Archaeological evidence indicates that deliberate burning of forests and fields has been occurring on the North American continent for at least the past 10,000 to 20,000 years. Here are a few of the reasons native people used fire as an aid to subsistence:
- Forest Treatment. To kill insect infestations, and to diminish shrubs and grasses through which wildfire might spread, and destroy trees.
- Improve Horse Pasture. To make spring grass more easily available, and to eliminate competing species such as brush and tree seedlings.
- Improve Hunting. To thin out dense underbrush, and stimulate growth of good browse. Also used to surround deer herds to make them more accessible to hunters.
- Encourage Food Plants. To favor or increase the growth of one or more of the 200 species of plants used for food and other purposes.
- Campsite Clearing. To improve visibility and eliminate underbrush and tall grass in which attackers could hide.
- Communication. William Clark, August 31, 1805, as the Corps began the climb up to the Bitterroot Divide, wrote:
This day warm and Sultrey, Praries or open Valies on fire in Several places– The Countrey is Set on fire for the purpose of Collecting the different bands, and a Band of the Flatheads to go to the Missouri where They intend passing the winter near the Buffalow.
- Rituals. William Clark, on June 25, 1806, wrote of the three Nez Perce men who had agreed to guide them over the trail from Clearwater country to Travelers' Rest:
last evening the indians entertained us with seting the fir trees [possibly Engelmann spruce] on fire. …they have a great number of dry lims near their bodies which when set on fire creates a very suddon and immence blaze from bottom to top of those tall trees. …they are a beautifull object in this situation at night. …this exhibition reminded me of a display of fireworks. …the natives told us that their object in seting those trees on fire was to bring fair weather for our journey.
Today it is against federal and state laws to deliberately set a forest or range fire without authorization. "Prescribed burns" are carefully designed and monitored by professional foresters. Natural, lightning caused fires sometimes are allowed to burn, but are closely monitored according to a complex set of interrelated factors, including the density of underbrush and dead or fallen trees, and the proximity of sensitive resources such as structures and very young replanted trees.
Content reviewed by: Stephen F. Arno, Intermountain Fire Sciences Laboratory; Mary Horstman, Forest Historian, Bitterroot National Forest; Stan Underwood, Sula Ranger District, Bitterroot National Forest.