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The myth of "catastrophic" wildfire - a new ecological paradigm of forest health

Author(s): Chad T. Hanson
Year Published: 2010

Every fire season in the western United States, we see on television the predictable images of 100-foot flames spreading through tree crowns, while grim-faced news anchors report how many acres of forest were “destroyed” by the latest “catastrophic” fire. The reaction is understandable. For decades, countless Smokey the Bear advertisements have told us that forest fires are bad and damaging. Until about 25 years ago, land management agencies, such as the U.S. Forest Service, genuinely believed that they could essentially eliminate fire from our forests if they had enough resources to suppress fires – and they sought to do just that.

By the late 20th century, however, forestry officials began to concede that, historically, frequent low-intensity fires were natural in our forests, slowly creeping along the forest floor after lightning ignitions, reducing fuel on the forest floor and naturally thinning-out brush and small trees. Though a begrudging acceptance of the benefits of low-intensity fire began to take hold, it was commonly assumed that areas of high-intensity fire, where tall flames killed most of the trees, were fundamentally the unnatural result of fuel accumulations from decades of fire suppression. Thus began the “catastrophic wildfire” paradigm, which divided fires into two categories: good fires and bad fires depending upon whether they burned at low-intensity or high-intensity, respectively.

Recently, however, a new paradigm has begun to emerge, informed by the latest ecological science. Over the past decade, a surge of scientific discovery has led researchers to fundamentally re-think previous assumptions about fire and forest health. In this new “forest ecology” paradigm, scientists have come to understand that high-intensity fires, or “stand-transforming fires”, occurred naturally in most western U.S. conifer forests historically, and we have far less fire now than we did prior to fire suppression policies. Scientists have also come to understand that dead trees, especially large dead trees, or “snags”, are not only the most ecologically valuable habitat features in the forest, but are also far too scarce, due to fire suppression and logging conducted under the guise of fuels reduction and forest health.

Most strikingly, recent scientific evidence has revealed that, contrary to previous assumptions, most current fires are predominantly low-intensity and moderate-intensity, and the relatively scarce high-intensity areas support the highest levels of native plant and wildlife biodiversity of any forest type in the western United States.Scientists now understand that, far from being “destroyed”, these high-intensity patches are actually natural ecological treasures. High-intensity, or stand-transforming, fire creates ecologically-vital “snag forest habitat”, which is rich with large snags, large downed logs, dense pockets of natural conifer regeneration, patches of native shrub habitat, or “montane chaparral”, and large live trees.

Citation: Hanson CT. 2010. The myth of "catastrophic" wildfire - a new ecological paradigm of forest health. John Muir Project Technical Report 1, Winter 2010, (www.johnmuirproject.org), 32 p.
Topic(s): Fire Effects, Ecological - Second Order, Vegetation, Fire History, Frequency, Post-fire Management, Fire Regime, Fire Intensity / Burn Severity
Ecosystem(s): None
Document Type: Technical Report or White Paper
NRFSN number: 16302
Record updated: May 24, 2018