Home->Summer 2002

Are there good forest fires?

Yes there are good forest fires. In fact, foresters often “prescribe” fire to dispose of accumulated debris, enrich the soil by speeding nutrient recycling or retard the growth of shrubs or grasses that would otherwise crowd out recently planted seedlings.

But prescribed fire is not wildfire. Moreover, as we’ve already explained, the wildfires that are burning in the Southwest today are burning well beyond the parameters for which scientists can find observable evidence of past behavior: fire scars on stumps, ash accumulations in soil and the presence or absence of woody debris.

Historically, fires burned frequently in the Southwest—on three-year intervals in some places, a bit less frequently in others, every ten years on average in ponderosa pine and low elevation Douglas-fir forests. Because they traveled close to the ground, most of these fires were not very intense. But they did help enrich the soil by hastening the release of nutrients stored in dry grass, shrubs, seedlings, fallen trees and decomposing plant matter.

By contrast, the crown fires that now frequent the Southwest don’t have any redeeming value. In fact, their ferocity is difficult to comprehend: flames moving fast enough to overrun birds in flight, burning hot enough to crack boulders, melting topsoil’s organic layer into a waxy glaze that is impervious to water. The flooding that follows often strips stream channels to bedrock, washing away every vestige of fish habitat.

So the irony: our early attempts to contain wildfire—a societal decision made some 80 years ago— simply postponed the unexpected but inevitable return of even larger fires and more destructive fires. Worst yet, millions of people now live in or near in or near forests, often unaware of the danger they face. In the Southwest alone, the Forest Service estimates 200,000 homes are at risk because of their proximity to national forests with a high burn probability.

Of course, forests eventually recover from the ravages of wildfire, no matter how catastrophic the damage. But healing often takes hundreds of years—a fact that could permanently cripple every industry in the Southwest, especially if forested watersheds stop functioning.

Getting along with nature is challenging, especially in a modern society that is so dependent on the steady flow of goods and services the earth provides. How easily we forget that all natural systems— including forests and woodlands— perpetuate themselves through disturbance: wind, floods, insects, diseases, earthquakes, ice storms, volcanic eruptions, lightning and wildfires. Nature passes no judgements as to the good or evil that these disturbances unleash. They simply are. They do what they do. Things change, sometimes subtly, sometimes suddenly. Old forests perish and new ones take their places. Time marches on.

Much of the chaos that is nature goes on unnoticed—nitrogen fixation for example. By volume, colorless odorless nitrogen makes up 80 percent of the earth’s atmosphere. It also exists in nitrogeneous compounds present in plant and animal tissues, especially proteins. Nitrogen is a marvelous fertilizer, but to do its work it must first be fixed—combined with other elements by biological or chemical action to form compounds green plants can use. The heat from fire transforms nitrogen into more easily absorbed organic compounds that fuel photosynthesis, the process by which plants, including trees, capture visible light energy and, with the aid of chlorophyll, convert water from the soil and atmospheric carbon dioxide into glucose (sugar) and oxygen. Glucose is then converted into other organic chemicals, the most common being cellulose—a water insoluble polymer. In trees, these organic compounds are converted to wood fiber.

So yes, there are indeed good forest fires, prescribed as well as wild. But until the underlying causes of the conflagrations that are sweeping the Southwest today are meaningfully addressed such therapeutic disturbances will remain rare. And before the current crisis can be meaningfully addressed—within the framework of a perpetual forest thinning program—the public must create a politically stable climate in which wood fiber consuming businesses can prosper.

  Fire 1

The ecological benefits of thinning and prescribed fire are on display in this series of four photographs taken in Montana’s Lick Creek by Dr. Steve Arno, a fire ecologist who, before his retirement, worked for many years at the Forest Service’s Intermountain Fire Sciences Laboratory in Missoula. The Lick Creek area was heavily logged in the early 1900s, then left to regenerate by itself. The result was a dense stand of trees that needed thinning. The Fire Sciences Laboratory took on the task as part of its ongoing research.

Before thinning. Note the old stump in the foreground partially hidden behind a tree that grew up after the area was logged.

  Fire 2  After thinning. The old stump is plainly visible now because the tree the tree in the foreground has been removed along with many others that crowded the stand. The residual ponderosa stand is now plainly visible. Note the debris on the ground.
  Fire 3  Prescribed fire at night. Fire consumes ground litter, reducing the risk of a later wildfire and preparing the soil for natural reseeding from residual pines. Burning at night, when the air is cool, reduces the risk that the fire will escape.
  Fire 4  The following spring. Mission accomplished: excess woody debris is gone and new vegetation is sprouting. The risk of wildfire has been reduced and residual ponderosas will now begin to grow in earnest. Plant diversity has been increased and the area now provides a much wider variety of wildlife habitat than it did before thinning.

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human need to use natural resources is fundamental to our continued presence on earth."
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