Important new science findings show that rivers are a much higher source of greenhouse gas pollution than we had previously believed, according to a new study in the journal Proceedings of the National Academy of Sciences.
The scientists calculated that, across the globe, the waterways contribute three times the amount of nitrous oxide to the atmosphere as had been estimated by the International Panel on Climate Change (IPCC), the United Nations scientific body charged with reviewing climate change research.
They found that the amount of nitrous oxide produced in streams is related to human activities that release nitrogen into the environment, such as fertilizer use and sewage discharges.
“Human activities, including fossil fuel combustion and intensive agriculture, have increased the availability of nitrogen in the environment,” said lead author Jake Beaulieu of the University of Notre Dame and the U.S. Environmental Protection Agency in Cincinnati, Ohio.
The finding is important, the researchers say, because nitrous oxide is a potent greenhouse gas that contributes to climate change and destruction of the stratosphere’s ozone layer, which protects us from the sun’s harmful ultraviolet radiation. Compared with carbon dioxide, nitrous oxide is 300-fold more potent in terms of its warming potential, though carbon dioxide is a far more prevalent greenhouse gas. Scientists estimate nitrous oxide accounts for about 6 percent of human-induced climate change.
Beaulieu and his team measured levels in 72 streams draining multiple land-use types across the United States. When summed across the globe, the results showed rivers and streams are the source of at least 10 percent of human-caused nitrous oxide emissions to the atmosphere.
“This new global emission estimate is startling,” said Henry Gholz, a program director for the National Science Foundation’s Division of Environmental Biology, which funded the research.
Photo by: Ian Shive/The Nature Conservancy (A Conservancy researcher works in Dye Creek Preserve in the Lassen Foothills of California.)
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