The effects of acid precipitation are as varied as they are dramatic. The harmful effects of acid rain are felt some great distances away from where the source of the problem lies. For instance, sulfur dioxides released from Midwestern power plants rise high into the air and are carried by winds toward the East Coast of the United States and Canada. “Acid lakes and streams have been found all over the country, such as in Acadia National Park on Maine’s Mount Desert Island. The lakes here are very acidic due to pollution from the Midwest.” (EPA, Air Quality and Planning Standards)
Acid rain affects the following components of the global ecosystem; soils and soil microhabitats, vegetation, aquatic ecosystems, terrestrial ecosystems, materials and buildings, visibility and human health.
Results from the National Surface Water Survey (NSWS) showed that many lakes and streams suffer from ‘chronic acidity’ a condition in which the water has constantly low pH level. “Of the lakes and streams surveyed acid rain caused acidity caused in 75 of the lakes and about 50% of the acidic streams…Several regions in the U.S. were identified as containing many of the surface waters sensitive to acidification. These include the Adirondacks and Catskill mountains in New York State, the mid-Appalachian highlands along the east coast, the upper Midwest, and the mountainous areas of the Western United States.” (EPA clean Air Markets) In addition to receiving regular doses of acidic rainfall, these areas are at risk for even more risk because they are prone to ‘episodic acidification’. This occurs when acid snow builds up over the winter months and melts in the spring. The sudden influx of acid into lakes and streams all at one, raises the levels of acid and lowers the pH rapidly causing harm to the aquatic life. This is also called ‘acid shock’.
“Acid rain causes a cascade of effects that harm or kill individual fish, reduce fish population numbers, completely eliminate fish species from a water body and decrease biodiversity.” (EPA Clean Air Market Programs) This occurs when the acid rain falls directly into the water body, reducing the pH. In addition to this however, acid rain that flows through soil in a watershed area releases aluminums. It is the combination of low pH and elevated aluminum levels that are especially toxic to the fish.
There are some species that are able to tolerate some levels of acidity, but most organisms have a specific pH range and if the pH level is too low the organisms will be unable to carry out its mist basic functions. This is partially because enzymes (biological catalysts) found in the bodies of organisms have a pH range that is optimum (See Figure 4.) Any major deviations from this will result in the denaturing of these enzymes (breaking down the protein structure) therefore the organism cannot carry out metabolic and other functions (See Figure 5.) “For instance at pH 5 most fish eggs are unable to hatch” (EPA Clean Air Market Programs.)
In an ecosystem, the organisms are highly inter-dependent. A food chain shows the feeding relationships between organisms. The base of all food chains is a producer, which is an autotrophic organism. This organism is capable of making its own food from the sun’s energy. When a first-order consumer feeds on the producer most of the energy is lost as heat, but some of it remains in the body of the consumer. Other consumers fed on the primary consumer and a biological hierarchy is formed. A combination of these food chains result in a highly complex and delicate food web. Each organism plays a vital role in this web. It has its own niche so as to reduce competition with other species.
Unfortunately, when one part of the web is destroyed this could possibly mean a collapse of the entire ecosystem. When there are high levels of acid in an aquatic environment, the producers may not be able to tolerate it, the insects that feed on the producers will loose their food source and so their numbers decline. Therefore, organisms such as frogs, that are able to tolerate relatively high levels of acidity, will have no energy passed on to them because their food supply has been eliminated.
The pollution that causes acid rain can make the air hazy or foggy, reducing visibility. This has happened in the Eastern United States for example the Great Smokies. Yet acid rain causes far more that just damage to the environment. It can create problems with human health as well. “Acid air pollution has been linked to breathing and lung problems in children and in people who have asthma. Even healthy people can have their lungs damaged by acid air pollutants.” (EPA’s Plain English Guide to the Clean Air Act.)
Acid rain can also cause economic problems if crop yields are lessened or fish harvests depleted. Humans are also affected by acid rain because it can cause damage to stone monuments or buildings (especially those made from limestone).