Forest fires and healthy forests

Forest fires can be natural or caused by humans. They destroy life and property and devastate thousands of hectares, but they are also vital to the health of the forest.

Background

Evidence of forest fires is routinely found in soil samples and tree borings. The first major North American fires in the historical record were the Miramichi and Piscataquis fires of 1825. Together, they burned more than 1 million hectares in Maine and New Brunswick. Other U.S. fires of significance were the Peshtigo fire in 1871, which raged over 500,000 hectares and took fourteen hundred lives in Wisconsin; the fire that devastated northern Idaho and northwestern Montana in 1910 and killed at least seventy-nine firefighters; a series of fires that joined forces to sweep across a third of Yellowstone National Park in 1988; and the “Station Fire” of 2009, the largest in the history of Los Angeles County. In the second and third decades of the twenty-first century, California and other western and northwestern states were ravaged by fires, including the 2018 Camp Fire, the 2020 Bay Area Fire, and the 2021 Dixie Fire.

Fire Behavior

Fires need heat, fuel, and oxygen. They spread horizontally by igniting particles at their edge. At first, flames burn at one point, then move outward, accumulating enough heat to keep burning on their own. Topography and affect fire behavior. Fires go uphill faster than downhill because warm air rises and preheats the uphill fuels. Vegetation on south- and west-facing slopes receives more sunlight and so is drier and burns more easily. Steep, narrow canyons will pull heat up them like a chimney, increasing heat intensity.

For several reasons, only one-third of the vegetation within a large fire usually burns. This mosaic effect may be caused by varied tree species that burn differently, old burns that stop fire, strong winds that blow the fire to the leeward side of trees, and varied fuel moisture.

Forest Management

One of the early criteria of forest management was fire protection. In the second quarter of the twentieth century, lookout towers, firebreaks, and trails were built to locate fires as quickly as possible. Low fires that typically would have burned through the forest at ground level and cleared out brush every five to twenty-five years were suppressed. As a result, the natural cycle of frequent fires moving through an area was broken. Fallen trees, needles, cones, and other debris collected as kindling on the forest floor rather than being incinerated every few years.

It took foresters and ecologists fifty years to realize that too much fire suppression was as bad as too little. Accumulated kindling burns hot and fast and explodes into treetops. The result is a devastating crown fire, a large fire that advances as a single front. Burning embers of seed cones, as well as sparks borne by hot, strong winds created within the fire, are tossed into unburned areas to start more fires.

In the 1970s, prescribed burning was added to forest management techniques used to keep forests healthy. Fires set by lightning are allowed to burn when the weather is cool, the area isolated, and the risk of the fire exploding into a major fire low. More than 70 percent of prescribed burning takes place in the southeastern states, where natural fires would burn through an area more frequently than in the West.

Causes of Fires

Forest fires may be caused by natural events or human activity. Most natural fires are started by lightning strikes. Dozens of strikes can be recorded from one lightning storm. When a strike seems likely, fire spotters watch for columns of smoke, and small spotter planes will fly over the area looking for smoke. Many of the small fires simply smolder and go out, but if the forest is dry because of drought or any period of hot, dry weather, multiple fires can erupt from a single lightning storm.

The majority of forest fires are human-caused, and most are the result of carelessness rather than arson. Careless campers may leave a campsite without squelching their campfire completely, and winds may then whip the glowing embers into flames; a smoker may toss a cigarette butt from a car window; sparks from a flat tire riding on the hub may set fire to vegetation alongside the highway; and the sun shining through a piece of broken glass left by litterers may ignite dry leaves.

Prescribed fires may be natural or human-caused. In some areas, they are set in an attempt to re-create the natural sequence of fire, as in Florida, where prescribed burns provide wildlife habitat and open up groves to encourage healthy growth. Other prescribed fires start accidentally but are allowed to burn until they reach a predetermined size.

Benefits of Fire

Some tree species require very high temperatures for their seed casings to split for germination. When fire periodically sweeps through the forest, seeds will germinate. Other species, such as the fire-resistant ponderosa pine, require a shallow layer of decaying vegetable matter in which to root. Fires burn excess debris and small trees of competing species, leaving an open environment suitable for germination. Dead material on the forest floor is processed into nutrients more quickly by fire than by decay, and in a layer of rich soil, plants will sprout within days to replace those destroyed in the fire, thus providing feed for wildlife.

