When Active Management of high conservation value forests may erode biodiversity and damage ecosystems by David Lindenmayer, et al., Biological Conservation, 2025
“[T]hinning conducted ostensibly to reduce tree mortality from fire or bark beetles can kill significantly more trees than it prevents from being killed.
“[S]ome of the ecological conditions in forests that have been created by industrial forestry practices are not solvable by more of the same practices that encompass intensive AM [Active Management].”
The role of fuel treatments in mitigating fire risk by Xuezheng Zong, et al., Landscape and Urban Planning, 2024
“[E]ven the most intensive fuel treatment design considered in this study cannot reduce wildfire risk significantly at the landscape scale under the high fire severity condition, which suggested that other fire management measures might have to be integrated.”
The fastest-growing and most destructive fires in the US (2001 to 2020) by Jennifer K. Balch, et al., Science, 2024
“Using satellite data, we analyzed the daily growth rates of more than 60,000 fires from 2001 to 2020 across the contiguous US. Nearly half of the ecoregions experienced destructive fast fires that grew more than 1620 hectares in 1 day. These fires accounted for 78% of structures destroyed and 61% of suppression costs ($18.9 billion).
“The modern era of megafires is often defined based on wildfire size, but it should be defined based on how fast fires grow and their consequent societal impacts. Speed fundamentally dictates the deadly and destructive impact of megafires, rendering the prevailing paradigm that defines them by size inadequate. Although big fires change air quality, ecosystems, and carbon dynamics, fire speed matters more for infrastructure risk and evacuation planning.
“[W]e know that fast fires occur when it is hot, dry, and windy, but relatively little research exists about when and why they occur across regional or national scales. Most of the area burned in extremely large events is from the growth on a single day, which is driven by extreme fire weather.
“We know that the primary mechanism for home ignition is firebrands propelled ahead of the flaming front that land on flammable materials attached to, on, or inside the structure and ultimately consume it. Firefighters can extinguish these building ignitions during slower fires or when structure ignition is mitigated, but during fast-moving events, they are often overwhelmed by the higher number of homes catching fire simultaneously and the need to focus on life safety and evacuations, such as during the 2018 Camp Fire.
“The 10 fastest fires were in grassland-dominated vegetation, which highlights the role of fine, flashy fuels and low wind friction.
“These fast fires represent only 2.7% of all events, yet they account for 89% of the total structures damaged or destroyed.
“Fast fires matter for life safety and structure impacts; large fires matter more for ecosystems and they generate substantial smoke. The speed of a fire determines whether firefighters are more focused on evacuation than home protection and how effectively they can extinguish burning firebrands and new ignitions on structures before the home becomes fully involved.
“It is also known that invasive grasses can drive increases in size, occurrence, and frequency. Because grass-fueled fires are some of the fastest, it may then follow that where vegetation transitions have occurred, for example, from forest or shrubland to invasive grassland, fire speed may have also increased.”
The Impact of Fuel Thinning on the Microclimate in Coastal Rainforest Stands of Southwestern British Columbia, Canada by Rhonda L. Millikin et al., Fire, 2024
“We found that the thinning led to warmer, drier, and windier fire environments.”
“[F]uel thinning also dries out the surface and ground fuels in these forests through the effects of solar radiation and increases in-stand wind penetration, which can in turn increase crown fire potential.”
Setting the Stage for Mixed- and High-Severity Fire by Chad T. Hanson, Dominick A. DellaSala, Rosemary L. Sherriff, Richard L. Hutto, Thomas T. Veblen, William L. Baker, Elsevier, 2024
“Though the unique complex early seral forests created by higher-severity fires are important for a wide variety of biota, they are most often degraded by prefire logging that simplifies the ensuing postfire structure, prescribed burning, fire suppression, land use alterations, and especially postfire logging. Management designed to encourage primarily homogeneous, low-severity fire in areas that historically had mixed-severity fire will not maintain the ecosystem benefits created by these fires.”
