Positive Feedback Accelerates- Rice Agriculture Can Worsen Global Warming

by Project Censored
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Researchers from University of California, Davis, Northern Arizona University and Trinity College in Dublin, Ireland published research, which claims that the global warming process is making rice agriculture produce more greenhouse gases (GHG), in the Oct.22, 2012 edition of journal Nature Climate Change.

With more and more carbon dioxide being emitted into the atmosphere with rising global temperatures, global warming becomes a serious environmental problem. However, researchers recently found out something worse. They claimed that rice will emit more methane, another GHG, into the atmosphere if the concentration of carbon dioxide and the global average temperature keep increasing. In other words, Global Warming’s effects make rice paddies emit more methane, and the newly produced methane will aggravate Global Warming. Scientists refer to this process as a loop of positive feedback. Once the positive feedback effect gets to a relatively high level, it will be extremely difficult to stop or decelerate global warming.

Moreover, although rice is not the most popular staple in U.S., it is indispensable for people in Asia, Africa and South America. Since those areas are heavily populated, rice becomes the second-most consumed food in the world. In addition, although people always connect methane emission with livestock, in fact, rice paddies are the number one manmade source of methane. Moreover, compared to carbon dioxide, methane is a much stronger GHG. Therefore, the extra methane produced by rice may bring significant negative effects on climate change. Thus, Kees Jan van Groenigen, the co-author of the study, referred to rice agriculture as less “climate-friendly.” However, this less “climate-friendly” staple may still need to play an important role to “ensure a secure global food supply” in this population explosion era for a long time, according to Professor Bruce Hungate from Northern Arizona University.

When the research team finished collecting data from over sixty rice paddies, the researchers used a statistical method named meta-regression analysis to explore the correlation among the concentration of carbon dioxide, temperature and the GHG intensity of those rice paddies, which refers to the yield-scaled emission. Increased atmospheric concentration of carbon dioxide can lead to a 31.4 percent increase of rice’s GHG intensity. Also, the GHG intensity of rice will increase by 11 percent if the temperature increases by 1 °C. Although the increasing temperature is relatively less influential to rice’s GHG intensity compared to the increasing concentration of atmospheric carbon dioxide, Chris van Kessel, the co-author of the study, still believes that with the two factors co-effecting, the amount of methane produced by one kilogram may double by the end of this century.

Although the current result of the study seems to be disappointing, the researchers pointed out that several methods could reduce the negative effects. For example, rearranging sowing date and using alternative fertilizers may help to decrease the emission of methane.

The researchers provided solid evidence that increased atmospheric carbon dioxide and increased temperatures can increase rice paddy’s emission of methane, and then intensify the current global warming situation. This result shows that Global Warming is not far away from people’s daily life. And more importantly, most of the potential factors of global warming, in this case rice agriculture, are reacting in undetectable ways. Although it is hard for everyone to accept the fact that his or her daily diet is connected with global warming process, people have to focus on the ecosystem more and avoid damaging it. Researchers in this case did bring some potential ways to reduce methane emission of rice. However, compared to these methods, which are like treating the symptom, it is more important to make people recognize the significant hazards of global warming and then encourage people to make efficient actions to reduce these hazards.

Source: “Rice and Global Warming” Andy Soos, Environmental News Network, Oct. 24, 2012


“Rice Found to Accelerate Global Warming” Kat Kerlin, University of California News Pages, Oct. 22, 2012


“Increased Greenhouse-gas Intensity of Rice Production under Future Atmospheric Conditions” Kees Jan van Groenigen, Chris van Kessel, Bruce A. Hungate, Nature Climate Change, Oct. 21, 2012


Student Researcher: Weiqing Zhang & Parker Schwartz

Faculty Instructor: Prof. Kevin Howley

Evaluator: Prof. Jeanette Pope, Geoscience Department

DePauw University