Article

# Fire Probability, Fuel Treatment Effectiveness and Ecological Tradeoffs in Western U.S. Public Forests

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## Abstract

Fuel treatment effectiveness and non-treatment risks can be estimated from the probability of fire occurrence. Using extensive fire records for western US Forest Service lands, we estimate fuel treatments have a mean probability of 2.0-7.9% of encountering moderate-or high-severity fire during an assumed 20-year period of reduced fuels.

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... At the stand level, fuel treatment effects vary according to treatment type, size, and age [10], while their spatial arrangement and rate of implementation can affect outcomes at the landscape level [11,12]. One principal critique of fuel treatments is that their benefits are rarely realized because of the low likelihood that an unplanned fire will encounter a previously treated area during its effective lifespan [13][14][15], though the rate and extent to which this occurs remains largely unknown. ...
... Due to data limitations, previous attempts to characterize fire and fuel treatment interactions in the United States made broad assumptions when estimating the probability that treated areas would burn by unplanned fire [14], most notably the assumption that fire and fuel treatments are randomly located. Findings based on such assumptions may have limited ability to inform contemporary fire and fuels management strategies because the likelihood of fire occurrence and spread is known to exhibit spatial patterning and be highly variable across large landscapes [27,28]. ...
... Prior efforts have quantified interactions between certain types of fuel treatments and subsequent fire. Rhodes and Baker [14] estimated that between 7.2% and 16.5% of treated areas in ponderosa pine forests of the western United States are encountered by fire within 20 years of treatment assuming random locations of fire and fuel treatments. An empirical study in southeastern Australia found that 22.5% of all prescribed fire patches were subsequently burned by unplanned fire within five years [43]. ...
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In the United States, fuel reduction treatments are a standard land management tool to restore the structure and composition of forests that have been degraded by past management. Although treatments can have multiple purposes, their principal objective is to create landscape conditions where wildland fire can be safely managed to help achieve long-term land management goals. One critique is that fuel treatment benefits are unlikely to transpire due to the low probability that treated areas will be burned by a subsequent fire within a treatment's lifespan, but little quantitative information exists to corroborate this argument. We summarized the frequency, extent, and geographic variation of fire and fuel treatment interactions on federal lands within the conterminous United States (CONUS). We also assessed how the encounters between fuel treatments and fires varied with treatment size, treatment age, and number of times treated. Overall, 6.8% of treatment units evaluated were encountered by a subsequent fire during the study period, though this rate varied among ecoregions across the CONUS. Larger treatment units were more likely to be encountered by a fire, and treatment units were most frequently burned within one year of the most recent treatment, the latter of which is likely because of ongoing maintenance of existing treatments. Our results highlight the need to identify and prioritize additional opportunities to reduce fuel loading and fire risk on the millions of hectares of federal lands in the CONUS that are in need of restoration.
... For instance, the estimates of potential water yield effects in Podolak et al. (2015) are primarily based on forest removal under the rubric of such aims. Ostensibly, these fire-related treatments would tend to be concentrated in drier rather than wetter forests because the former burn more frequently, potentially have more altered fire regimes, and have a greater likelihood of treatments affecting fire behavior (Schoennagel et al., 2004;Rhodes and Baker, 2008). For these combined reasons, Marvin's (1996) estimate of 13 mm in mean annual water yield per 10% reduction in forest cover in the range of mean annual precipitation levels estimated to occur throughout the Sierra Nevada is likely a better estimator than that derived for areas with relatively high levels of mean annual precipitation. ...
... This approach would also require periodic additional watershed entries for re-treatment to kill vegetation in areas where it has been previously removed (Bales et al., 2011;Podolak et al., 2015) or additional removal of forests. Due to regrowth of vegetation, periodic re-treatment or additional forest removal is also required to maintain fuel reductions from initial forest removal (Finney et al., 2007;Rhodes and Baker, 2008). Forest removal that opens forest canopies, such as significant thinning, creates a selfperpetuating need for repeated treatment because they stimulate vegetation regrowth (Noss et al., 2006;Baker, 2009). ...
... Based on the foregoing, the following assessments of associated environmental costs are based on the estimate that at least 25% of watershed area will undergo forest removal involving mechanical forest removal or prescribed burning that would occur at a frequency of ca. 10 years in order to initiate or maintain increases in water yields. This is within the range of the estimated 7-20 year frequency of vegetation removal necessary to maintain reduced fuel levels in treatments aimed at modifying fire behavior (Finney et al., 2007;Rhodes and Baker, 2008;Robichaud et al., 2010). ...
