A study led by U-Minnesota scientists says emissions of nitrous oxide, a greenhouse gas, from Midwest streams may be much larger than thought. “Agriculture, and specifically nitrogen fertilizers used in row-crop farming, is a major contributor to nitrous oxide emissions from streams,” says U-Minnesota, based on the research paper. Emissions may have been underestimated by as much as 40 percent. The smallest streams had the highest rates of emissions, possibly a result, researchers say, of high nitrogen loading and higher turbulent exchange rates.
The findings suggest that a U.N. panel looking into climate change is too conservative in its figures for emissions from waterways in agricultural areas. One of the authors of the study, Peter Turner, says rivers have been overlooked as a source of nitrous oxide because of the great variability in stream size and land use. The next step is to study nitrous oxide degassing in waterways in regions where use of nitrogen fertilizer is high, such as China and India.