Excess nitrogen hurting forests, bays in Maine
Copyright © 2003 Blethen Maine Newspapers Inc.
Nitrogen pollution from vehicles, power plants and wastewater effluent is seriously damaging the health of Northeastern forests and choking oxygen from estuaries such as Casco Bay, according to a new report released Tuesday in the journal BioScience.
Nitrogen is an essential nutrient, but in large amounts it can become too much of a good thing. Too much nitrogen in the environment slows tree growth, acidifies streams, kills fish and causes algal blooms.
The report was written by a team of scientists from the Hubbard Brook Research Foundation in Hanover, N.H., a nonprofit organization that conducts scientific research to help shape public policy. It says that nitrogen pollution is cutting forest productivity by at least 9 percent a year in southern Maine and by 4 percent a year in northern Maine.
Wastewater effluent, the single greatest contributor of nitrogen pollution to Casco Bay, is not yet the overwhelming problem here that it is in more populated areas like Long Island Sound and Massachusetts Bay, the report found. But Maine's coastal waters are showing some disturbing signs they are becoming stressed.
A University of Maine professor who was part of the team that authored the report says state and federal governments are not doing enough to regulate nitrogen, despite a growing body of evidence that the pollutant is causing serious environmental problems.
"The evidence becomes more and more evident to ecologists every year that this issue isn't being addressed," said Chris Cronan, a professor of biology and ecology. "Although it may not be that well-received by the Bush administration, we're hoping that some members of Congress will put this on their agendas and start working towards it."
The researchers estimated the amount of nitrogen going into eight watersheds from Maine to New York, then evaluated several policy options for reducing the pollution.
Their study found that 36 percent of Northeastern forests are getting too much nitrogen, mostly from air pollution coming from vehicles and power plants.
That nitrogen leaches out into streamwater, Cronan explained, "and oftentimes that is accompanied by the stripping of nutrients out of the soil.
"Furthermore, that extra nitrogen coming into the streams essentially fertilizes the streams, and that can be harmful."
As many as 15 percent of the lakes and streams in New England are too acidic because of nitrogen, the scientists said, and the pollutant is killing fish in lakes throughout the Northeast.
The researchers concluded that emissions regulated by the Clean Air Act would have to be cut an additional 30 percent to stop or reverse the damage being done to the region's forests, lakes and streams.
As far as wastewater controls, "we need to find the will and the way in terms of funding to increase the use of sewage treatment processes that remove nitrogen derived from human waste," Cronan said.
While Casco Bay is still in the initial stages of nitrogen overenrichment, he said, places like Long Island Sound, where the problem is worse, show what could be in store for Maine if nothing is done.
"They have prolonged events every summer where the waters become oxygen deficient and you get shellfish die-offs," Cronan said.