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... While there is general agreement that removing and reducing fuels reduces fire intensity, not all agree that fuel treatments are effective, and many assessments of treatment effectiveness are qualitative or based on simulation models with little empirical data. Rhodes and Baker (2008) found that fuel treatments only have a mean probability of 2.0 to 7.9 percent of being encountered by moderate or high severity fire within 20 years following treatment, and they argue that the millions of dollars spent on fuel treatments is, therefore, not justified. Rhodes and Baker (2008) argue that, even if those areas benefited from reduced burn severity, they are too small to counterbalance the adverse effects of fuel treatments on watersheds. ...
... Rhodes and Baker (2008) found that fuel treatments only have a mean probability of 2.0 to 7.9 percent of being encountered by moderate or high severity fire within 20 years following treatment, and they argue that the millions of dollars spent on fuel treatments is, therefore, not justified. Rhodes and Baker (2008) argue that, even if those areas benefited from reduced burn severity, they are too small to counterbalance the adverse effects of fuel treatments on watersheds. ...
... However, Rhodes and Baker (2008) oversimplified their analysis by assuming that ignitions, and fuel treatments, are randomly distributed across the 11 western states. Neither assumption is correct, as 50 percent of fuel treatments are mandated to occur in the WUI (but see Schoennagel and others 2009 and discussion below). ...
Article
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This report provides managers with the current state of knowledge regarding the effectiveness of fuel treatments for mitigating severe wildfire effects. A literature review examines the effectiveness of fuel treatments that had been previously applied and were subsequently burned through by wildfire in forests and rangelands. A case study focuses on WUI fuel treatments that were burned in the 2007 East Zone and Cascade megafires in central Idaho. Both the literature review and case study results support a manager consensus that forest thinning followed by some form of slash removal is most effective for reducing subsequent wildfire severity.
... A more comprehensive study from Southeastern Australia found that unplanned fires usually burn through prescribed patches, as soon as 1 year after their implementation (Price and Bradstock 2010). Elsewhere, it has been noted that large unplanned fires are rarely affected by prescribed fire patches because either they rarely encounter patches (Rhodes and Baker 2008) or simply burn around them (Dunn 1989) and that no effect of prescribed fire on unplanned fire area can be detected (Keeley 2002). However, there is some evidence that prescribed burn patches cause shadows of unburned vegetation on their lee side (Finney et al. 2005). ...
... 4. Leverage is positively related to the extent of fire. This hypothesis was prompted by the findings of Rhodes and Baker (2008) and Price and Bradstock (2011), who both found that most prescribed fire patches in forest were not encountered by a subsequent unplanned fire within 5 years. ...
... This was the finding in Price and Bradstock's (2010) empirical study of prescribed fire patches in the Sydney region: only 20% of the 670 patches examined were encountered by an unplanned fire within 5 years. The same phenomenon has been observed in forests in the United States (Rhodes and Baker 2008). Note that in the study of Loehle (2004), the single unplanned fire occupied approx-imately 50% of the untreated landscape. ...
Article
Prescribed burning for fuel reduction is a major strategy for reducing the risk from unplanned fire. Although there are theoretical studies suggesting that prescribed fire has a strong negative influence on the subsequent area of unplanned fire (so-called leverage), many empirical studies find a more modest influence. Here, I develop a series of simulations to explore the landscape drivers of leverage. Leverage declines with treatment level in a nonlinear, "decay" relationship, implying diminishing effectiveness. The spatial configuration of the prescribed fire treatment has a major effect: long linear (gridded) barriers are far more effective than patch barriers, but gaps in the grid lead to large reductions in leverage. However, the extent of unplanned fires in the landscape has the largest influence such that a landscape with 3% annual extent has only one-fifth of the leverage of a landscape with 28%. Leverage decreases with the probability of spread, suggesting that treatment is less effective when fire weather is severe. For gridded designs, leverage increases with the size of individual fires, but this is not the case for patch designs. These results agree well with recent empirical studies finding that prescribed burning has only a modest effect on subsequent unplanned fire in many biomes. They also help to explain why those empirical studies report lower effectiveness than many simulation studies. In practice, leverage values >1 (replacement of unplanned with planned fire) are hard to achieve.