“Drier montane forest ecosystems and some shrub habitats are assumed to have been maintained historically by lower-severity fires that created open and park-like structures in western North America. High-severity fires—especially larger patches—are often assumed to be unnatural and ecologically damaging. These assumptions drive current land management policies where fires burn in higher severities. However, evidence indicates that montane forests, including ponderosa pine and mixed-conifer forests, were historically far more variable in tree densities and fire regimes and were maintained by a mixed-severity fire regime.”
“Contemporary Wildfires Not More Severe Than Historically: More Fire of All Severities Needed to Sustain and Adapt Western US Dry Forests as Climate Changes” by William L. Baker, Sustainability, 2024
“[R]educing high-severity fire through fuel reductions is fire suppression, which has significant well-known adverse ecological impacts. These include reductions in (1) natural burn patches, snags, and non-forest openings, that favor diverse fire-adapted species, and (2) landscape heterogeneity that can limit future disturbances and enhance landscape ecological processes.”
“Wildland-urban fire disasters aren’t actually a wildfire problem” by David E. Calkin, Kimiko Barrett, Jack D. Cohen, Mark A. Finney, Stephen J. Pyne, Stephen L. Quarles, Proceedings of the National Academy of Sciences (PNAS), 2023
“[T]he traditional federal and state land-management agencies with responsibilities for wildland fuels management and suppression response have limited impact on community destruction. However, many of the recent investments to address wildfire risk to communities, such as the Bipartisan Infrastructure Investment and Jobs Act of 2021 and the Inflation Reduction Act of 2022, are primarily directed toward fuel treatments in natural areas governed by public land-management agencies.”
“Harnessing Natural Disturbances: A Nature-Based Solution forRestoring and Adapting Dry Forests in the Western USA to Climate Change” by William L. Baker, et al., Fire, 2023
“Mechanical fuel-reduction treatments (e.g., thinning) reduce landscape heterogeneity and appear ineffective since <1% of the treated area encounters fire each year and fires are still increasing…”
“We compared 2010–2019 disturbance rates on ~16 million ha of federal dry forests with historical data. We evaluated how much adaptation is achieved by comparing how trees are selected by treatments and disturbances. We found an NbS [nature-based solution], which works with natural disturbances and prioritizes community protection, is feasible in western USA dry forests since disturbances are occurring mostly within historical rates. Natural disturbances, unlike mechanical treatments, select survivors that are more likely to be genetically adapted to survive future disturbances and climate change, while perpetuating ecosystem services.”
Improved logistic models of crown fire probability in Canadian conifer forests by Daniel D. B. Perrakis, et al., International Journal of Wildland Fire, 2023
“Wind speed has long been known to control ROS [rate of spread] in surface fire and crown fire behaviour models.”
“Wind speed remains the most significant variable in our modelling of crown fire occurrence.”
“Changes in fine fuel moisture dynamics and in-stand micro- climate caused by fuel treatments have often been ignored.”
“Is Climate Change Restoring Historical Fire Regimes across Temperate Landscapes of the San Juan Mountains, Colorado, USA?” by William L. Baker, Land, 2022
“[R]educing fire size or severity is currently ecologically unnecessary. Instead, incorporating fire from climate change, via wildland fire use, supplemented by prescribed burning, could feasibly restore historical fire regimes…”
“Cumulative tree mortality from commercial thinning and a large wildfire in the Sierra Nevada, California” by Bryant C. Baker et al., Land, 2022
“[W]e found significantly higher cumulative severity in forests with commercial thinning than in unthinned forests, indicating that commercial thinning killed significantly more trees than it prevented from being killed…because most previous research has not accounted for tree mortality from thinning itself, prior to the wildfire-related mortality, such research has underreported tree mortality in commercial thinning areas relative to unthinned forest.”
“Cumulative severity of thinned and unthinned forests in a large California wildfire” by Chad T. Hanson, Land, 2022
“[C]ommercial thinning was associated with significantly higher overall tree mortality levels (cumulative severity).”
