Portions of a forest burned by a 2,700-acre fire in California’s Lake Tahoe Basin were left intact (top), retaining severely burned forest habitat for pyrophilic organisms. In logged areas, however, far fewer burned trees remain. In the 1,800-acre cougar Butte fire in california’s Modoc National forest (bottom), trees marked with an orange “W” (visible on tree at left) were spared, but such isolated trees cannot satisfy the needs of fire- and snag-dependent wildlife. Credit: Stephen A. Shunk
During the 2012 fire season from June through August, wildfires in the drought- stricken western and central United States burned more than 3.6 million acres of forest and shrubland. In the hot, dry, windy conditions seen that season, a single spark can start an understory fire that ascends into the canopies of overstory trees and results in a ‘mega-fire’ that escapes control efforts, threatens human life and property, and chars wide swaths of forest. But in the after- math, a host of pyrophilic organisms such as fire morel mushrooms (Morchella elata), Bicknell’s geraniums (Geranium bicknellii), jewel beetles (Melanophila acuminate), and black-backed woodpeckers (Picoides arcticus) exploit these burned areas for critical habitat elements that are abundant only after such large-scale disturbances. These species are not merely opportunistic. Their distribution is often restricted to severely burned forest conditions.
Forest fires, particularly those that burn at mixed and high severity (collectively called ‘severe’), have been traditionally perceived as catastrophic events, directing public attention and immense forest management budgets toward fire prevention and suppression. These fires may indeed be catastrophic when measured by losses of human lives and property. However, severe fires in wildland areas are both natural and necessary to maintain the integrity of dynamic, disturbance-adapted forest systems. We propose a change in the current paradigm—which holds that severe forest fires are always harmful—to a new one that embraces their ecological necessity.
Fire regimes—the pattern, frequency, and intensity of wildfires—are highly variable among forest types and regions, and fire severity differs with vegetation type, geographical location, management history, and weather. Severe fire is natural in forests in all regions of the U.S., and only mixed- and high-severity fires are intense enough to initiate ecological succession across all regimes. High-severity fires, also called stand-replacement or crown fires, cause widespread mortality of existing vegetation and result in a forest structure no longer dominated by live trees but by herbs, shrubs, and dead trees or snags (Smith 2000, Saab and Powell 2005). In contrast, low-severity or understory fires consume ground-layer vegetation and duff, but rarely kill overstory trees and do not substantially alter forest structure (Smith 2000, Schoennagel et al. 2004). Mixed-severity fires cause patchwork mortality due to species’ varying fire tolerance or because of a combination of high- and low-severity burn patches. Both mixed- and high-severity fires can create burn patches of different size and severity, resulting in a complex mixture of habitats (Baker 2009).
Forest fire management practices strive to alter natural fire regimes by reducing the frequency, intensity, or extent of fires. On public and private lands, fire-fighting crews target man-made fires of any severity, whereas fires caused by natural igni- tions may be permitted to burn under supervision on some public lands. When a fire begins, crews are deployed by the responsible agency to cut firebreaks or set up intentional burns that move in the direction of the fire’s front line, depriving it of the fuel it needs to advance. Under extreme weather conditions such as strong winds and high temperatures, fires are difficult to control, so firefighters often focus instead on protecting structures and evacuating vulnerable areas. Pre-fire treatments such as logging and prescribed burning to reduce fuel load are widespread in managed forests.
Post-fire Winners and Losers
At first glance, a stand of scorched, dead trees in a severely burned forest may appear to be an eco- logical wasteland. Yet many species of plants and animals actually increase in abundance following high-severity fire, and some species depend on severe fire to meet their ecological requirements. Severe fire is a natural element of healthy, dynamic forest ecosystems and even riparian forests in Canada and the western U.S., as it has been for eons (Arkle and Pilliod 2010). Indeed, fire is as essential as rainfall and sunlight to many forest species.
