Report: Acid rain impact remains a concern

Acid rain dissolves forest nutrients much faster than previously believed, posing a threat to future forest productivity, according to a study

In this story: Acid rain has long history Long-term research used RELATED STORIES, SITES

WOODSTOCK, New Hampshire (CNN) -- A new study on acid rain concludes that, while some affected areas have seen improvement, the impact of emissions may be much more complicated than previously understood.

The study, led by Charles Driscoll of Syracuse University, found that despite major progress in decreasing U.S. emissions of acid rain-producing chemicals, 40 percent of the lakes and streams in New England and upstate New York continue to occasionally post acidity levels that harm plant and animal life. Fifteen percent of those waterways still have chronically high acid levels.

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Environmental issues

Acid precipitation -- carried to earth in rainfall, snow, or fog -- is a byproduct of the burning of fossil fuels. Airborne compounds like sulfur dioxide and nitrogen oxides alter the chemical balance of soils and waterways, turning them from chemically neutral to acidic.

In the United States, the Clean Air Act has tightened the rules on acid rain-related emissions -- now roughly 62 percent of their peak levels in the 1970s. Congress is considering further tightening of acid rain-related regulations.

But threats remain to fish and tree populations in areas affected by acid rain, according to the report. Original research prepared for the study suggests that acid rain may weaken plant life in a way that provides the knockout punch for species like red spruce and sugar maple trees.

Acid rain has long history

Vegetation already under stress from a variety of other pressures -- insect infestation, drought, climate change, and more -- may suffer cumulative damage from exposure to acidified soils. Of particular interest in the study area are the sugar maples.

A backbone of commerce in northern New Hampshire and Vermont, the trees that produce maple syrup are already predicted to be endangered by a warming climate.

Acid rain, first identified as an environmental risk in 1872, was not recognized as a major environmental problem until more than a century later.

Reports of sterile lakes and dying forests in eastern North America, Scandinavia, Germany, Poland and Russia were linked to high acidity levels in waterways and soils.

Those acid levels were in turn traced to airborne, highly acidic chemicals like sulfur dioxide, emitted from smokestacks through the burning of fossil fuels. Coal with high sulfur content, used to fuel factories and electric-generating stations, was identified by researchers as the leading contributor.

Ironically, local pollution concerns near factories and power plants helped spread the acid rain problem. Political pressure forced many coal-burning facilities to build extremely high smokestacks -- reducing serious pollution problems near the plants, but enabling the acid rain chemicals to be transported hundreds, or even thousands, of miles away from the source.

Coal-burning power plants in the Ohio River Valley, for example, are cited as a major source of the acid rain problems in New England and eastern Canada.

Long-term research used

The study relied on a compilation of many long-term acid rain research projects, as well as original research from the New Hampshire-based Hubbard Brook Research Foundation, which is affiliated with the University of New Hampshire.

The study will be published in the March issue of the journal BioScience.

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Syracuse University
University of New Hampshire

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