“Have western USA fire suppression and megafire active management approaches become a contemporary Sisyphus?” by D.A. DellaSala, et al., Biological Conservation, 2022
“[T]he amount of high-severity fire reported in thinning units…was dramatically underestimated…Thus, there is indeed evidence that thinning is not full proof…can be unnecessary, and counter-productive as a landscape fire management tool especially when fires are driven largely by extreme-fire weather that is increasing across the West due to climate change.”
“Extreme Winds Alter Influence of Fuels and Topography on Megafire Burn Severity in Seasonal Temperate Rainforests under Record Fuel Aridity” by C. Evers, et al., Fire, 2022
“Early-seral forests primarily concentrated on private lands, burned more severely than their older and taller counterparts, over the entire megafire event regardless of topography. Meanwhile, mature stands burned severely only under extreme winds and especially on steeper slopes.”
“Adapting western North American forests to climate change and wildfires: 10 common questions” by Susan J. Prichard et al., Ecological Applications, 2021
“Reduced canopy bulk density can lead to increased surface wind speed and fuel heating, which allows for increased rates of fire spread in thinned forests.”
“[M]echanical treatments may increase the risk of fire by increasing sunlight exposure to the forest floor, drying surface fuels, promoting understory growth, and increasing wind speeds that leave residual trees vulnerable to wind throw.”
“[Fuel] treatments generally are designed to mitigate wildfire intensity and effects but they are not necessarily intended to impede fire spread or reduce fire size.”
“Is ‘Fuel Reduction’ Justified as Fire Management in Spotted Owl Habitat?” by Chad T. Hanson, Birds, 2021
“Within the forest types inhabited by California Spotted Owls, high-severity fire occurrence was not higher overall in unmanaged forests and was not associated with the density of pre-fire snags from recent drought…contrary to expectations under the fuel reduction hypothesis. Moreover, fuel-reduction logging in California Spotted Owl habitats was associated with higher fire severity in most cases.”
“Northern spotted owl nesting forests as fire refugia: a 30-year synthesis of large wildfires” by D. Lesmeister, et al., Fire Ecology, 2021
“Some open-canopied forests and younger even-aged and densely stocked stands have hotter, drier, and windier microclimates, and those conditions decrease dramatically over relatively short distances into the interior of older forests with multi-layer canopies and high tree density.”
“How climate change and fire exclusion drive wildfire regimes at actionable scales” by Erin J Hanan, Jianning Ren, Christina L Tague, Crystal A Kolden, John T Abatzoglou, Ryan R Bart, Maureen C Kennedy, Mingliang Liu, Jennifer C Adam, Environmental Research Letters, 2021
“[D]ensity reductions can sometimes have unintended consequences, particularly when vegetation growth is enhanced by treatment, leading to greater ET [evapotranspiration] and ultimately drier conditions.”
“How does tree regeneration respond to mixed-severity fire in the western Oregon Cascades, USA?” by C.J. Dunn, et al., Ecosphere, 2020
“Forests that burned at high-severity had lower, not higher, overall pre-fire tree densities.”
“Influence of topography and fuels on fire refugia probability under varying fire weather in forests of the US Pacific Northwest” by G.W. Meigs, et al., Canadian Journal of Forest Research, 2020.
“Forests with higher pre-fire biomass are more likely to experience low-severity fire.”
Impacts of Forest Thinning on Wildland Fire Behavior by Tirtha Banerjee, Forests, 2020
“[I]t is well understood that thinning of the forest canopy will lead to an increase of wind speed and solar radiation.”
“[A] a thinning level which cleared about half of the basal area of a maturelodgepole pine stand resulted in enhanced in-canopy solar radiation, wind speed and near surface air temperature.”
“The opening of the canopy can entrain more wind and solar radiation which might result in the reduction of fine fuel and canopy fuel moisture. Moreover, if the resultant additional surface fuel accumulation is not removed, it might increase surface loading of fuel. All of these effects could result in enhanced surface fire behavior and increase in crowning potential. There could also be long term consequences such as altered regimes of carbon storage which changes the future fuel loading and altered hydrologic regimes which changes future water stress and fuel moisture.”
