The Harmful Effects of Acid Rain

Dead trees on at Lusen Mountain that were killed by acid rain
Trees killed by acid rain.

Ludwig Werle / Getty Images

Acid rain is a serious environmental problem occurring all over the world, particularly in large swaths of the United States and Canada. As the name suggests, it indicates precipitation that is more acidic than normal. It is harmful not only to lakes, streams, and ponds in an area but also to the plants and animals that live within the given ecosystem.

Here is what you need to know about acid rain including why it occurs and what you can do to prevent it.


Acid rain precipitation that forms when acids—typically nitric acid and sulfuric acid—are released from the atmosphere into precipitation. This causes precipitation with pH levels that are lower than normal. Acid rain is predominantly caused by humans' impact on the planet, but there are some natural sources as well.

The term acid rain is also somewhat misleading. Nitric and sulfuric acid can be transported to the Earth from rain but also via snow, sleet, hail, fog, mist, clouds, and dust clouds. 


Acid rain is caused by both human and natural sources. Natural causes include volcanoes, lightning, and decaying plant and animal matter. In the United States, fossil-fuel combustion is the primary cause of acid rain.

Burning fossil fuels such as coal, oil, and natural gas for electric power generators releases about two-thirds of all of the sulfuric dioxide and one-quarter of all of the nitrous oxide that is found in our air. Acid rain forms when these chemical pollutants react with the oxygen and water vapor in the air to form nitric acid and sulfuric acid. These acids can combine with precipitation directly over their source. But they can often follow the prevailing winds and blow hundreds of miles away before they return to the surface via acid rain.


When acid rain falls upon an ecosystem, it affects the water supply as well as the plants and animals in that area. In aquatic ecosystems, acid rain can harm fish, insects and other aquatic animals. Lowered pH levels can kill many adult fish, and most fish eggs will not hatch when the pH drops below normal. This drastically alters the biodiversity, food webs and overall well-being of the aquatic environment.

That affects many animals outside of the water, too. When fish die, there is no more food for birds such as the common loon. Acid rain has been linked to thinner eggshells in many bird species such as warblers and other songbirds. Thinner shells mean that fewer chicks will hatch and survive. Acid rain has also been found to damage frogs, salamanders and reptiles in aquatic ecosystems. 

Acid rain can be equally damaging to land-based ecosystems. For starters, it drastically changes the chemistry of the soil, lowering the pH and creating an environment where essential nutrients are leached away from the plants that need them. Plants are also directly damaged when acid rain falls on their leaves. 

In his book summarizing the research of governmental organizations, such as the Environmental Protection Agency, Don Philpott stated, "Acid rain has been implicated in forest and soil degradation in many areas of the eastern U.S., particularly high elevation forests of the Appalachian Mountains from Maine to Georgia that include areas such as the Shenandoah and Great Smoky Mountain National Parks."


The best way to reduce the incidences of acid rain is to limit the amount of sulfuric dioxide and nitrous oxide that are released into the atmosphere. Since 1990, the Environmental Protection Agency has required companies that emit these two chemicals (namely, companies that burn fossil fuels for the production of electricity,) to make major reductions in their emissions.

The EPA's Acid Rain Program was phased in from 1990 to 2010 with the final sulfuric dioxide cap set at 8.95 million tons for 2010. This is about one-half of the emissions that were emitted from the power sector in 1980. 

What Can You Do To Prevent Acid Rain?

Acid rain may feel like a huge problem, but there are actually many things that you can do as an individual to help prevent it. Any step you can take to conserve energy will reduce the amounts of fossil fuels that are burned to produce that energy, thereby reducing the formation of acid rain.

How can you conserve energy? Purchase energy-saving appliances; carpool, use public transportation, walk, or bike whenever possible; keep your thermostat low in the winter and high in the summer; insulate your house; and turn off lights, computers, and appliances when you're not using them.

View Article Sources
  1. "Effects of Acid Rain." Environmental Protection Agency.

  2. "What is Acid Rain?" Environmental Protection Agency.

  3. "Effects of Acid Rain." Environmental Protection Agency.

  4. Hames, Ralph, et al. "Adverse Effects of Acid Rain on the Distribution of the Wood Thrush Hylocichla mustelina in North America." Proceedings of the National Academy of Science, vol. 99, no. 19, 2002, 11235–11240, doi:10.1073/pnas.172700199

  5. Philpott, Don. Critical Government Documents on the Environment. Bernan Press, 2015.

  6. "Acid Rain Program." Environmental Protection Agency.

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