As with any natural disturbance, severe fire leaves winners and losers. Species that depend on unburned, green forests will suffer habitat loss in severely burned stands. Golden-crowned kinglets (Regulus satrapa) and Townsend’s warblers (Setophaga townsendi), for example, forage in the canopies of living trees in western coniferous forests, and will lose ground.
But many other species benefit. Some of the earliest to arrive after severe fire are bark beetles (Coleoptera: Curculionidae, subfamily Scolytinae) and wood-boring beetles (Coleoptera: Buprestidae, Cerambycidae). These specially adapted beetles are equipped with sensory organs that detect smoke and heat from kilometers away, prompting them to swarm in huge numbers to newly charred forests where they deposit millions of eggs onto the bark of dead and dying trees (Evans 1964, 1966; Hart 1998; Saint Germain et al. 2004). The eggs soon hatch into larvae that either burrow between the bark and cambium or into the sapwood. Woodpeckers that thrive on beetle larvae arrive next, particularly in areas with a high density of dead trees, their numbers peaking within the first few post-burn years (Saab et al. 2007, Hutto 2008, Hanson and North 2008).
Many specialized shrub and flower seeds require fire for germination, as do those of serotinous pines, and thrive in soils that are enriched by burned vegetation. Blooming annuals and perennial shrubs attract legions of insects which become prey for insectivores. Some insectivorous birds, such as mountain bluebird (Sialia currucoides), house wren (Troglodytes aedon), olive-sided flycatcher (Contopus cooperi), and even the flycatching Lewis’s woodpecker (Melanerpes lewis), are so well adapted to feed upon the post-fire insect bonanza that they occur at their highest densities in forests that recently burned at mixed and high severity.
For example, in a study of pre- and post-fire bird abundance in coniferous forests of Montana’s Bitterroot National Forest, olive-sided flycatchers increased by an average of four birds at moderately burned point count stations and more than 21 at high-severity burned stations. Likewise, mountain bluebirds increased by more than five and 18 birds, respectively (Smucker et al. 2005). In New Mexico mixed-conifer forests, house wren density nearly quadrupled at high-severity burned sites over unburned sites (Kotliar et al. 2007). Similar results were documented in a diversity of mountainous coniferous forests in Montana, Wyoming (Hutto 1995), Idaho (Saab et al. 2007), Arizona, New Mexico (Bock and Block 2005), southwestern Oregon (Fontaine et al. 2009), and California’s Sierra Nevada (Raphael et al. 1987).
Bats also benefit from the fire-induced pulse of insect prey. In central Idaho’s mixed-conifer forests, emerging adult aquatic insects increased fivefold while bat detections increased fourfold in severely burned versus unburned or lightly burned water- sheds (Malison and Baxter 2010). Bats also roost in burned out basal tree hol- lows, and they benefit from increased sunlight penetration through fire-created tree canopy gaps, which aids their thermoregulation (Boyles and Aubrey 2006, Johnson et al. 2009, Lacki et al. 2009). As early as the 1950s, studies of mule deer (Odocoileus hemionus) documented increased population size and reproductive rates in a variety of ecosystems, including shrub lands, open woodlands, and conifer forests. For example, in severely burned California chaparral, deer population densities were two (Ashcraft 1979) to four (Biswell 1961) times greater, and there were nearly twice as many fawns per doe (Taber and Dasmann 1957, Biswell 1974). In addition, deer droppings were significantly more abundant in burned than unburned pinyon-juniper woodlands in Arizona, with 35 pellet groups per acre per month versus 26, respectively (McCullough 1969). The availability (Snyder 1991) and palatability (Zimmerman et al. 2006) of vegetation eaten by deer increased after fire, and deer preferred to forage in burned forests as long as dead trees were left standing to provide protective cover in pinyon- juniper forests in Arizona (McCullough 1969) and lodgepole pine (Pinus contorta) forests in Wyoming (Davis 1977).
