Atmospheric nitrous oxide concentration has increased by some 20 percent over the past century, and continues to rise at a rate of about 0.2 to 0.3 percent per year.
Beaulieu and colleagues, say the global warming potential of nitrous oxide is 300-fold greater than carbon dioxide.
Nitrous oxide accounts for some six percent of human-induced climate change, scientists estimate.
They believe that nitrous oxide is the leading human-caused threat to the atmospheric ozone layer, which protects Earth from harmful ultraviolet radiation from the Sun.
Researchers had estimated that denitrification in river networks might be a globally important source of human-derived nitrous oxide, but the process had been poorly understood, says Beaulieu, and estimates varied widely.
While more than 99 percent of denitrified nitrogen in streams is converted to the inert gas dinitrogen rather than nitrous oxide, river networks are still leading sources of global nitrous oxide emissions, according to the new results.
"Changes in agricultural and land-use practices that result in less nitrogen being delivered to streams would reduce nitrous oxide emissions from river networks," says Beaulieu.
|Contact: Cheryl Dybas|
National Science Foundation