... Previous assessments of the efficacy of thinning treatments in reducing fire disturbances in spotted owl habitat (Wilson and Baker 1998, Lee and Irwin 2005, Roloff et al. 2005, Ager et al. 2007, Lehmkuhl et al. 2007 have not incorporated the probability of high-severity fires occurring during the treatment lifespan. The effect of this is to overestimate treatment efficacy in potentially controlling fire or fire behavior (Rhodes and Baker 2008). Nor have the effects of recruitment of dense, late-successional forest that act to offset loss from fire been included in prior assessments. ...
... This amount is the dependent variable in our summary figures. Treatment lifespan was assumed to be 20 years (Rhodes and Baker 2008) for "one-time thinning," or maintained in perpetuity over the 40 years for "maintained." A sample calculation using the model (equation 1) is presented in the Supplementary Material. ...
... Thinning may also render adjacent, unthinned forest unsuitable or less suitable (Seamans and Gutiérrez 2007), but we did not account for this effect. The lifespan for thinning treatments that we used was 20 years for one-time thinning (Rhodes and Baker 2008), and 40 years for maintained treatments. Transition from late-to early-successional vegetation due to highseverity fire also was considered habitat loss. ...
Article
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The Northern Spotted Owl (Strix occidentalis caurina) is an emblematic, threatened raptor associated with dense, late-successional forests in the Pacific Northwest, USA. Concerns over high-severity fire and reduced timber harvesting have led to programs to commercially thin forests, and this may occur within habitat designated as "critical" for spotted owls. However, thinning is only allowed under the U.S. Government spotted owl guidelines if the long-term benefits clearly outweigh adverse impacts. This possibility remains uncertain. Adverse impacts from commercial thinning may be caused by removal of key habitat elements and creation of forests that are more open than those likely to be occupied by spotted owls. Benefits of thinning may accrue through reduction in high-severity fire, yet whether the firereduction benefits accrue faster than the adverse impacts of reduced late-successional habitat from thinning remains an untested hypothesis. We found that rotations of severe fire (the time required for high-severity fire to burn an area equal to the area of interest once) in spotted owl habitat since 1996, the earliest date we could use, were 362 and 913 years for the two regions of interest: the Klamath and dry Cascades. Using empirical data, we calculated the future amount of spotted owl habitat that may be maintained with these rates of high-severity fire and ongoing forest regrowth rates with and without commercial thinning. Over 40 years, habitat loss would be far greater than with no thinning because, under a "best case" scenario, thinning reduced 3.4 and 6.0 times more dense, late-successional forest than it prevented from burning in high-severity fire in the Klamath and dry Cascades, respectively. 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. It is also becoming increasingly recognized that exclusion of high-severity fire may not benefit spotted owls in areas where owls evolved with reoccurring fires in the landscape.
... Any approach to C accounting that assumes a wildfire burn probability of 100% during the effective life span of a fuel-reduction treatment is almost certain to overestimate the ability of such treatments to reduce pyrogenic emissions on the future landscape. Inevitably, some fraction of the land area from which biomass is thinned will not be exposed to any fire during the treatment's effective life span and therefore will incur no benefits of reduced combustion (Rhodes and Baker 2008). On the other hand, assuming that landscape-wide burn probabilities apply to all of the treated area is almost certain to underestimate the influence of treatment on future landscape combustion. ...
... Given a fuel-treatment life expectancy of 10-25 years, only 1-20% of treated areas will ever have the opportunity to affect fire behavior. Such approximations are consistent with a similar analysis reported by Rhodes and Baker (2008), who suggested that only 3% of the area treated for fuels is likely to be exposed to fire during their assumed effective life span of 20 years. Extending treatment efficacy by repeated burning of understory fuels could considerably increase the likelihood of a treated stand to affect wildfire behavior, but such efforts come at the cost of more frequent C loss. ...
Article
It has been suggested that thinning trees and other fuel-reduction practices aimed at reducing the probability of high-severity forest fire are consistent with efforts to keep carbon (C) sequestered in terrestrial pools, and that such practices should therefore be rewarded rather than penalized in C-accounting schemes. By evaluating how fuel treatments, wildfire, and their interactions affect forest C stocks across a wide range of spatial and temporal scales, we conclude that this is extremely unlikely. Our review reveals high C losses associated with fuel treatment, only modest differences in the combustive losses associated with high-severity fire and the low-severity fire that fuel treatment is meant to encourage, and a low likelihood that treated forests will be exposed to fire. Although fuel-reduction treatments may be necessary to restore historical functionality to firesuppressed ecosystems, we found little credible evidence that such efforts have the added benefit of increasing terrestrial C stocks.