The ability to use severely burned forests even extends to some unlikely characters, including the spotted owl (Strix occidentalis), the classic poster-child for dense, old-growth forests. Spotted owls tend to nest and roost in forests with dense cano- pies and larger trees, but they may benefit from fires that create more open habitat patches ideal for hunting prey (Bond et al. 2009). Spotted owls have relatively large territories, and they will occupy areas containing high-severity burns, as long as some unburned or lightly burned habitat remains for nesting and roosting (Bond et al. 2002, Jenness et al. 2004, Roberts et al. 2011, Lee et al. 2012).
As it excavates a nest cavity in California’s Lassen National Forest, a black-backed woodpecker (Picoides arcticus) emerges from a charred tree to dump a beakful of wood. Many species of birds, mammals, insects, and plants depend on high-severity forest fires to complete their lifecycles. Credit: Joseph Leibrecht
An Icon for Burned Forests
Controversy over fire management in forests that experience mixed- and high-severity fire regimes has grown, and one pyrophile speaks loudest for species that benefit from severe fire—the black- backed woodpecker. This bird is perhaps the most iconic winner in the post-fire landscapes of the western U.S. and Canada. Abundant research from California to Quebec consistently confirms the bird’s strong affinity for severely burned forests throughout its range, positioning it as one of the most specialized North American birds—one with a distribution that matches the historical footprint of severe fire (Hutto et al. 2008).
The black-backed woodpecker makes use of both large and small patches of dead trees for nesting and foraging, reaching its highest densities in forests with numerous trees recently killed by fire (Hutto 1995, 2008, Saab et al. 2007, Vierling et al. 2008, Saab et al. 2009, Saracco et al. 2011). In a survey of 16,465 point count stations spanning 14 years and 20 vegetation types throughout northern Idaho and Montana, Hutto (2008) documented that 96 percent of all black-backed woodpeckers occurred in burned forest stands. The species may be the best-adapted woodpecker in the world for extracting wood-boring beetle larvae from fire-killed trees. The black-backed and many other woodpecker species play a keystone ecological role in burned forests by excavating nest cavities that are later used by secondary cavity-nesting birds (Saab et al. 2004), including western and mountain bluebirds, house wrens, and small forest owls. Woodpecker cavities are also utilized by innumerable forest invertebrates and mammals, such as martens (Martes americana), fishers (Martes pennanti), and several bat and squirrel species.
A group of conservation organizations recently petitioned the U.S. Fish and Wildlife Service to give the California, Oregon, and South Dakota populations of the black-backed woodpecker protection under the Endangered Species Act. If listed, the bird would become the first protected animal species that is associated with severely burned forests.
Changing the Fire Paradigm
Land management agencies have long embraced the ecological role of low-severity fire in forest ecosys- tems, that is to maintain sparse, open stands of larger trees by burning grasses and litter and killing smaller trees (Noss et al. 2006). Yet high-severity fire continues to be viewed negatively by some land
managers and the general public. These attitudes are reinforced by the Smokey Bear ad campaign of the U.S. Forest Service and the National Association of State Foresters. Videos and posters teach the public that the only good fires are prescribed, low-severity fires that recreate the beneficial effects of natural ones while avoiding catastrophic losses associated with uncontrolled fires. This message, along with management directives promulgating suppression of high-severity fires, persists despite evidence that the creation of abundant snag-dominated stands that occur in the wake of severe fire are critical to many species in Canada and the western U.S. (Saab and Powell 2005, Kotliar et al. 2007, Hutto 2008, Fontaine and Kennedy 2012).
A growing body of research suggests that the current fire paradigm—that low-severity fire is natural and high-severity fire is unnatural and undesirable—may be changing. Two-thirds of all wildlife species use snags or other woody debris which is abundant in a post-fire landscape for some portion of their life cycles (Brown 2002). Numerous studies on the widespread practice of post high-severity fire salvage logging have documented adverse effects on the black-backed woodpecker and other cavity- nesting bird species (e.g., Hutto and Gallo 2006, Hutto 2006, Hanson and North 2008, Cahall and Hayes 2009, Saab et al. 2007, 2009, 2011). Post-fire logging reduces the density and diversity of snag sizes, which in turn reduces nesting habitat. For example, nesting densities of black-backed wood- peckers in western Idaho were five times lower in partially salvage-logged stands than in unlogged stands (Saab et al. 2007). And in the Sierra Nevada, black-backed woodpeckers preferentially foraged in severely burned stands with larger snags and higher snag densities (Hanson and North 2008). These studies raise concerns over the impacts of logging in recently burned forests in Canada and the western U.S. and emphasize the unique ecological role of high-severity fire in these habitats.
