If conditions are conducive, the National Park Service restores animal species in parks from which they were eliminated by humans. Fire Ecology Many plant species and communities have evolved in the presence of frequent fire. Key species in such communities depend on fire for reproduction. Even the structure of plant communities, namely, the mosaics of open areas and the differing sizes and ages of plants may depend on fire. Lightening can cause natural fires.
Humans set fires accidentally but also purposely, for example, to manage a landscape.
Letting accidental fires burn and purposefully igniting fires to manage landscapes are known as prescribed burning. Prescribed burning maintains natural areas and some historic scenes. Prescribed burning must be carefully controlled to avoid endangering areas that are not amenable to fire treatment and to avoid undesirable effects such as air pollution. Many national parks provide the last remaining protected habitats for threatened and endangered species. By policy, the National Park Service also protects species that are listed by states or rare in states.