Nitrogen Harming Northeast Forests and Waters

By J.R. Pegg

WASHINGTON, DC, April 16, 2003 (ENS) - Nitrogen pollution is widespread in the ecosystems of the Northeastern United States and current policies will do little to change the situation, finds a new two year study coordinated by the Hubbard Brook Research Foundation.

Excess nitrogen in the environment degrades air quality, disrupts forest growth, acidifies lakes and streams and starves coastal waters of oxygen.

The study "Nitrogen Pollution in the Northeastern United States: Sources, Effects and Management Options," published in the April issue of the journal "Bioscience," pulls together a range of data on the effects of nitrogen pollution on forests and watersheds in the Northeast.

Although the team of 12 scientists does not advance specific policy options, they are clear in the belief that the current regulatory regime to reduce nitrogen pollution is failing to make a significant dent in a growing problem. forest

Remote Northeastern forests are affected by nitrogen emissions from as far away as the Midwest United States. (Photo courtesy Syracuse University)
Airborne emissions of nitrogen and nitrogen discharged from wastewater treatment plants were far and away the dominant sources of nitrogen pollution to forests and coastal waters studied by the research team.

Nitrogen in wastewater discharge is a simple reflection of the high nitrogen content in many American diets and the inability - or unwillingness - of policymakers and industry to install technology that could remove much of this nitrogen from wastewater before it is released.

Airborne emissions come primarily from vehicles and power plants, but current laws do not go far enough to remedy this growing concern according to the study's authors.

"Little progress has been made in reducing total emissions of nitrogen," said lead author Charles Driscoll, a Syracuse University environmental systems engineering professor.

"So unfortunately, we were not surprised that airborne nitrogen pollution continues to be a serious problem for Northeast forests and streams."

Analysis in the report indicates that additional reductions in total nitrogen emissions of 30 percent or more would be needed to reduce nitrogen runoff to less harmful levels.

The report details findings from analysis of eight Northeast watersheds and two smaller, forested watersheds. Although the watersheds analyzed in the report all suffer from nitrogen pollution, they are affected to varying degrees by different sources.

Large populated watersheds are most impacted by nitrogen discharges from wastewater treatment plants, followed by atmospheric emissions from vehicles and power plants, and finally by agricultural runoff of nitrogen rich fertilizers. estuary

Estuaries are in particular affected by nitrogen heavy wastewater. (Photo courtesy
But nitrogen in food, which ends up in sewage wastewater, is the largest source of reactive nitrogen in most of the watersheds in the study.

Coastal estuaries feel the brunt of nitrogen pollution in these watersheds, as wastewater discharge collects downstream, directly affecting these ecosystems.

At least 14 major estuaries in the Northeast have been classified as "highly impacted" due to elevated nitrogen levels, which have contributed to the loss of seagrass beds, increase algal blooms, reduced biodiversity and fish kills due to oxygen depletion.

But there are policy prescriptions that could begin to reverse the effects of nitrogen pollution.

"Improved wastewater treatment is the single most effective means of reducing nitrogen pollution in coastal waters of the Northeast," said Mark Castro, an associate professor at the University of Maryland.

The technology to cull some two thirds of the nitrogen that accumulates in wastewater exists, said coauthor and coastal ecologist David Whitall, but funds have not been earmarked to widely deploy it.

The U.S. Environmental Protection Agency estimates there is a $30 billion gap in clean water financing needed to address nitrogen and other water quality issues.

"Treating wastewater produces the largest reduction," Whitall said, "but an integrated scenario that also targets airborne emissions nets the largest result."

Airborne emissions of nitrogen from vehicles and power plants, along with agricultural runoff, are the main sources of nitrogen pollution impacting the remote forests of New England.

The issue of nitrogen pollution in forest can be a bit tricky, the researchers explain, because initial inputs of nitrogen can increase forest productivity. But excessive nitrogen can damage soil, reduce tree growth and produce acidic nitrate runoff to streams.

Of particular interest is the report's finding of nitrogen pollution in the Hubbard Brook Experimental Forest, a 7,800 acre research area within New Hampshire's White Mountain National Forest. The area was set aside for hydrologic research in 1955 and is a key part of one of the longest running ecosystem studies in the world.

Analysis of the past 40 years at the Hubbard Brook Experimental Forest shows that nitrogen pollution deposited on Northeast forests has not decreased since the 1960s.

The authors report that 36 percent of the forestland in the Northeast has nitrogen deposition rates in excess of eight kilograms of nitrogen per hectare, the rate at which elevated nitrate runoff occurs in forests. bulldozer

Agricultural runoff of nitrogen rich fertilizer can scar the land and pollute the water. (Photo by Jack Dykinga courtesy Agricultural Research Service)
This nitrate forest runoff is a leading contributor to the acidification of lakes and streams and the study found it is affecting 41 percent of lakes and streams in the Adirondack region of New York and 15 percent of lakes and streams across New England. The greater impact in the Adirondacks is in part because of the area's higher elevation and greater exposure to airborne emissions.

The effects of nitrogen pollution do not just harm forests and watersheds, the researchers note. Nitrogen emissions are the primary source of ground level ozone, which is considered harmful to forest production and to human health. Some 26 million Americans in the Northeast are exposed to high ozone levels each year.

The report's authors hope the findings in the two year study will prompt policymakers to aggressively target nitrogen pollution, but they note that different regions will need different policies.

For example, the Chesapeake Bay in the mid-Atlantic region of the United States has a serious nitrogen pollution problem, but agriculture is a much larger source of nitrogen for this water body than it is for many in the Northeast. And different soils absorb nitrogen at different rates, so regional policies and a multi pronged approach is warranted, the study's authors say.

Even aggressive action will take time to restore the health of ecosystems affected by nitrogen pollution.

Analysis of the Biscuit Brook watershed in New York's Adirondack Mountains found that when cuts in sulfur dioxide emissions from electric utilities at levels of 75 percent more than the current law are considered with nitrogen reductions, the watershed would only reach near full chemical recovery by 2050.

"The best way to achieve nitrogen reduction is to target multiple sources in our management strategy," said Driscoll. "And if we want to deal with this problem, we have to discuss an integrated nitrogen management strategy."