Some forest managers have begun to recommend retaining some stands of severely burned forests in their management plans. For example, the Sierra Nevada Forest Plan Amendment in California proposes guidelines for retaining at least 10 percent of severely burned forest stands during post-fire logging operations, and actual retention rates have often been higher than that. These are promising recommendations, but unfortunately because they are not based on a thorough analysis of the habitats required to sustain fire-dependent species, it is not clear whether 10 percent retention is high enough to ensure that the protected areas contain the density and variety of snags needed to provide adequate foraging substrate and nesting and shelter opportunities for wildlife in the post-fire ecosystem.
The U.S. Forest Service Pacific Northwest Region (PNR) took a step in this direction by developing a tool that uses scientific data on wildlife habitat relationships with dead wood to help managers make decisions on sizes and amounts of snags to retain for wildlife needs in Washington and Oregon forests (Mellen-McLean et al. 2012). The tool—called DecAID—presents solutions to meet wildlife management objectives in specific, quantitative terms that can be monitored. DecAID has been used in every NEPA document developed by National Forests in the USFS Pacific Northwest Region since 2006, resulting in more scientifically rigorous environmental analyses and reduced litigation (Kim Mellen-McLean, PNR Ecologist, personal communication, October 2012).
Now is the time to recognize the critical ecological value of severely burned forests so that the public and the agencies under its trust can begin to accept and even welcome mixed- and high-severity fires. This can be accomplished by collating the extensive body of scientific literature on the importance of post-fire habitats and the harm caused by snag removal in these systems, and by making this information easily available to decision-makers and the media. Scientists and forest biologists working in fire-adapted forest ecosystems need to become effective spokespeople for the new paradigm.
Only with regulatory protection for burned habitats can fire-dependent organisms thrive. Where con- servation of wildlife and maintenance of ecological processes is the management goal, such protections include allowing naturally ignited and man-made fires of all severities to occur in wildland areas, and curtailing post-fire salvage-logging, with a focus on retaining large patches with high snag densities. Continued research into natural post-fire succession and habitat needs of wildlife in unlogged post-fire ecosystems will provide valuable insights into how to best manage disturbance-adapted forests to pro- tect and enhance biological diversity.
Author Bio: Monica L. Bond, CWB, is a Principal Scientist for the Wild Nature Institute in Hanover, New Hampshire.
Co-author Bios: Rodney B. Siegel, Ph.D., is the Executive Director of the Institute for Bird Populations at Point Reyes Station, California.
Richard L. Hutto, Ph.D., is the Director of the Avian Science Center and a Professor of Biology at the University of Montana in Missoula.
Victoria A. Saab, Ph.D., is the Director of the Birds in Burns Network and a Research Wildlife Biologist at the USFS Rocky Mountain Research Station in Bozeman, Montana.
Stephen A. Shunk is a Professional Naturalist, Field Biologist, and Author based in Bend, Oregon.
