A cyclical effect: More atmospheric CO2, more greenhouse gas per grain of rice

Oct 23, 2012
More Greenhouse Gas per Grain of Rice
Paddy field. Credit: Jim Hill, UC Davis. 

More carbon dioxide in the atmosphere and rising temperatures cause rice agriculture to release more of the potent greenhouse gas methane (CH4) for each kilogram of rice it produces, new research published recently in the online edition of Nature Climate Change reveals. "Our results show that rice agriculture becomes less climate friendly as our atmosphere continues to change. This is important, because rice paddies are one of the largest human sources of methane, and rice is the world's second-most produced staple crop," said Dr Kees Jan van Groenigen, Research Fellow at the Botany Department at the School of Natural Sciences, Trinity College Dublin, and lead author of the study.

Van Groenigen, along with colleagues from Northern Arizona University and the University of California in Davis, gathered all published research to date from 63 different experiments on rice paddies, mostly from Asia and North America. The common theme in the experiments was that they measured how rising temperatures and extra carbon dioxide in the atmosphere affect rice yields and the amount of methane that is released by rice paddies.

The research team used a technique called meta-analysis, a statistical tool for finding general patterns in a large body of experimental data. "Two strong patterns emerged when we analysed all the data: first, more CO2 boosted emissions of methane from rice paddies, and second, higher temperatures caused a decline in rice yields", explained Professor Bruce Hungate of Northern Arizona University and co-author of the study.

Methane in rice paddies is produced by that respire CO2, like humans respire oxygen. More CO2 in the atmosphere makes grow faster, and the extra plant growth supplies with extra energy, pumping up their metabolism. Increasing CO2 levels will also boost , but to a smaller extent then CH4 emissions. As a result, the amount of CH4 emitted per kilogram of rice yield will increase. Rising temperatures were found to have only small effects on CH4 emissions, but because they decrease rice yield, they also increase the amount of CH4 emitted per kilogram of rice. "Together, higher CO2 concentrations and warmer temperatures predicted for the end of this century will about double the amount of CH4 emitted per kilogram of rice produced.", explained Professor Chris van Kessel of the University of California in Davis and co-author of the study. "Because global demand for rice will increase further with a growing world population, our results suggest that without additional measures, the total CH4 emissions from rice agriculture will strongly increase.".

However, the authors point out that there are several options available to reduce CH4 emissions from rice agriculture. For instance, management practices such as mid-season drainage and using alternative fertilizers have been shown to reduce CH4 emissions from . Moreover, by switching to more heat tolerant rice cultivars and by adjusting sowing dates, yield declines due to temperature increases can largely be prevented, thereby reducing the effect of warming on CH4 emissions per yield. "These findings, together with our own results really stress the need for mitigation and adaptation measures to secure global food supply while at the same time keeping greenhouse gas emissions in check." van Groenigen concluded.

Explore further: Big-data analysis reveals gene sharing in mice

add to favorites email to friend print save as pdf

Related Stories

Soil microbes accelerate global warming

Jul 13, 2011

More carbon dioxide in the atmosphere causes soil to release the potent greenhouse gases methane and nitrous oxide, new research published in this week's edition of Nature reveals. "This feedback to our changing atmosphere means ...

Water-stingy agriculture reduces arsenic in rice markedly

Jul 28, 2008

A new farming method first developed to conserve precious irrigation water may have the added benefit of producing rice containing much less arsenic than rice grown using traditional rice-farming methods, researchers in the ...

Higher temperatures to slow Asian rice production

Aug 09, 2010

the world's most important crop for ensuring food security and addressing poverty—will be thwarted as temperatures increase in rice-growing areas with continued climate change, according to a new study by ...

Rice Institute calls for cuts in pesticide use

Dec 16, 2011

Rice farmers should cut the use of pesticides that kill the natural predators of the planthopper, one of the most destructive pests of the key crop, the International Rice Research Institute (IRRI) has said.

Recommended for you

Big-data analysis reveals gene sharing in mice

Dec 16, 2014

Rice University scientists have detected at least three instances of cross-species mating that likely influenced the evolutionary paths of "old world" mice, two in recent times and one in the distant past.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.