ly/MdA5yo.
   2. Grassini and Cassman, 2012. High-yield maize with large net energy yield and small global warming intensity, Proceedings of the National Academy of Sciences, Volume 109. Pages 1074-1079, http://bit.ly/KhTQCe.
   3. Tilman et al, 2011. Global food demand and the sustainable intensification of agriculture. Proceedings of the National Academy of Sciences, Volume 108, pages 20260-20264, http://bit.ly/KfNC3L.
   4. West et al, 2010. Trading carbon for food: Global comparison of carbon stocks vs. crop yields on agricultural land. Proceedings of the National Academy of Sciences, Volume 107, pages 19645–19648, http://bit.ly/KcjEEu.
   Reviewed by Dr. Mike Crimmins (University of Arizona), and Dr. David Van Sanford, Kevin J. Lyons and Greg Henson (University of Kentucky). Δ
   DR. PAUL VINCELLI: Extension Professor and Provost’s Distinguished Service Professor, University of Kentucky