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Ominous dark clouds over a bright green forest

The term acid rain evokes images of dissolving vegetation and wildlife, burning skin, and a hazy, destructive atmosphere.

In reality, the effects of acid rain are not that extreme, but it remains a troublesome and harmful phenomenon, the causes of which can largely be traced to societal activities.

Liquids with a pH of less than 7 are considered acidic, those above 7 are alkaline. While pure water has a perfectly neutral pH of exactly 7, rain water reacts naturally with carbon dioxide in the atmosphere to form carbonic acid and has a slightly acidic pH.

Fossil fuels like coal, natural gas, and oil are burned as energy and electricity sources.  Unfortunately, they also result in emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx). These pollutants rise into the atmosphere where they react with various elements and are converted into sulfuric acid and nitric acid, respectively. In industrialized areas, pH readings below 2.4 (equal to the acidity of vinegar) have been recorded.

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The term “acid rain” dates back to 1872, but its effects were not studied in-depth until the late 1960s. When the acids are removed from the atmosphere and deposited on various Earth surfaces in the form of rain, sleet and snow; they have insidious effects on the ecosystems they enter. In freshwater lakes and streams, lower pH levels resulting from acid rain leave most fish eggs unable to hatch. In extreme cases, acidic lakes and river can kill adult fish as well.

Acidic precipitation can alter soil chemistry by leaching away essential nutrients like calcium and magnesium. This in turn limits the nutrients available to trees and other vegetation. In combination with other environmental stressors like pollution, insect infestation, drought, and disease, acid rain can kill trees and ruin forests. High altitude forests, which are often blanketed in acidic clouds and fog, are particularly vulnerable. Farmers routinely resort to fertilization techniques to replace the lost nutrients in soil and occasionally use crushed limestone to act as a buffer against acidity as well.

The good news is that legislation passed in the 1980s and 1990s has successfully reduced SO2 emissions by 40% in the last 25 years. Nitrogen oxides emissions from cars have been greatly reduced due to technological advances like catalytic converters in exhaust systems. Individuals can do their part with simple measures like turning off lights, carpooling, and recycling. Focusing our efforts and encouraging our friends to do the same can minimize the amount of dangerous pollutants released into Earth’s atmosphere. Click here for more information on ways you can help reduce damage caused by acid rain.