cid rain in the Northeast is not just about lakes without fish, but also about forests losing their trees and soils that hoard acid before leaching it back out to contaminate local waters all over again, according to a scientific study of upstate New York and New England.
In short, the problem is more densely wound into the ecosystems it affects than scientists had previously believed, the report says — and thus harder to fight than it had appeared.
"It's a lot more complicated," said Charles T. Driscoll, a professor of environmental engineering at Syracuse University and the lead author of the study, which is to be published today in the journal BioScience.
The study, which examined data going back to the early 1960's, bolsters the conclusion already reached by many scientists that lakes and ponds in New York State and New England are not recovering from acid rain pollution. Even after 30 years of federally mandated air-emissions reductions in industry and at coal-burning power plants that are considered primary acid-rain sources, more than 40 percent of the lakes in the Adirondack Mountains at least periodically have acid levels that harm aquatic life, the study says.
Although new deposits of airborne acid compounds like sulfur dioxide and nitrogen oxides have declined, the study says that decades of acid buildup in forest soils is still being washed into waterways by erosion and spring runoff. In a paradoxical twist on environmental protection, the study found that some improvements in air quality have also proved to be a rather mixed blessing on the acid-rain front. Airborne pollutants that neutralize acid, like cement dust, partly counteract acid rain. Those pollutants are not falling into the soils in the quantities that they once did.
The report, based in part on data from the Hubbard Brook Experimental Forest in New Hampshire, comes at a time when the connections between air pollution and the nation's electricity-generating needs have become more complicated. Earlier this month, President Bush said he would oppose mandatory emissions reductions of carbon dioxide, an industrial gas most commonly linked to a different environmental problem, global warming. Mr. Bush said a mandatory reduction could hurt what he called an already stressed energy market.
Congress, meanwhile, is considering legislation that would sharply reduce the amount of acid-rain gases that power plants and other industries could discharge. States in the Northeast, including New York, have sued the owners of power plants in the Midwest, where much of the Northeast's acid-rain pollution originates. They have also asked the federal Environmental Protection Agency to issue new regulations on acid rain, with or without action by Congress.
Some environmental experts say that a confluence of forces is reviving a debate about acid rain that had been mostly quiet in recent years. There is greater public awareness of energy needs, they say, and growing evidence that past legislation to address acidic pollution in the nation's waters has not done the job.
"From our point of view, whether it's science, economic policy or politics, it's becoming more and more clear — and this report makes it more urgent — that we act this year to reduce the pollutants that cause acid rain," said Timothy J. Burke, executive director of the Adirondack Council, a conservation group in upstate New York.
Other experts say the debate is not so clear cut. Dan Riedinger, a spokesman for the Edison Electric Institute, an industry trade group that backed Mr. Bush's decision on carbon dioxide emissions, said his group would support a long-term effort to reduce the gases that cause acid rain and acid soil. But the current acid rain bills now before Congress go too far, too fast, he said.
"It's far from clear that such a drastic measure is needed to achieve a valid public policy goal," Mr. Riedinger said.
Dr. Driscoll of Syracuse said that many conclusions in the Hubbard Brook study had been reached by others. The federal Government Accounting Office, for example, concluded last year that reductions in air emissions had not cleaned up the lakes of the Northeast. But, he said, his group found evidence that acid rain was acting like a web in the northern forests, linking and compounding other problems that had seemed unrelated.
The two-year study concluded that the red spruce and the sugar maple have been hurt in different ways by acidified soils. Many tree deaths that had been attributed to things like insect infestation or drought, the study said, had in fact been hastened by acidic soil that made the trees more vulnerable.
Dr. Driscoll said that the group's research also suggested that the interplay between acid rain and global warming, though caused by different types of industrial gas pollutants, is also more complicated than had previously been believed. In particular, he said, many widely reported tree deaths in parts of the Adirondacks and New England in recent years were attributed mainly to shifts in the regional climate. The research suggests, however, that the trees were weakened first by acidified soils that made them less able to withstand climate changes.