A new type of genetically modified (GM) rice might significantly lessen the impact of agriculture on the climate. The plant, equipped with DNA from barley, emits as little as 1 percent of the methane—a powerful greenhouse gas—of a conventional variety, while also producing more rice. Experts say the approach has great potential for boosting food sustainability, but requires more research to check whether the new rice performs well in paddies and fields. “They are extraordinary results,” says Timothy Searchinger, who researches climate and agriculture at Princeton University and wasn’t involved in the study.
Methane has caused roughly 20 percent of global warming since the industrial revolution. The major anthropogenic source of methane is agriculture, principally from the guts and manure of livestock and from rice. Why rice? Most of the crop is grown in flooded soil, which lacks oxygen and is an ideal home for methane-producing microbes. Between 80 percent and 90 percent of methane emitted from rice fields is produced by microbes living on plant roots; some of the gas dissolves into the water and bubbles up, but most is absorbed along with water by plant roots, travels up to the stems and leaves, and escapes into the atmosphere.
In 2002, scientists noticed that rice plants with more grain also emit less methane. The reason is that carbon locked up as starch in the rice grains (and other tissues, except roots) isn’t available to the microbes in the soil. Rice and other plants normally release carbon-rich sugars and other compounds through their roots, contributing to the soil ecosystem. These nourish beneficial microbes, but also those that make methane. In addition, microbes can use the carbon released when roots decompose.
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