... Any approach to C accounting that assumes a wildfire burn probability of 100% during the effective life span of a fuel-reduction treatment is almost certain to overestimate the ability of such treatments to reduce pyrogenic emissions on the future landscape. Inevitably, some fraction of the land area from which biomass is thinned will not be exposed to any fire during the treatment's effective life span and therefore will incur no benefits of reduced combustion (Rhodes and Baker 2008). On the other hand, assuming that landscape-wide burn probabilities apply to all of the treated area is almost certain to underestimate the influence of treatment on future landscape combustion. ...
... Given a fuel-treatment life expectancy of 10-25 years, only 1-20% of treated areas will ever have the opportunity to affect fire behavior. Such approximations are consistent with a similar analysis reported by Rhodes and Baker (2008), who suggested that only 3% of the area treated for fuels is likely to be exposed to fire during their assumed effective life span of 20 years. Extending treatment efficacy by repeated burning of understory fuels could considerably increase the likelihood of a treated stand to affect wildfire behavior, but such efforts come at the cost of more frequent C loss. ...
Article
Full-text available
It has been suggested that thinning trees and other fuel-reduction practices aimed at reducing the probability of high-severity forest fire are consistent with efforts to keep carbon (C) sequestered in terrestrial pools, and that such practices should therefore be rewarded rather than penalized in C-accounting schemes. By evaluating how fuel treatments, wildfire, and their interactions affect forest stocks across a wide range of spatial and temporal scales, we conclude that this is extremely unlikely. Our review reveals high losses associated with fuel treatment, only modest differences in the combustive losses associated with high-severity fire and the low-severity fire that fuel treatment is meant to encourage, and a low likelihood that treated forests will be exposed to fire. Although fuel-reduction treatments may be necessary to restore historical functionality to firesuppressed ecosystems, we found little credible evidence that such efforts have the added benefit of increasing terrestrial stocks.
... Fuel treatments may be applied to areas that do not subsequently experience wildfire resulting in carbon reductions from the treatment without the carbon benefit from reduced wildfire emissions. In the western US, Rhodes and Baker (2008) found an 8% chance that fuel treatments were subsequently burned by wildfire in a 20 year period. Similarly, Campbell et al. (2012) found that ten locations must be treated in order to beneficially impact future fire in just one location. ...
... Fuel treatments have been proven to reduce fire intensity and therefore severity when burned by wildfires under most weather conditions (i.e., Lyons-Tinsley and Peterson, 2012;Moghaddas and Craggs, 2007;Pollet and Omi, 2002;Safford et al., 2012). Although only a small percentage of fuel treatments are burned by wildfires (Campbell et al., 2012;Rhodes and Baker, 2008), treatments continue to be implemented due to the known benefits to aiding fire suppression resources (Moghaddas and Craggs, 2007) and reducing potential fire emissions (North and Hurteau, 2011). To date, three studies have quantified the effect of fuel treatments on carbon stocks beyond the first couple of years using empirical data (Boerner et al., 2008;Hurteau and North, 2010;Hurteau et al., 2011). ...
... A reaction to the recent increase in the intensity and frequency of wildfires is to thin forests to reduce the quantity of combustible materials. However, the amount of carbon removed by thinning is much larger than the amount that might be saved from being burned in a fire, and far more area is harvested than would actually burn [42,[46][47][48][49]. Most analyses of mid-to long-term thinning impacts on forest structure and carbon storage show there is a multi-decadal biomass carbon deficit following moderate to heavy thinning [50]. ...
Article
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This paper provides a review and comparison of strategies to increase forest carbon, and reduce species losses for climate change mitigation and adaptation in the United States. It compares forest management strategies and actions that are taking place or being proposed to reduce wildfire risk and to increase carbon storage with recent research findings. International agreements state that safeguarding biodiversity and ecosystems is fundamental to climate resilience with respect to climate change impacts on them, and their roles in adaptation and mitigation. The recent Intergovernmental Panel on Climate Change report on impacts, mitigation, and adaptation found, and member countries agreed, that maintaining the resilience of biodiversity and ecosystem services at a global scale is “fundamental” for climate mitigation and adaptation, and requires “effective and equitable conservation of approximately 30 to 50% of Earth’s land, freshwater and ocean areas, including current near-natural ecosystems.” Our key message is that many of the current and proposed forest management actions in the United States are not consistent with climate goals, and that preserving 30 to 50% of lands for their carbon, biodiversity and water is feasible, effective, and necessary for achieving them.
