Fires were a part of the natural environment long before humans appeared, and many terrestrial ecosystems have adapted to it. African savana, North American grasslands, and pine forests of the southern United States are some of the fireadapted ecosystems. For example, fire helps maintain grasses as the dominant vegetation in grasslands by removing fire-sensitive hardwood trees. The influence of fire on plants became even more evident once humans appeared. ---- Indeed, humans set fires for many reasons, such as for agricultural exploitation and urban development.