Thirty-five years ago, the waters of Lake Colden in New York's Adirondack Mountains were found to be so acidic that they were unfit for fish life, rendering these picturesque water bodies one of the primary victims of acid rain.
The red spruce trees in New England displayed signs of stress due to the leaching of vital calcium into the soil, leading to a severe stunting of their growth. Today, the brook trout in Lake Colden have made a comeback, and the spruce trees are flourishing – tangible signs of the successful, decades-long efforts to mitigate acid rain.
Writer Ross Pomeroy explained in an article published on "Big Think" that, after significant reductions in sulfur dioxide and nitrogen oxide emissions – the culprits behind acid rain – in Europe and North America, it's easy to look back at the panicked news from the 1980s and 90s and wonder whether acid rain was, in fact, "a nuisance and not a catastrophe," as written by the honorary biochemistry professor William Reville to the Irish Times. Given our approach to handling the problem, the answer may never be definitively known.
He mentioned that U.S. scientists and their Scandinavian counterparts discovered acid rain in the 1960s and chose to gather evidence for years before raising the alarm in the 1970s and 1980s. American ecologist Gene Likens and colleagues found that while rainwater was often slightly acidic with a pH of 5.6, by 1980 the average pH level of rain in the United States had dropped to 4.6, making it about ten times more acidic, and it was getting worse.
Areas downwind from coal-fired power plants (the main sources of sulfur dioxide emissions) faced even more severe problems; the pH levels in rainstorms occasionally dropped to 3 or less, similar to grapefruit juice or soda. Such rain contributed to the erosion of buildings, depletion of nutrients needed by trees for survival and released aluminum into the soil.
The writer also highlighted that scientists across the Atlantic in Sweden warned that half of the country's lakes and rivers would reach critical acidity levels by the early mid-21st century, potentially resulting in large fish die-offs if actions weren't taken to stop acid rain.
Whether these scenarios constitute "noise," "annoyance," or "catastrophe" may depend on one's view on scientific and environmental predictions, but there is no doubt that acid rain was an escalating problem attributable to human activity.
It was for this reason, after years of public debate, that U.S. legislators established a bipartisan, commercial program, which set a cap for sulfur dioxide emissions in the energy industry at levels significantly lower than those in 1980 and allowed companies to trade emissions reductions. Limits were also placed on nitrogen oxide emissions.
This free-market program achieved outstanding success; the national average annual concentration of ambient sulfur dioxide in the United States saw an astounding 93% reduction between 1980 and 2018.
While acid rain has nearly disappeared from most parts of Europe, North America, Australia, and Japan, it remains a growing issue in places like India and China, where coal energy is still widely used. Urban areas in Latin America and Africa are also experiencing an increase in rain acidity.
For these regions, reducing the harmful emissions that fuel acid rain goes hand in hand with lowering overall air pollution levels – an important goal given that global outdoor air pollution contributes to four million premature deaths annually.
Making the air more breathable and reducing the acidity of rain benefits everyone, regardless of whether acid rain is viewed as an exaggerated or a genuine problem.
