By Carolyn Csanyi
Updated Aug 30, 2022
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Acid rain became a major environmental concern with the industrial age’s widespread combustion of fossil fuels. While naturally occurring acid rain exists, the release of sulfur dioxide and nitrogen oxides from coal and oil power plants reacts with precipitation to form sulfuric and nitric acids that erode ecosystems. The U.S. East Coast—including the Appalachian Mountains and the Northeast—suffers the greatest damage.
A National Surface Water Survey found that acid deposition has rendered 75 % of the nation’s lakes acidic and 50 % of streams. The highest concentrations appear along the Atlantic coast, where waters already have elevated acidity. In the New Jersey Pine Barrens, more than 90 % of streams exceed acidification thresholds. Little Echo Pond in Franklin, New York, recorded a pH of 4.2, among the lowest in the country.
Acid rain leaches essential soil nutrients such as calcium and magnesium, which normally buffer acidity and support plant growth. The loss of these ions weakens trees, making them more vulnerable to disease, pests, drought, and cold. Acidification also mobilizes dissolved aluminum, which can be toxic to aquatic life. Appalachian forests from Maine to Georgia are particularly susceptible. While individual trees rarely die outright, cumulative stress reduces forest resilience. The U.S. Environmental Protection Agency’s Acid Rain Program, which has cut sulfur dioxide emissions by more than 80 %, is expected to alleviate acidification along the East Coast over the coming decades.
