Nitrogen overload concerns ecologist

The heavy sack, the Menlo Park ecologist explained to the small crowd gathered before him, symbolized the unprecedented release of nitrogen into the Earth's air, land and water and the insidious environmental changes the potent fertilizer is causing globally.

At Edgewood Park in Redwood City, where he stood, nitrogen in vehicle exhaust from a nearby freeway has led to the local demise of a threatened butterfly population, according to research 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."

Weiss, a Stanford University-trained scientist, researches 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.

He refers to the local demise of the bay checkerspot butterfly at Edgewood Park as "a drive-by extinction."

Reaching policy-makers 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 issue is getting the word out," she said. "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."

Nitrogen is a building block of life. Without it, plants couldn't photosynthesize, proteins couldn't form and wouldn't exist.

But it can be too much of a good thing. The mountains of nitrogen manufactured and released annually disrupt natural cycles eons in the making.

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.

With fertilizer literally falling from the sky, plants - many of them invasive weeds - get turbocharged from nitrogen, altering natural habitats by driving out native plants and the animals that rely on them.

California is at particular risk for this disruption, and the Bay Area is designated as one of the nation's hot spots for nitrogen-induced ecological shifts. Weiss estimates that in some parts of the Bay Area, auto emissions alone deliver up to 20 pounds per acre a year of nitrogen - about half the amount typically used on lawns.

The nitrogen also alters bodies of water by inducing algae growth. In Lake Tahoe, for example, algae growth is contributing to the steady loss of clarity in the lake's famously clear waters.

"We've actually found that about 55 percent of the nitrogen that gets into the lake comes from the air," said John Reuter, acting associate director of the University of California-Davis' Tahoe Environmental Research Center.

Excess nitrogen also harms human health - through contaminated water and air and by its role in increasing algae - a key food sources for disease-carrying mosquitoes.

Edgewood Park is becoming a classic example within scientific circles of nitrogen's disruptive ecological effects.

Cars whizzing by on Interstate 280 leave in their wake a trail of nitrogen. Plants absorb it, while some also settles and accumulates in the nutrient-poor soil. That extra dose of nitrogen has enabled Italian rye grass, an aggressive non-native, to drive out plantain, a favorite food of the bay checkerspot butterfly.

In 2002, nine years after the land was set aside as a preserve, the threatened butterfly disappeared from the area. (This spring, after mowing down the rye grass, Weiss and others reintroduced the butterfly to the park.)

Globally, studies cite numerous additional examples of major ecosystem shifts from nitrogen, including heathlands converting to grasslands in Europe.

Weiss advocates for better controls on nitrogen in vehicle and power plant emissions, as well as more judicious use of fertilizer.

Currently, the Environmental Protection Agency and the California Air Resources Board regulate some nitrogen compounds created during combustion but leave unregulated many other forms.

The air board takes no stance regarding evidence that nitrogen deposition is changing the state's landscape, according to spokeswoman Karen Caesar.

But many hundreds of studies support scientists' concerns about nitrogen, and Weiss said there's no other plausible explanation for why so many non-native species have taken root in nutrient-poor soil over the past two decades.

"Those of us who are studying it are pretty scared," he said.

Source: http://www.mercurynews.com/news/ci_6605545?nclick_check=1