Now there are a variety of ways to get rid of pests, depending on what kind of pests you're dealing with (or to prevent the invasion of). For a long time, the vast majority of pests, which tend to be insects as previously mentioned, have been effectively controlled through chemical means, such as trapping. What we're dealing with here is known as pesticide use. Pesticides, on the other hand, are usually very effective at controlling pests, but their environmental impact is often overlooked. It's important to remember that pesticides typically contain extremely potent chemicals. As a result, even after the pests have been exterminated, leftover traces of these chemicals are common. Those traces end up in the waterways, where they cause significant damage to the native (non-pest) plants and animals.