Nitrogen overload concerns ecologist

San Jose Mercury News: …At Edgewood Park in Redwood City…nitrogen in vehicle exhaust from a nearby freeway has led to the local demise of a threatened butterfly population, according to research [Stuart] Weiss conducted. The link he established between the exhaust and the butterflies' decline attracted international attention among the growing federation of scientists studying "nitrogen pollution."

"I call it the biggest global change that nobody has ever heard of," Weiss said at the spring event. "The planet has never seen this much nitrogen at any time."

Human activity releases 125 million metric tons of nitrogen from agricultural activities and fossil fuel combustion a year, compared with 113 million metric tons annually from natural sources, according to a 2007 United Nations report called "Human Alteration of the Nitrogen Cycle." In 1860, the U.N. report noted, there was virtually no release from human activity. The consequences of this spike, the report added, "are profound."

Not only is the glut of nitrogen disrupting ecosystems, polluting waters and harming human health, but it's also a silent partner with carbon dioxide in changing the Earth's climate, the report said. Despite the countless initiatives under way to reduce carbon-dioxide levels to slow global warming, some scientists warn that those efforts will prove moot unless nitrogen releases also are lowered.

"We won't solve global warming without addressing nitrogen," said Elizabeth Holland, a senior scientist with the National Center for Atmospheric Research in Boulder, Colo. "The changes to the nitrogen cycle are larger in magnitude and more profound than the changes to the carbon cycle," Holland continued. "But the nitrogen cycle is being neglected."