Rice is the most important grain with regard to human nutrition and caloric intake in the world, providing more than one fifth of the calories consumed worldwide by the human species. Without rice and the world will be a much different place. More carbon dioxide in the atmosphere, coupled with rising temperatures, is making rice agriculture a larger source of the potent greenhouse gas methane, according to a study published in Nature Climate Change by a research team that includes a University of California, Davis, plant scientist. The authors note that relatively simple changes in rice cultivation could help reduce methane emissions.