Succession is when plants and animals move into an area and begin to change the area by bringing a new growth to it. This can begin in two different ways, but they both have the same outcome of new vegetation and life in an area. The two ways that succession can happen are through primary and secondary succession. Primary succession is when there were no plants or animals living in an area before and then species move into that new area. This is for example after a glacier moves, or lakes and rivers recede. This applies to the Great Smoky Mountains National Park mainly in areas in which the rivers have changed their path over time and now plants have moved into the areas that were formally rivers. The second kind of succession is secondary succession. Secondary succession is when an event happens that clears out an area of life, and then species begin to re-inhabit the area and change the nature of the area. This can be caused by natural disasters and natural events that cause land to be cleared. This is very common in the Great Smoky Mountains National Park, because the small forest fires begin to burn often and although they do not get out of control they still burn off the layer of underbrush, which allows for new plants to grow in their place. This is necessary for the park, because it keeps fresh plants on the forest floor as well as driving many insects into trees where they are consumed by a variety of animals, which helps the ecosystem to prosper.