Increases in acidity by 1 pH unit in the Adirondack lakes of New York—changes that normally occur over hundreds or thousands of years—occurred during 2 to 4 decades in some New York lakes in the middle of this century, according to a study released March 14, 1986, by a committee of the National Research Council (NRC). On the basis of their analyses, the Committee on Monitoring and Assessment of Trends in Acid Deposition concluded that there is a cause and effect relationship between sulfur emissions produced by the burning of fossil fuels and acid rain.

At the same time, the committee found that “lake acidification is not a uniform problem,” according to committee chairman James H. Gibson. Individual lakes vary widely in their responses to acid deposition, and some of the northeastern U.S. lakes that the committee studied have even become more alkaline in recent decades, said Gibson, who is coordinator of the National Resources Ecology Laboratory at Colorado State University in Fort Collins. “Differences in the geologies of watersheds and in the histories of land use practices within watersheds can cause surface waters in a region to respond differently even when they are receiving equivalent amounts of acidity from atmospheric inputs,” the report said.