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Bond et al.: Thanks for the thought-provoking article. I’d like to make several points to the contrary using a very West or Sierra Nevada centric perspective. First, those pyrophiles are in luck; annual area burned at high severity is indeed increasing in much of the west (Miller and Stafford 2012, Dillon et al. 2011, Lutz et al. 2009, etc.). In your introductory paragraph you mention that “…exploit these burned areas for critical habitat only after such large-scale disturbances”. Are you sure they have to be large scale? Many of the forest types in the Sierra Nevada were historically “mixed severity” fire regimes which implies some high severity patches but also low and moderate (severity). I think lower and upper bounds on high severity patch size further nuances your list of winners and losers. If patches are too large, trees may not regenerate so these patches do not regenerate black backed woodpecker habitat. If patches are too small they do not create canopy gaps large enough for pine regeneration. Also, large patches of high severity fire do not have historical precedence everywhere – all the fire history studies using fire scars in trees suggest that low and moderate severity fire dominated those forest types. Trees stop collecting data for us after high severity fire. You also mention that low severity fire does not alter forest structure. Recently we (Kane et al. 2013) demonstrate using LiDAR that low severity fire (as measured by RdNBR) does change the structure of the forest and not just the “ground layer vegetation and duff”. Lastly, Lutz et al. (2012) demonstrated that large diameter trees comprise 1.4% of the trees in old forests (Yosemite National Park) but contain 49.4% of the biomass. From a greenhouse gas perspective, the carbon is in the big trees and keeping those trees alive will be part of a sequestration solution. It seems to me that your article could be improved with greater attention to scale of disturbance. Fire regimes in the Sierra Nevada suggest “complex” patterns of fire severity such that antecedent fires influence severity and spatial pattern and extent of subsequent fires. Thanks.
Gus, we did not mean to imply that severely burned patches need to be large. Severe patch sizes vary right along with variation in fire regimes, as Baker (2009) discusses in his book. This huge intellectual breakthrough arrived a bit earlier with the Sugihara et al. (2006) chapter on fire as an ecological process, where they made it clear that ALL aspects of a fire regime (including the sizes of different severity patches) have distributions. That means even low-severity fire regimes can be characterized by a certain amount of high-severity fire. It also means that the “one size fits all” management encouraged by the use of averages rather than distributions needs to change.
Baker, W. L. 2009. Fire ecology in Rocky Mountain landscapes. Island Press, Washington, D.C.
Sugihara, N. G., J. W. van Wangtendonk, and J. Fites-Kaufman. 2006. Fire as an ecological process, p. 58-74. In N. G. Sugihara, J. W. van Wangtendonk, J. Fites-Kaufman, K. E. Shaffer, and A. E. Thode [eds.], Fire in California’s ecosystems. University of California Press, Berkeley, CA.
Thank you Mr. Stubblefield for your comments on our paper “A New Forest Fire Paradigm.” I am one of the co-authors, along with several esteemed wildlife biologists who have conducted research in fire-affected forests. The point raised about severe fire adversely affecting watersheds and water quality is interesting but also in need of a new paradigm. According to recent research using sediment cores from lakes, severe fire over the past 2,000 years resulted in sedimentation similar to that after severe fires today, but that sediment loads from logging and road building was more than fourfold greater than that with the most severe presettlement fires (Colomaroli and Gavin 2010). In other words, today’s fires have a presettlement precedent. Swanson et al. (2011) noted that erosion and landslides may occur at higher rates after severe fire but this creates long-lasting substrates for ruderals and provides materials and processes that counteract the effect such as woody debris. Research on the Biscuit and B&B fires in Oregon found rapid vegetation regeneration in riparian areas following severe fires, indicating high resilience in these disturbance-adapted forests (Halofsky and Hibbls 2009). These papers also note that post-fire salvage-logging hampers these natural post-fire processes. I strongly encourage Mr. Stubblefield to take a look at the scientific literature on this topic that provides support for the new forest fire paradigm. Many thanks, Monica Bond
Mary, I think I must have messed up on that statistic, which I reported in an earlier publication…not sure why. All I see in Brown is a note that some 90 vertebrates depend on snags. Maser et al. (pp.78-95 in J. W. Thomas [ed.] 1979. Wildlife habitats in managed forests: the Blue Mountains of Oregon and Washington. U.S. Department of Agriculture, Forest Service, Agriculture Handbook No. 553, Washington, D.C.) note that 179 of 378 vertebrate species (47%) make use of snags. Suffice it to say that a multitude of species depend on dead wood.
Can somebody steer me to the text in Brown 2002 that is the source for the authors’ claim, “Two-thirds of all wildlife species use snags or other woody debris which is abundant in a post-fire landscape for some portion of their life cycles (Brown 2002)”? I read through the reference and searched for a variety of words,to no avail. I love the statistic, but is the citation correct? Thanks.
