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From the Spring 2013 Conservationist for Kids

image of a adirondack pond

What are the Effects of Acid Rain

By Gina Jack

Acid deposition affects specific components of the environment. Everything connected to them is affected as well.


image of exposed soil on a rocky mountain top
Exposed soil

Rainfall seeps into soil. It drips off tree leaves and branches to the forest floor below. The water runs across and through the soil on its way to nearby streams, rivers and lakes.

Base nutrients, including calcium and magnesium, are found in soil and are essential for plant growth. They also neutralize acids and, in a process called "buffering," help soil resist the effects of acid rain. Some soils are thin and/or have only a limited amount of these nutrients. They are not as effective at buffering acid rain as thicker soils and those rich in nutrients. Thin, nutrient-poor soils, such as those found in the Adirondack and Catskill Mountains, are especially sensitive to the effects of acid rain. Over time these soils can become increasingly acidic, reducing their ability to support healthy plant life.

Over a long period of time, soils affected by acid rain can become so acidic that aluminum, which occurs naturally in the soil, dissolves and is carried by the rainwater into lakes and streams. Dissolved aluminum is very toxic to all aquatic life.

High Mountain Areas

Areas of higher elevation, such as New York's Adirondack and Catskill mountains, are very sensitive to the effects of acid rain. Soils are thin and unable to buffer acid rain as well as areas with deeper soils. Acid fog or clouds are a problem at high elevations, too. Acids are more concentrated in this form than in rain-with a pH as low as 3-nearing the acidity of lemon juice and vinegar. When high mountain plants are damaged, they are less able to cope with the harsh weather of the region. Their growth may slow, or they may die. Plants and animals in these communities are affected when the health of their habitat declines.

hazy view from the top of a mountain
Mountain top

In the Catskills and Adirondacks, Bicknell's thrush rely upon red spruce trees for nesting and foraging. Changes to its habitat threaten the survival of this sparrow-sized bird. It is designated as a species of "Special Concern" in New York State.

Water droplets in low-lying fair weather clouds carry pollutants they have picked up from dirty air along the way. When these clouds pass over mountain tops, they surround the land like fog, depositing droplets on trees and shrubs. The water droplets often have a very low pH. Acid fog and clouds are 30% to 40% more acidic than summer rains in the same area.


image of a sugar maple with fall colors
Sugar Maple

Acid rain removes minerals and nutrients from soil that trees need to grow properly. Trees affected by acid rain are unhealthy and grow more slowly. They are weak and more likely to be damaged by cold, insects and disease. Acid on trees' leaves and needles-especially when concentrated in acid fog-wears away their protective waxy coating. When leaves are damaged, they can no longer use photosynthesis effectively to make enough food to keep a tree healthy and growing. A healthy forest provides food and shelter for many different kinds of wildlife, but an unhealthy forest does not.

Red spruce grows in mountain areas (Adirondacks, Catskills), where soils are thin and less able to neutralize acid deposition. At higher elevations, low-lying clouds can surround trees with acid fog, damaging their needles.

New York's state tree, the sugar maple, does not grow well in acidic soils. Fewer seedlings survive to maturity, and more adult trees die.

Lakes, Ponds and Streams

Most clear-water lakes and streams-water bodies that are not boggy or dark colored-naturally have a pH between 6 and 8 and support a wide variety of plants and animals. If waters become acidic, the numbers and types of fish, insects and other animals drop. The variety of plants drops, too.

Many species cannot tolerate acidic waters. Some leave and some die. The eggs of some species of fish fail to hatch. If lake water appears very clear, it may be a sign that few of the plankton (microscopic plants and animals) can survive. As water bodies stay more acidic, the variety of life they support stays low.

Melting snow combined with early spring rains can concentrate the release of a lot of pollutants into the water. Acidity increases sharply then tapers off. Aquatic life has no time to adapt to the changing conditions. In some cases, the huge volume of water in large lakes can dilute the acid. Smaller ponds and streams don't have this advantage. A "spring surge" is especially damaging for streams.

Rainwater falls directly onto lakes, ponds, rivers and streams. It also runs across and through areas (the watershed) before reaching water bodies. The soils, vegetation and human activities in a lake's watershed all influence the chemistry of the lake, including its pH.