“Mixed-severity wildfire and habitat of an old-forest obligate” by Damon B. Lesmeister, Stan G. Sovern, Raymond J. Davis, David M. Bell, Matthew J. Gregory, Jody C. Vogeler, Ecosphere, 2019
“Denser, older forests with high canopy cover had lower fire severity.”
Invasive grasses increase fire occurrence and frequency across US ecoregions, by Emily J. Fusco, et al., PNAS, 2019
“The significant differences in fire regimes, coupled with the importance of grass invasion in modeling these differences, suggest that invasive grasses alter US fire regimes at regional scales. As concern about US wildfires grows, accounting for fire-promoting invasive grasses will be imperative for effectively managing ecosystems.”
Effects of thinning a forest stand on sub-canopy turbulence by Eric S. Russell, et al., Agricultural and Forest Meteorology, 2018
“As the forest was thinned, turbulence and wind speed near the surface (0.13 h) increased and became more connected with above the canopy (1.13 h). The variation of the three-dimensional wind components increased for 0.13 h when the understory was thinned. Turbulence at 0.83 h and 1.13 h increased when whole trees were removed (2nd and 3rd thinning).”
“Severe fire weather and intensive forest management increase fire severity in a multi-ownership landscape” by Harold S. J. Zald, Christopher J. Dunn, Ecological Applications, 2018
“Our findings suggest intensive plantation forestry characterized by young forests and spatially homogenized fuels, rather than pre-fire biomass, were significant drivers of wildfire severity.”
“Modeling thinning effects on fire behavior with STANDFIRE” by Russell A. Parsons, Francois Pimont, Lucas Wells, Greg Cohn, W. Matt Jolly, Francois de Coligny, Eric Rigolot, Jean-Luc Dupuy, William Mell, Rodman R. Linn, Annals of Forest Science, 2018
“STANDFIRE consistently predicted faster surface fires (ROS) and somewhat increased surface fuel heat transfer (QSRF) in thinned stands, due to reduced canopy drag effects…”
“Untreated cases were very resistant to torching, requiring wind speeds in excess of 76 km h−1 for torching for all three sites; thinned cases had lower Torching Index values, indicating increased potential for torching. Conversely, Crowning Index values were low for untreated cases and increased with thinning, indicating decreased potential for crown fire spread.”
“Despite holding surface fuel constant, flame length (FL) increased following thinning in all three sites, likely from decreases in stand level canopy cover and corresponding increases in effective wind speed, ROS, and fireline intensity.”
Restoring and managing low-severity fire in dry-forest landscapes of the western USA by William L. Baker, PLOS One, 2017
“Frequent fire (PMFI/FR < 25 years) was found across only about 14% of historical dry-forest area, with 86% having multidecadal rates of low-severity fire.”
“For most dry-forests today, which are not old, using frequent fire (PMFI/FR < 25 years) in restoration is not supported, and fuels do not need to be substantially reduced, because historical PMFI/FRs naturally allowed historical shrubs and small trees to fully recover after fires.”
“Does increased forest protection correspond to higher fire severity in frequent-fire forests of the western United States?” by Curtis M. Bradley, et al., Ecosphere, 2016
“We found forests with higher levels of protection had lower severity values even though they are generally identified as having the highest overall levels of biomass and fuel loading.”
“[F]orests with the highest levels of protection from logging tend to burn least severely…”
“[U]sing over three decades of fire severity data from relatively frequent-fire pine and mixed-conifer forests throughout the western United States, we found…burn severity tended to be higher in areas with lower levels of protection status (more intense management)…”
“Effects of Fire and Commercial Thinning on Future Habitat of the Northern Spotted Owl” by Dennis C. Odion, et al., The Open Orthopaedics Journal, 2014
“Even if rates of fire increase substantially, the requirement that the long-term benefits of commercial thinning clearly outweigh adverse impacts is not attainable with commercial thinning in spotted owl habitat.”
