Lakes, streams, soil and trees continue to suffer despite the emissions cuts mandated by the 1990 Clean Air Act, according to a study by the New Hampshire-based Hubbard Brook Research Foundation.
Only deeper reductions in nitrogen oxide and sulfur dioxide emissions -- the pollutants which cause acid rain -- are likely to help the Northeast recover, scientists said in the report released Monday.
Many of the findings on acid rain damage to soil and waterways parallel those of earlier studies. The new report provides particularly strong evidence about the harm being done to red spruce and sugar maple trees.
Researchers said acid rain has contributed to a decline in red spruce trees across the eastern United States and to sugar maples in central and western Pennsylvania. Earlier reports had blamed acid rain for damage only to red spruce trees at high elevations, saying its effect on other trees was inconclusive.
Since the 1960s, more than half the canopy of red spruce trees in New York's Adirondack Mountains and Vermont's Green Mountains and one-quarter of those in New Hampshire's White Mountains have died.
The report suggested white ash and basswood trees may also be susceptible.
Supporters of federal legislation to curb nitrogen and sulfur emissions said the report was helpful to their effort.
"This is one more brick in what has become a huge wall of evidence that acid rain must be stopped as soon as possible," said Timothy Burke, executive director of The Adirondack Council, a New York-based environmental group.
The report found that 41 percent of the lakes in the Adirondacks and 15 percent of the lakes in New England have become acidic. While there have been modest improvements in the New England waterways, the Adirondacks have seen no such progress. About 24 percent of the 1,469 lakes in the Adirondacks have become too acidic to sustain fish life.
Coal-burning plants in the Ohio River Valley are cited as the major source of nitrogen and sulfur pollution that falls in the Northeast. The pollution travels eastward on prevailing winds, mixes with moisture then falls as rain, snow or fog.
For years, Northeast lawmakers have introduced legislation in Congress to cut nitrogen and sulfur emissions. But the bills have gained little support outside the Northeast and drawn strong opposition from the Midwest.
While President Bush has reversed his campaign pledge to cut carbon dioxide emissions, he has signaled he still supports reductions in nitrogen and sulfur emissions.
Scientists from Syracuse University, the University of Maine, the University of Virginia, the U.S. Geological Survey and the Environmental Protection Agency participated in the report. It will be published in the journal Bioscience.
An EPA spokesman said the agency would review the report.
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