It started in the mid 1800s as nothing more than an oddity that would, in the 20th Century, become a scourge requiring world cooperation to overcome. The industrial revolution provided the world's population with a previously unattainble quality of life. But it also created rain that was slightly more acidic than the world had previously experienced. Over the coming decades, this academic curiosity would become a plague that would wipe out entire European forests and threaten streams and lakes in North America. The cause was quickly noted, but only in recent years has the table started to turn.
Acid rain is caused by sulfur dioxide and nitrogen oxides. The largest emitter of these compounds are coal power plants. As these chemical compounds are emitted from smokestacks around the world, the pollutants are released into the atmosphere where they mix and bond with water vapor. This changes the pH balance of the vapor and when becomes slightly acidic when it falls as rain.
This can be highly destructive to plants and some animals. Though humans are not directly affected by acid rain, plants and animals we depend on can be affected by the situation. If left unchecked, this can create disruptions in the food chain and adversely affect the economy.
In forests, acid rain carries out a two-pronged attack on trees and other vegetation, one from below and one from above. Though some microbes can accommodate a lower pH level in the soil (and some even thrive in it) the areas that are most adversely affected by acid rain have no such microbes. As those microbes die off, nutrients in the soil are not replenished, severely stressing out the vegetation that depends on the health soil. As rain and fog envelop trees from above, the trees outer growth, such as the bark and leaves, are further put under difficulty.
Waterways can also be adversely affected by acid rain. Many fish and insects need very particular pH levels in order to reproduce. If no new generations replace the old ones, the fish eventually die off. The few fish that are left are put in further jeopardy by lack of insects and larvae, which are a major food source. In the United States, acid rain has been blamed for the reduction of brook trout, according to the United States Environmental Protection Agency.
While there has been years of damage, there is also a fair amount of good news. As new technology has been developing, coal-fired power plants have become cleaner. Scrubbers now can remove more than 95 percent of the sulfur that used to go into the atmosphere. Some power plants can be retrofitted for this technology, while others cannot.
But efforts to reduce sulfur and other harmful compounds have already been successful. In the Appalachians, there has already been reports of reduced acid rain. This has led to a significant recovery of plants and animals in those areas. Streams are becoming healthier, according to scientists who have been testing some of them monthly for nearly 20 years.
In short, acid rain, unlike some other environmental problems such as global warming, is one that actually can be solved rather easily. The technology is already there and being implemented and the effects can be reversed in years, not decades or centuries. But without continued supervision and work on the problem, acid rain could, once again, become a major problem.