Fire intervals vary. Without human intervention, spacious ponderosa pine forests will burn every five to twenty-five years. Lodgepole pine, which grows in dense stands, will burn every two hundred to four hundred years. Southern pines, if fire is not suppressed, are cleared every three to five years.

Disadvantages

Erosion is one of the devastating effects of a fire. If the fuels burn hot, tree oils and resins can be baked into the soil, creating a hard shell that will not absorb water. When it rains, the water runoff gathers mud and debris, creating flash floods and extreme stream sedimentation. Culverts and storm drains fill with silt, and streams flood and change course. Fish habitat is destroyed, vegetation sheltering stream banks is ripped away, and property many kilometers downstream from the forest is affected.

When a fire passes through timber, it generally leaves pockets of green, although weakened, stands. Forest pests such as the bark beetle are attracted to the burned trees and soon move to the surviving trees, weakening them further and destroying them. Healthy trees outside the burn area may also fall to pest infestation unless the burned trees are salvaged before pests can take hold. The ash and smoke from hot, fast-burning forest fires can be transported for kilometers, affecting the air quality of cities many kilometers from the actual fire.

Relationship to Timber Resources

Although a prescribed fire is an attempt to duplicate natural fire, it is not as efficient because private and commercial property within the fire path must be protected. Once a fire has occurred, burned timber deteriorates quickly through either insect infestation or blue stain, a fungus that stains the wood. Private landowners can move quickly to salvage fire-damaged trees and plant new seedlings to harness erosion. On federal land, regulations governing the salvage of trees can delay logging of the burned snags until deterioration makes it uneconomical to harvest them.

Fire Fighting

Bulldozers are used to cut fire lines ahead of the approaching fire, and fuels between this line and the fire are backburned. Helicopters and tanker planes drop water with a fire-retardant additive or bentonite, a clay, at the head of the fire to smother fuels. Firefighters are equipped with fire shelters in the form of aluminized pup tents, which they can pull over themselves if a fire outruns them. Despite technological advances, one of the best tools for fighting fires—along with the shovel—remains the Pulaski, a combination ax and hoe, first produced commercially in 1920. This tool, in the hands of on-the-ground firefighters, is used to cut firebreaks and to throw dirt on smoldering debris.

Public Policy and Public Awareness

Beginning in the early twentieth century, forest fires engendered public policy. In the aftermath of major fires in 1903 and 1908 in Maine and New York, state fire organizations and private timber protective associations were formed to provide fire protection. These, in turn, contributed to the Weeks Act of 1911, which permitted cooperative fire protection between federal and state governments.

People who make their homes in woodland settings in or near forests face the danger of forest fire, and government agencies provide information to help the public safeguard themselves and their property. Homes near forests should be designed and landscaped with fire safety in mind, using fire-resistant, noncombustible materials on the roof and exterior. Landscaping should include a clear safety zone around the house, and hardwood trees, less flammable than conifers, should be planted.

In June 2015, Representative Bruce Westerman, a Republican from Arkansas, introduced the Resilient Federal Forests Act of 2015, which became known as the Emergency Wildfire and Forest Management Act of 2016. The bill is intended to expedite forest management activities related to forest fires and other natural catastrophes on federally held lands, make it harder for plaintiffs to sue the United States Department of Agriculture Forest Service, and decrease the influence of governmental and environmental activist organizations. Proponents of the bill, such as the National Association of State Foresters, said the bill would help fix a broken funding system for forest management and fire response. Critics of the bill, including the Wilderness Society and congressional Democrats, said that it would empower corporations at the expense of citizen participation and oversight by limiting public debate on federally managed commercial logging projects. The bill was amended and passed the House in July 2015 before being sent to the Senate. In 2021, Senators Diane Feinstein, Alex Padillo, Ron Wyden, and Congressman Jimmy Panetta introduced the Wildfire Emergency Act, to provide federal funds for forest restoration projects, critical infrastructure, energy flexibility, research and training, and for disadvantaged communities. The act remained in committee in 2023.

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