Controlled burning
Controlled burning, also known as prescribed burning, is the intentional setting of fire for specific ecological and management purposes. This practice is primarily employed in forest management to mitigate the threat of larger, uncontrollable wildfires by reducing excess fuel on forest floors, which can accumulate over time. Controlled burns benefit ecosystems by promoting new plant growth, aiding in the germination of certain seeds, and maintaining diverse habitats for various animal species. For example, some tree species, like the giant sequoia and lodgepole pine, rely on the heat from fires to release their seeds effectively.
In agriculture, controlled burning has historical roots in practices such as slash-and-burn farming, which clears land and enriches soil by returning nutrients. Modern agricultural applications include the use of fire to eliminate weeds, pests, and competing plants, thus enhancing crop production. The technique is also beneficial in managing rangelands, where controlled burns are used to promote nutritious grass growth for grazing animals like bison.
While controlled burning offers various ecological advantages, it is essential to recognize that it can also have negative environmental impacts, such as air pollution and potential soil depletion. Therefore, its use requires careful planning and consideration within the broader context of land management and conservation.
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Controlled burning
DEFINITION: Intentional setting of a fire to accomplish a specific purpose
The controlled use of fire can benefit forests by preventing larger, uncontrollable wildfires and by removing undesirable plants, promoting certain animal species, and stimulating the germination of some seeds; controlled burns are also used as a means of fighting wildfires. The controlled burning used in agriculture, however, is often accompanied by negative environmental impacts such as air pollution and eventual soil depletion.
Controlled burning, also called prescribed burning, is one tool that foresters use to help contain wildfires. There are three ways to extinguish a fire: Cool the fuel below its kindling temperature, deprive the fire of oxygen, or deprive the fire of fuel. Pouring water on a fire addresses the first two of these; the setting of a controlled burn known as a backfire is one way to accomplish the third. If the wind is blowing toward a raging wildfire, firefighters may set a line of fire in front of the wildfire. When correctly controlled, the backfire consumes the available fuel before the wildfire can reach that area; the wildfire then dies out for lack of fuel.
Controlled burning is also used as a way of preventing large, unmanageable wildfires. In forests and other wilderness areas, lightning strikes start many fires every year, and nature has adapted to relatively frequent burning. Fires promote new growth and renewal of a forest in several ways. For example, cones from the giant sequoia and the lodgepole pine do not their seeds unless they have been dried or heated, and heating is more efficient. Fires clear the ground of brush, leaves, pine needles, and dead wood, allowing seeds to sprout in the ground, which is moist and enriched by nutrients leached from the ashes. (Forest floor litter dries out more quickly than the soil underneath, and seedlings that sprout in the litter generally die.) In addition, fire burns away plants that would have blocked sunlight from seedlings.
If too much time elapses between fires, however, fuel can accumulate to dangerous levels on the forest floor. When a fire starts after a long period of fuel accumulation, it is likely to burn so hot that standing trees will be consumed, and in a strong wind, flames will jump from the crown of one tree to the crown of the next. Crown fires race quickly through a forest and are very difficult to extinguish. Foresters have come to understand that it can be far less destructive to a forest to use controlled burns to keep the fuel load at a safe level.
Other uses of controlled burning are found in agriculture. After the last ice age, about 11,000 years ago, hunter-gatherers settled down to farming and adopted the slash-and-burn technique for clearing land. Large trees were cut down, and smaller trees and underbrush were burned; this both cleared the land and released nutrients into the soil. After a few years, when the land began producing less, a new area was selected and the cycle repeated. This practice continues in some parts of the world in the twenty-first century, notably in the Amazon rain forest and in Southeast Asia. In the United States, some Oregon grass-seed farmers use fire to kill competing weeds, weed seeds, insects, and rodents because burning is cheaper than other methods and is more effective on steep terrain. Oklahoma wheat farmers burn wheat stubble for similar reasons.
Range managers in the Wichita Mountains Wildlife Refuge have adopted the controlled burning practice known as patch burning. They set controlled fires in areas of rangeland from 40 hectares (100 acres) to 8,100 hectares (20,000 acres) in size every few years to provide the bison in the refuge with the nutritious, tender grass shoots that grow in the burned areas. Fuel is allowed to accumulate in unburned areas, which are then burned to repeat the cycle.
Bibliography
Booker, Christopher and Weber, Sam. "Communities Are Embracing 'Controlled Burns' to Protect Themselves." PBS, 27 Mar. 2022, www.pbs.org/newshour/show/communities-are-embracing-controlled-burns-to-protect-themselves. Accessed 15 July 2024.
Carle, David. Introduction to Fire in California. Berkeley: University of California Press, 2008.
"Controlled Burning." National Geographic, education.nationalgeographic.org/resource/controlled-burning/. Accessed 15 July 2024.
Reinhart, Karen Wildung. Yellowstone’s Rebirth by Fire: Rising from the Ashes of the 1988 Wildfires. Helena, Mont.: Farcountry Press, 2008.
Ribe, Tom. Inferno by Committee: A History of the Cerro Grande (Los Alamos) Fire, America’s Worst Prescribed Fire Disaster. Victoria, B.C.: Trafford, 2010.