Research links rice agriculture to global warming through methane production
carbon dioxide in the atmosphere and rising temperatures cause rice agriculture
to become a larger source of the potent greenhouse gas methane, new research
published in Nature Climate Change reveals.
results show that rice agriculture becomes less climate friendly as our
atmosphere continues to change,” said 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.
is important, because rice paddies are one of the largest human-made sources of
methane, and rice is the world’s second-most produced staple crop.”
researchers—including co-authors Bruce Hungate, professor of
biology at Northern Arizona University, and Chris van Kessel, professor at the
University of California-Davis—gathered all published research to date from 63
different experiments on rice paddies, mostly from Asia and North America.
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.
research team used a technique called meta-analysis, a statistical tool for
finding general patterns in a large body of experimental data.
strong patterns emerged when we analyzed all the data,” Hungate said. “First,
more CO2 boosted emissions of methane from rice paddies; and second, higher
temperatures caused a decline in rice yields.”
in rice paddies is produced by microscopic organisms that respire CO2, like
humans respire oxygen. More CO2 in the atmosphere makes rice plants grow
faster, and the extra plant growth supplies soil microorganisms with extra
energy, pumping up their metabolism. Increasing CO2 levels also will boost rice
yields, but to a smaller extent than methane emissions.
a result, the research found, the amount of methane emitted per kilogram of
rice yield will increase.
higher CO2 concentrations and warmer temperatures predicted for the end of this
century will about double the amount of methane emitted per kilogram of rice
produced,“ said van Kessel. “Because global demand for rice will increase
further with a growing world population, our results suggest that without
additional measures, the total methane emissions from rice agriculture will
the authors point out that there are several options available to reduce
methane emissions from rice agriculture. For instance, management practices
such as mid-season drainage and using alternative fertilizers have been shown
to reduce methane emissions from rice paddies.
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 methane emissions per yield.
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 said.
study also caught the attention of The New York Times, where it
was featured in a blog post.