Ms. Bond’s conclusions that catastrophic (or severe) wildfires on public landscapes “has a great many benefits” and perhaps should be looked at more favorably as a new paradym is interesting, but she and others supporting such a conclusion, have seemingly overlooked one giant consequence of greater importance —– that being the destruction of not only watersheds in the wake of such fires, but the #1 product off these forests, WATER quality. The day is coming when the general public will finally realize that their water does not come from “the city water tanks” but from the uplands many of which originate on national forests. To “desire” such outcomes is pure hypocritical nonsense and demonstrates a complete lack of experience with fire behavior and effects. Go back to the drawing board with this hypothesis at the Wild Nature Institute!
Ted, you state that we overlooked the “destruction” of watershed and water quality by severe fire events. Yes, but we have to start somewhere. It’s hard enough for terrestrial ecologists to convince the public that there is any conceivable ecological benefit following a timber-destroying, catastrophic wildfire, but our challenge pales in comparison with the challenge that aquatic ecologists face!
Indeed, watersheds also need runoff from severe fire events to restore conditions therein. The persistent view that severe natural disturbance events are destructive is exactly what we’re trying to combat. Fisheries have never been better for endangered bull trout in the North Fork of the Blackfoot, for example, than after the debris flows from severe 1988 fires “restored” coarse woody debris and potential redds in the watershed. It is runoff from roads that contributes most to unnatural amounts of sediments in streams…severe fire is not the problem.
The following references dealing with watershed “health” might help change your perspective:
Benda, L., D. Miller, P. Bigelow, and K. Andras. 2003. Effects of post-wildfire erosion on channel environments, Boise River, Idaho. Forest Ecology and Management 178:105-119.
Rieman, B., D. Lee, D. Burns, R. Gresswell, M. Young, R. Stowell, J. Rinne, and P. Howell. 2003. Status of native fishes in the western United States and issues for fire and fuels management. Forest Ecology and Management 178:197-211.
Rieman, B. E., R. E. Gresswell, M. K. Young, and C. H. Luce. 2003. Introduction to the effects of wildland fire on aquatic ecosystems in the Western USA. Forest Ecology and Management 178:1-3.
Vieira, N. K. M., W. H. Clements, L. S. Guevara, and B. F. Jacobs. 2004. Resistance and resilience of stream insect communities to repeated hydrologic disturbances after a wildfire. Freshwater Biology 49:1243-1259.
Burton, T. A. 2005. Fish and stream habitat risks from uncharacteristic wildfire: Observations from 17 years of fire-related disturbances on the Boise National Forest, Idaho. Forest Ecology and Management 211:140-149.
Olson, D. L., and J. K. Agee. 2005. Historical fires in Douglas-fir dominated riparian forests of the southern Cascades, Oregon. Fire Ecology 1:50-74.
Dunham, J. B., A. E. Rosenberger, C. H. Luce, and B. E. Rieman. 2007. Influences of wildfire and channel reorganization on spatial and temporal variation in stream temperature and the distribution of fish and amphibians. Ecosystems 10:335-346.
Malison, R. L., and C. V. Baxter. 2010. The fire pulse: wildfire stimulates flux of aquatic prey to terrestrial habitats driving increases in riparian consumers. Canadian Journal of Fisheries and Aquatic Sciences 67:570-579.
Rieman, B. E., P. F. Hessburg, C. Luce, and M. R. Dare. 2010. Wildfire and management of forests and native fishes: conflict or opportunity for convergent solutions? BioScience 60:460-468.
Just wanted to thank you for your informative article. Post-fire salvage operations are indeed a complex issue. The large FS OHV trail system on the Mendocino NF was impacted by this summer’s Mill Fire and addressing post-fire salvage operation impacts to those structures is the focus of a lot of public comment letters.
Best regards,
Don Amador, President
Quiet Warrior Racing/Consulting