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Surface Ozone Pollution Damages Rice Production in China

Yield Losses Could Endanger Global Food Security

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Rice stalks filled with grain
嘿嘿视频 and Chinese scientists have found a way to create disease-resistant rice with high yields. (Zhudifeng/Getty Images photo)

Quick Summary

  • Rice yield drops when surface-ozone levels are high
  • Rice production loss could endanger global food security
  • Policies should target rice plants鈥 key growth stage

High levels of surface ozone are damaging rice yields at an alarming rate in China, the world鈥檚 largest agricultural producer and one of its most polluted nations, report researchers at the University of California, Davis, and in China.

For the first time, the research team identified a specific stage of the rice plant鈥檚 development as being vulnerable to ozone pollution, which they warn has the potential to impact the international rice market and compromise global food security.

鈥淎s ozone levels increase in China, this form of pollution threatens to not only decrease the nation鈥檚 rice production but also affect the broad, global rice market,鈥 said the study鈥檚 lead author Colin Carter, a professor of agricultural and resource economics at 嘿嘿视频.

鈥淚n order to better design regulatory policies that help alleviate ozone pollution and protect China鈥檚 rice crop, it鈥檚 essential to develop a better understanding of the complex relationship between ozone and rice production,鈥 said Carter, whose research has for many years focused on China鈥檚 grain markets.

Findings from the new study are reported today in .

Rice production in China

Rice is China鈥檚 most important agricultural crop. In 2015, China鈥檚 rice crop was 206.4 million metric tons, 30 percent of the global crop that year.

Although it is aiming to achieve 95 percent self-sufficiency in rice, China is now the world鈥檚 largest rice importer and is expected to continue in that position for the next decade.

Around the world, most rice is consumed within the countries where it is grown, leaving only 8 percent of global rice production to be traded internationally in an average year. This causes the price of rice sold on the international market to be extremely sensitive to small changes in production.

Ozone pollution and rice productivity

Surface ozone refers to the ozone found in the troposphere 鈥 Earth鈥檚 lowest atmospheric layer extending about 20 kilometers, or nearly 12.5 miles, above sea level. This surface ozone lies below 鈥渢he ozone layer,鈥 which occurs in the Earth鈥檚 stratosphere, or upper atmosphere.

With China鈥檚 rapid growth and development in recent decades, more vehicles, power plants and refineries have been emitting nitrogen oxides 鈥 the chemical building blocks for atmospheric ozone.

For this study, the researchers examined existing air quality data as well as rice yield statistics from the 2006, 2008 and 2010 growing seasons in five provinces of Southeast China.

The researchers designed their model to take into account annual variations such as weather, fertilizer use and natural disasters, which also could impact rice yield. They found that for every additional day when the surface ozone level topped 120 parts per billion, there was a 1.12 percent loss in rice yield, compared to every additional day when surface ozone was less than 60 parts per billion.

鈥淚f this level of rice yield reduction occurred throughout all of China, it would lead to the loss of about 2 million metric tons of rice annually, which equals about one-third of China鈥檚 current annual rice imports,鈥 Carter said.

Seasonal timing key to ozone鈥檚 rice crop damage

Interestingly, the researchers discovered that the harmful effects of ozone pollution were not the same for every stage of the rice plant鈥檚 development. In fact, the increased levels of ozone only led to rice yield reductions during the time when the rice plants were forming their 鈥減anicles,鈥 the flowering spikes at the tip of the rice stalks, where the grain eventually forms.

鈥淭his is important because it indicates that regulatory policies can be most effective in protecting rice yields if they address the period of time when rice plants are in the panicle-formation stage of growth,鈥 Carter said.

Collaborators and funding

Working with Carter on the study were Xiaomeng Cui and Professor Dalia Ghanem, both of 嘿嘿视频; Aijun Ding and Fei Jiang, both of Nanjing University in Nanjing, China; and Fujin Yi and Funing Zhong, both of Nanjing Agricultural University, also in Nanjing, China.  

Funding for the study was provided by the Giannini Foundation of Agricultural Economics and the National Natural Science Foundation of Science of China.

Media Resources

Colin Carter, 嘿嘿视频 Dept. of Agricultural and Resource Economics, 530-304-7603, cacarter@ucdavis.edu

Pat Bailey, 嘿嘿视频 News and Media Relations, 530-219-9640, pjbailey@ucdavis.edu

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