Acid rain is a huge environmental concern, especially within the last few decades. While awareness for acid rain, and, thus, measures to combat it, tend to vary from year to year, the fact remains that acid rain is a very real threat that can eradicate entire forests. In order to gain a grasp of the extent of the destruction that acid rain causes in both the short-term and long-term, the chemical makeup of acid rain, and possible measures that can be made to prevent it, it is necessary to examine acid rain in-depth and analyze it from multiple angles from an objective standpoint.
As for the basics of acid rain; essentially, acid rain is simply normal rain that has an extremely low Ph, making it extremely acidic, although acid rain tends to differ greatly in acidity from once instance to another, acid rain is almost always a form of sulfuric acid (Likens et al 33). Acid rain tends to occur more often in the eastern part of the United States, where there tends to be the most pollution since the two primary ingredients of acid rain are sulfur dioxide and nitrogen oxide (Likens et al 33). These chemicals tend to have a snowball effect, as denser places of human urbanization and air pollution-causing factors such as vehicles and factories lead to a much greater incidence rate of acid rain.
As for the human causes of acid rain, they are actually quite numerous. For example, one source of acid rain that tends to go unnoticed by many is the generation of electricity, which entails the combustion of fossil fuels, which lead to the creation of both nitric and sulfuric acids, two key ingredients of acid rain. These two chemicals are then absorbed into the atmosphere, combining with the moisture to create the acid rain (Likens et al 34). Of course, factories and automobiles are not the only sources of acid rain. In fact, it is almost impossible for a human in today's world to not contribute negatively to the creation of acid rain in some way. This is because fossil fuels, a cornerstone of modern life, are one of the greatest offenders in terms of acid rain generation (Likens et al 33). This means that heating one's house, driving a vehicle, or even using an electronic device all contribute minutely to the creation of acid rain (Likens et al 34. Another key factor of acid rain is that it oftentimes travels for hundreds or thousands of miles from its point of original creation, meaning that acid rain created on the east coast can easily reach a long-distance across the rest of the United States, creating a large radius of potential damage (Likens et al 33-34).
Of course, humans are not the only source of acid rain, although they are, by far, the greatest contributor. There are a number of natural sources of acid rain as well. One of the most prominent of these is volcanic emissions (Park ii). These volcanic emissions tend to be extremely acidic, with pH ratings as high as 2, which causes less overall pollution to enter the atmosphere compared to human emissions, but the amount that does tends to be much more acidic (Park ii). Another common source of natural acid rain is rain itself. That is to say, even common freshwater and rainwater contains trace amounts of nitric acid, and, while the amount is minuscule, there is, naturally, a large amount of water in the world, and this causes a large amount of nitric acid to enter the atmosphere over time, occasionally causing acid rain (Park ii-iii). This causes an inverse effect to the one seen with volcanoes. Here, very trace amounts of acids are entering the atmosphere, but in a much greater overall quantity, although volcanoes are still a much greater source of acid rain than mere freshwater, even after taking into account its overall volume.
The actual effects of acid rain are profound and cause widespread damage across most areas where it is frequently observed. Perhaps one of the greatest areas that are threatened by acid rain is the surface of lakes and oceans. This is mostly because when oceans and lakes are exposed to acid rain, the overall pH level of the water lowers considerably, causing all life forms in and around the body of water to suffer as a result (Likens et al 35). These changes in pH level can easily cause a large imbalance in the natural ecosystem of a particular area, and, perhaps worst of all, there are a large number of bodies of water (especially lakes) that are exposed to acid rain. For example, one study found that New England as a whole had 15 of its lakes strongly affected by acid rain (Likens et al 35). Of these, 83 percent of them are acidic due to acid deposition, which means they were mostly caused by pollution from human sources (Likens et al 35). While New England's lakes represent a rather extreme example in terms of the overall percentage of bodies of water that are acidic, the acidity of lakes around the United States has been increasing. For example, the National Surface Water Survey found that 4.2 percent of lakes larger than 4 hectares and 2.7 percent of stream segments in acid-sensitive regions (which make up 95 percent of lakes) were acidic (Likens et al 36). This means that acid rain is a serious concern for even bodies of water, where its effects are, to the naked eye, much more difficult to perceive.
