Nitrogen Overdose

0 Comments | Oakland Tribune, Aug 12, 2007 | by Suzanne Bohan

ON AN OVERCAST DAY in April, Stuart Weiss stood in the rolling hills of a Bay Area nature preserve and lifted a bag of nitrogen- based fertilizer to his shoulder.

The heavy sack, the Menlo Park ecologist explained to a small crowd gathered before him, symbolized the unprecedented release of nitrogen into the Earths air, land and water, and the insidious environmental changes under way globally from the potent fertilizer.

At Edgewood Park in Redwood City where he stood, nitrogen from vehicle exhaust on a nearby freeway has led to the local demise of a threatened butterfly population, according to research Weiss conducted. The clear 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 now releases 125 million metric tons of nitrogen from agricultural activities and fossil fuel combustion a year, compared to 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 this glut of nitrogen disrupting ecosystems, polluting waters and harming human health, but its a silent partner, along with carbon dioxide, in changing the Earths climate.

Despite the countless initiatives under way to reduce CO2 levels to slow global warming, scientists warn that those efforts will prove moot unless nitrogen releases also are lowered.

One nitrogen compound is especially worrisome, as it lingers in the atmosphere for a century and is 300 times as potent a heat- trapping gas as carbon dioxide.

"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."

And that's a grave oversight, said Margaret Torn, the head of Climate Change and Carbon Management program at Lawrence Berkeley National Laboratory.

"Nitrogen should be on the radar," she said. "Unless we control that problem, we won't solve climate change."

Weiss, a Stanford University-trained scientist, focuses significant effort on researching nitrogen's far-reaching effects on ecosystems. But he also wears the hat of an advocate, pushing for more regulation of the potent element, and for greater public engagement in demanding more sustainable use of nitrogen.

To that end, Weiss eschews science-speak in addressing the public, and instead offers up memorable sound bites and photo ops, like his bag of fertilizer. He refers to the local demise of the bay checkerspot butterfly at Edgewood Park as "a drive-by extinction."

His strategy has worked, as the Edgewood Park scenario is not only referenced in scientific circles but in numerous media accounts.

Reaching policymakers and the public with an easy-to-grasp message has been one of the challenges in getting a grip on nitrogen pollution, Holland said.

"The scientific evidence for this being a problem is really accumulating," she said. "The issue is getting the word out. With the carbon cycle, you can focus on CO2. But with nitrogen, you have all these different compounds and it's a much harder story to tell."

Too much of a good thing

This element that's the focus of mounting concern is a building block of life. Without nitrogen, plants couldn't photosynthesize, proteins couldn't form, DNA wouldn't exist, and life as we know it would cease.

But too much of a good thing, especially one as potent as the mountains of nitrogen now manufactured and released annually, disrupts natural cycles eons in the making.

An inert form of nitrogen, N2, actually comprises about 80 percent of the Earth's atmosphere. It stays to itself, however, thanks to powerful chemical bonds that keep the two nitrogen molecules tightly bound.

While nature on its own does separate them and create "reactive nitrogen," it's on a limited basis. This reactive form -- which fuels life -- has historically been a scarce commodity.

But in the early 20th century, two scientists found a way to convert inert nitrogen in the air into fertilizer. The invention revolutionized agriculture, lifting limits on food production and

allowing the human population to expand exponentially.

But copious amounts of fertilizer are now used in agriculture, with the excess draining into rivers, lakes and the ocean.

Combustion of gasoline, natural gas and coal also releases enormous quantities of nitrogen-based compounds into the atmosphere, much of which settles on land and water. Animal waste is another major source of nitrogen.