Soil microbes responsible for methane emissions

Researchers have identified a group of soil-dwelling microbes that play a big role in emissions of the greenhouse gas methane in Asian rice fields.

Much of the methane produced by human activity originates in rice fields, 90 percent of which are in Asia. Until now, nobody knew which specific microbes were responsible for this process.

Yahai Lu, of the China Agricultural University, and Ralf Conrad, of the German Max-Planck-Institute for Terrestrial Microbiology exposed rice plants to radioactively labelled carbon dioxide, which the plants absorbed through their leaves, before releasing some of it from their roots into the soil.

By looking at which methane-producing organisms in the soil also contained radioactively labelled carbon, the researchers identified the "central importance" of a group of microbes known as Rice Cluster I in global methane production, reports science portal SciDev Net.

Currently, human activities release 300 to 400 million tonnes of methane each year. Their contribution to global warming is equivalent to one-third of that made by man-made carbon dioxide emissions.

Rice fields emit between 50 and 100 million tonnes of methane each year.

Methane is the most important greenhouse gas, after carbon dioxide. Although more carbon dioxide is emitted, methane is thought to be 20 times more effective at trapping heat in the atmosphere.