forest fire

forest fire, uncontrolled fire occurring in vegetation more than 1.8 metres (6 feet) in height. These fires often reach the proportions of a major conflagration and are sometimes begun by combustion and heat from surface and ground fires. A big forest fire may crown—that is, spread rapidly through the topmost branches of the trees before involving undergrowth or the forest floor. As a result, violent blowups are common in forest fires, and they may assume the characteristics of a firestorm. See wildfire.

Though forest fire is often seen as harmful, a number of forests are specifically fire-adapted: the species of plants and animals native to those ecosystems are enhanced by or dependent on the occurrence of fire to persist and reproduce. Lightning strikes in a dry forest occur naturally, and fire can improve ecosystem health by reducing competition, fertilizing the soil with ash, and decreasing diseases and pests. Some plant species even require fire for their seeds to germinate. In many regions that have historically experienced forest fires, such as forested areas of the western United States, years of fire exclusion and suppression in the 19th and 20th centuries allowed fuels to accumulate, altering the vegetation communities present and leading to more extreme conflagrations when fires do occur. The use of prescribed fire, in which areas are burned intentionally and under controlled conditions, can restore those ecosystems and promote the conditions that were present historically prior to the removal of wildfire.