As for the effects of acid rain on the land, they are both easy to spot and detrimental to the environment. Acid rain, when it falls on forests, causes a very gradual decline of tree life, especially trees that tend to grow in higher-elevation areas, such as the Red Spruce and Sugar Maple trees (Likens et al 37). This means that, shortly after an acid rain has occurred in an area, it would be almost impossible to visually identify any real changes in the ecosystem, but over time, its effects become apparent. For example, it has been determined that acid deposition, caused by acid rain, is the cause of the deaths of about one-quarter of large canopy red spruce in the White Mountains, in New Hampshire, where acid rain tends to occur more frequently (Likens et al 37). Sugar Maple is undergoing a similar crisis, with similarly dwindling numbers. However, acid rain also makes it more difficult to re-grow these trees in the future, causing decades of problems in an affected area. Acid rain tends to be much more of a threat in high-elevation areas, where the acid rain leads to leaching of calcium from the cell membranes in spruce needles, which causes the trees to be more susceptible to freezing damage, which makes them much less tolerant to cold temperatures (Likens et al 37). Furthermore, acid rain has an effect on the soil itself as well. This is caused by microbes in the soil being killed by the increased acidity in the soil, which causes the enzymes of the microbes to be reshaped by the acidity, causing them to permanently malfunction (Likens et al 37). Acid rain also causes an increase in toxins in the soil, which brings a whole host of negative effects but does the most damage by leaching essential nutrients from other minerals (Likens et al 37).
While the effects of acid rain are undeniable and easily observable, especially over a long period of time, there are also measures that can be taken to reduce the amount of damage done by acid rain. While actually removing the harmful acids from the soil of affected areas would be extremely difficult, reducing the amount of acid rain in the first place would at least allow the damage to be lessened, and nature to eventually sort it out. This process is known as chemical recovery and is an objective process whereby there are “decreased concentrations of sulfate, nitrate, and aluminum in soils and surface waters, which lead to increased pH and acid-neutralizing capacity” (Likens et al 39). To monitor this, scientists have created five thresholds that serve as benchmarks for chemical recovery in a given region, including the historic rate of sulfur and nitrogen deposition, rate and magnitude of decreases in acid deposition, and the extent to which base cations have been depleted from the soil (Likens et al 40). However, in order to actually see these positive shifts, it is necessary to enact changes in the amount and way that humans utilize harmful substances such as fossil fuels, which are one of the leading causes of acid rain. For this reason, the advent of alternative energy, such as solar power, is probably the most concrete and effective way to slow the amount of acid rain entering the ecosystem. In addition, the amount of acid rain can be further reduced by practicing generally cleaner lifestyles, which means a greater emphasis on public transportation, recycling, and other common "green" activities. Doing this will largely remove much of the "fuel" that acid rain uses to coat large areas and ecosystems with harmful acid.
Acid rain is an issue that is often swept under the rug in favor of other environmental issues, such as global warming, but acid rain is something of a slow, gradual killer of ecosystems, and for that reason, it must be monitored extremely closely. Acid rain has a profound impact on ecosystems in a large number of areas where it is frequently observed, and these impacts are difficult to reverse. While nature does, eventually, sort out the acid rain, it is an extremely slow process. Acid rain does have the potential advantage of forcing people to adapt to a more environment-conscious style of living, especially in regards to alternative energy. The problem of acid rain, and the damage it causes, makes for compelling reasons to consider reducing the number of fossil fuels being used today. If acid rain is not dealt with, eventually its impact on ecosystems will begin to affect humanity even more than it already does, with potentially vital crops being unable to be grown. While it is impossible to eliminate the primary ingredients of acid rain altogether, they can be substantially reduced, which will help to make the planet more inhabitable for many years to come.
Likens, Gene E., F. Herbert Bormann, and Noye M. Johnson. "Acid rain." Environment: Science and Policy for Sustainable Development 14.2 (1972): 33-40.
Park, Chris C. Acid rain: Rhetoric and reality. Routledge, 2013. ii-iii.