Mining is a necessary process to access a large amount of different materials. However there are effects to the environment that have became more and more visible over the last few decades.
Coal mining causes a number of negative effects on the environment. Iron sulfide that is produced by coal mining connects with water and forms sulfuric acid. The acid can find its way into the waterways, and is known as acid rock drainage or acid rock damage.
Sometimes an area that is strip mined for coal will have sulfuric acid leach into the environment, that can kill plants fish and animals in the waterways. It also can cause large shifts in the pH levels.
One of the byproducts of Coal mining is Methane Gas. When released to the open air it helps cause what is known as the Greenhouse effect. Methane is believed to be responsible for about 9 percent of the greenhouse effect.
Other effects of mining can be lost of topsoil in an area. This is present in all types of mining, not just coal mining. This exposes an area to the sub surface, and results in plants and animals not being able to survive easily in areas that lack topsoil. Without topsoil vegetation will not grow, and an area ultimately dies out until new topsoil forms, this can take many years, even decades.
In some areas of coal mining, the underground coal can catch fire. Called Coal Seam fires these can burn literally for decades, and can threaten forests, buildings, roadways, towns and people.
Mining can negatively effect historical and wildlife regions, by altering the land and causing it to no longer support wildlife, birds and animals in a region. While this is something that mining companies are more aware of, it still is a concern for new and long term established mining areas.