A research paper released yesterday finally did it for us.
“The most profound implication of this study is that the need for forest ‘restoration’ designed to reduce variation in fire behavior may be much less extensive than implied by many current forest management plans or promoted by recent legislation.”
Over the past ten years I have become increasing skeptical of the notion that large, high-severity fires in Western forests are “unnatural” and are completely the result of fuel build-up due to past fire suppression. A comment made last summer by a fire scientist during the Rim Fire in Yosemite that historically in the western Sierra the maximum high-intensity fire patch size was 40 acres with a few acres being the norm was, for me, completely illogical. The press loved it though.
Having read hundreds of research papers, hiked in the Sierra Nevada all my life, having some experience with fire as a USFS seasonal firefighter, watched huge fires move in drought-stressed, low humidity, windy conditions, and observed billions of dollars being spent to “restore” forests by clearing out habitat (i.e. “fuel”), I’ve concluded the conventional wisdom that “forests-are-supposed-to-be-park-like-with-only-surface-fires-clearing-out-the-understory-every-5-10 years,” really needs to go.
Yesterday, a remarkable paper was released that examined “the historical and current mixed-severity fire regimes in ponderosa pine and mixed-conifer forests of western North America.” The scientists examined a huge landscape-data set (from published literature and information on stand ages from the Forest Inventory and Analysis program) about forests across the entire West.
Their conclusion? The traditional reference conditions of low-severity fire regimes are inaccurate for most forests in western North America. Most forests appear to have been characterized by mixed-severity fire that included ecologically significant amounts of weather-driven, high severity fire.
Some of the findings of the paper particularly struck us.
– The way we talk about fire (the nomenclature we use to describe fire regimes) is inherently biased. We classify fire regimes in dry western forests into two basic categories: 1) low, mixed, and high severity or 2) low/moderate-severity and high severity. Nearly ALL fire regimes include a mix of all three severities, including high severity. We need to communicate that more accurate “mixed-severity” picture.
– Where fire has been successfully excluded in forests, high-severity patches indicative of a mixed-severity regime are particularly difficult to detect. Typical methods used to determine fire history, like tree rings, cannot effectively determine past occurrence of high-severity fire.
– There is a critical need for studies with a spatial scale of interference (fire) suited to describing patterns across large, heterogeneous landscapes.
– USGS surveys from the 1890s including Leiberg’s in 1902 all point to substantial high-severity fire in the past. Such descriptions are usually omitted in documents promoting the “park-like” forest paradigm.
– Large areas of forests burned in high-severity fire are still forests. They provide critical habitat for wide array of species, many of which are either threatened or endangered.
How does chaparral fit into this? Chaparral and shrubs have been branded as the evil understory in need of immediate mitigation. The following quote taken from the paper should help set the record straight.
In describing low/mid-elevation forests throughout the northern Sierra Nevada, Leiberg [1902, 51: page 32) states: ‘‘There is a great amount of undergrowth in the forest which has attained its present proportions chiefly through the agency of fire. Most of it [undergrowth] consists of species of Ceanothus.”For mid-elevation forests, he reports (page 37): ‘‘Nearly all the type situated ataltitudes below 7,000’ [2134 m] carries a vast amount of undergrowth. It consists mainly of manzanita [Arctostaphylos spp.], ceanothus, and scrub oak [Quercus chrysolepis, Q.vaccinifolia].’’ Similarly abundant shrub fuels were also documented historically in the westside of the central/southern Sierra Nevada , in the eastern Oregon Cascades [56: Appendix A] and in Oregon’s Blue Mountains . Flame lengths in actively burning manzanita and ceanothus are typically 4–5 times the ,1–2 m height of the shrubs, sufficient to cause ignition of forest canopy tree crowns under favorable burning conditions. Many of these shrub species recruit primarily, if not exclusively, after severe fire, and their occurrence is a further indication of the historical presence of such fire .
You can download the paper here:
Odion, D.C., C.T. Hanson, A. Arsenault, W.L. Baker, D.A. DellaSala, R.L. Hutto, W. Klenner, M.A. Moritz, R.L. Sherriff, T.T. Veblen, and M.A. Williams. 2014. Examining Historical and Current Mixed-Severity Fire Regimes in Ponderosa Pine and Mixed-Conifer Forests of Western North America. PLoS ONE 9(2): e87852. doi:10.1371/journal.pone.0087852
For additional research on the subject of forests and why the current fire paradigm needs to be rejected, six comment letters written to the USFS on their Rim Fire “Salvage” Project are excellent. The research cited within is overwhelming. We have linked them below.
From Sierra Forest Legacy
From biologist Monica Bond
From hydrologist Jonathan J. Rhodes
From the Center for Biological Diversity and The John Muir Project
From the California Native Plant Society
From us, the California Chaparral Institute
Yellowstone National Park