The world of climate change science and policy has been rocked by the discovery that plants produce up to one-third of the second most important greenhouse gas. The findings are published in Nature today (12 January) by a team led by Frank Keppler from the Max-Planck Institute in Germany. Until now, researchers thought that most methane was produced by bacteria in environments lacking oxygen, such as the digestive system of cows and Asia's flooded rice fields. But Keppler's team says plants worldwide produce millions of tonnes of the gas each year, with the greatest share coming from the tropics, reports SciDev.