“Severity of an Uncharacteristically Large Wildfire, the Rim Fire, in Forests with Relatively Restored Frequent Fire Regimes” by Jamie M. Lydersen, Malcolm P. North, Brandon M. Collins, Forest Ecology and Management, 2014
“Our results suggest that wildfire burning under extreme weather conditions, as is often the case with fires that escape initial attack, can produce large areas of high-severity fire even in fuels-reduced forests with restored fire regimes.”
“Using Modeled Surface and Crown Fire Behavior Characteristics to Evaluate Fuel Treatment Effectiveness: A Caution” by Miguel G. Cruz, et al., European Journal of Marketing, 2014
“Although the commercial thinning led to a decrease in the likelihood of active crown fire propagation, it also caused a substantial increase in the surface fireline intensity.”
The efficacy of fuel treatment in mitigating property loss during wildfires by Owen F. Price and Ross A. Bradstock, Journal of Environmental Management, 2012
“Probability of crown fires was higher in recently logged areas than in areas logged decades before, indicating likely ineffectiveness as a fuel treatment.”
“Impacts of tree canopy structure on wind flowsand fire propagation simulated with FIRETEC” by François Pimont, Jean-Luc Dupuy, Rodman R. Linn, Sylvain Dupont, Annals of Forest Science, 2011
“In the case of a clean fuel break (with surface fuel cleared), this increase of wind speed in channels is likely to increase the fire spread.”
Vegetation and weather explain variation in crown damage within a large mixed-severity wildfire by Jonathan R. Thompson and Thomas A. Spies, Forest Ecology and Management, 2009
“Open tree canopies with high levels of shrub-stratum cover were associated with the highest levels of tree crown damage, while closed canopy forests with high levels of large conifer cover were associated with the lowest levels of tree crown damage.”
“Objectives and considerations for wildland fuel treatment in forested ecosystems of the interior western United States” by Elizabeth D. Reinhardt, Robert E. Keane, David E. Calkin, Jack D. Cohen, Forest Ecology and Management, 2008
‘‘[E]xtreme conditions and fire behavior permitted intense surface fire through treated areas…. Fuel breaks and treatments were breached by massive spotting and intense surface fires…Extreme environmental conditions …overwhelmed most fuel treatment effects… This included almost all treatment methods including prescribed burning and thinning…. Suppression efforts had little benefit from fuel modifications.”
“Fire Probability, Fuel Treatment Effectiveness and Ecological Tradeoffs in Western U.S. Public Forests” by Jonathan J. Rhodes and William L. Baker, Open Forest Science Journal, 2008
“[O]ur results indicate that, on average, approximately 2.0 to 4.2% of areas treated to reduce fuels are likely to encounter fires that would otherwise be high or high-moderate severity without treatment. In the remaining 95.8-98.0% of treated areas, potentially adverse treatment effects on watersheds are not counterbalanced by benefits from reduced fire severity.”
“Ground-based methods and associated machine piling, burning of activity fuels, construction and increased use of roads and landings can increase soil erosion, compact soils, and elevate surface runoff…When impacts are extensive, proximate to streams, or in terrain with erosion hazards, treatments can increase runoff and sediment delivery to streams. Road activities that increase sediment production, such as elevated road traffic, often affect stream crossings where sediment delivery is typically efficient and difficult to control. Elevated sediment delivery to streams contributes to water quality degradation that impairs aquatic ecosystems.”
“Patterns of Fire Severity and Forest Conditions in the Western Klamath Mountains, California” by Dennis C. Odion et al., Conservation Biology, 2004
“We concluded that fuel buildup in the absence of fire did not cause increased fire severity as hypothesized. Instead, fuel that is receptive to combustion may decrease in the long absence of fire in the closed forests of our study area, which will favor the fire regime that has maintained these forests.”
“[T]ree plantations experienced twice as much severe fire as multi-aged forests.”
“Influence of clear-cutting on the risk of wind damage at forest edges” by Hongcheng Zeng, et al., Forest Ecology and Management, 2004
“The highest risk of wind damage is most likely to be found where there are sudden changes in wind loading to which the trees are not acclimated, as in stands adjacent to recently clear-felled areas or in stands that have recently been thinned intensively.”
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