... A central challenge is measuring society's full valuation of resources at risk of fire. Even if values are quantifiable, there is considerable uncertainty as to how potential losses respond to various wildfire management options (Gorte and Gorte, 1979;Rhodes and Baker, 2008;Barnett et al., 2016;Ager et al., 2018). An additional challenge lies in balancing the tradeoffs inherent in managing all fire-prone lands, as when treatments to reduce fire threat also impact natural resources nearby (e.g., wildlife, water bodies) and farther off (e.g., potentially harmful smoke from prescribed burns traveling to undesired areas). ...
Article
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Wildfire is an integral part of many ecosystems, and wildland fires also have the potential for costly impacts to human health and safety, and damage to structures and natural resources. Public land managers use various strategies for managing landscape conditions that can affect wildfire, broadly: fuel treatment (and other pre-fire risk mitigation), fire suppression, and post-fire landscape rehabilitation. However, with any of these strategies there is considerable uncertainty in the outcomes that managers can obtain, and thus on the societal costs and benefits associated with wildland fire management. Managers address that uncertainty by using available information to inform their strategy choices. The value of information (VOI) to the land manager is defined as the expected gains from improved wildland fire management outcomes that result from using the information. This paper discusses estimating the value of information using two approaches: a microeconomic theoretical approach, and the Bayesian decision-tree approach frequently used in the VOI literature. These approaches could be used for valuing specific pieces of information (with absolute values), and for prioritizing (with relative values) which areas to focus on for future research.
... Moist carbon rich forests in the Pacific Coast Range and West Cascades ecoregions are projected to be the least vulnerable to either drought or fire in the future 25 , though extreme hot, dry, and windy conditions led to fires in the West Cascades in 2020. It is important to recognize that forest thinning to reduce fire risk has a low probability of success in the western US 73 , results in greater carbon losses than fire itself, and is generally not needed in moist forests [79][80][81][82] . Predicting future occurrence and timing of large disturbance events remains difficult, thus to better inform land management, efforts are needed to improve the ability of terrestrial biosphere models to simulate fire, drought, and other ecosystem processes 83,84 . ...
Article
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Forest preservation is crucial for protecting biodiversity and mitigating climate change. Here we assess current forest preservation in the western United States using spatial data and find that beyond the 18.9% (17.5 Mha) currently protected, an additional 11.1% (10.3 Mha) is needed to achieve 30% preservation by 2030 (30 × 30). To help meet this regional preservation target, we developed a framework that prioritizes forestlands for preservation using spatial metrics of biodiversity and/or carbon within each ecoregion. We show that meeting this preservation target would lead to greater protection of animal and tree species habitat, current carbon stocks, future carbon accumulation, and forests that are important for surface drinking water. The highest priority forestlands are primarily owned by the federal government, though substantial areas are also owned by private entities and state and tribal governments. Establishing Strategic Forest Reserves would help protect biodiversity and carbon for climate adaptation and mitigation.
... Recent meta-analyses of fuel treatment effectiveness demonstrate that at landscape and regional scales, fuel treatments account for only a small fraction (˜1%) of the area burned by wildfires (e.g., Barnett et al. 2016a, Kolden 2019. Therefore, there is some concern that treatments are ineffective because under current prescription levels, wildfires may not actually encounter treated areas during the duration of their potential effectiveness (Odion andHanson 2006, Rhodes andBaker 2008). While this is factually accurate at the current pace and scale of treatment in wNA, the question is not whether every wildfire can be impacted by fuels treatments, but whether treatments can be strategically used to multiply their benefits and promote greater opportunities for applying wildland fire across landscapes. ...
Article
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We review science‐based adaptation strategies for western North American (wNA) forests that include restoring active fire regimes and fostering resilient structure and composition of forested landscapes. As part of the review, we address common questions associated with climate adaptation and realignment treatments that run counter to a broad consensus in the literature. These include: (1) Are the effects of fire exclusion overstated? If so, are treatments unwarranted and even counterproductive? (2) Is forest thinning alone sufficient to mitigate wildfire hazard? (3) Can forest thinning and prescribed burning solve the problem? (4) Should active forest management, including forest thinning, be concentrated in the wildland urban interface (WUI)? (5) Can wildfires on their own do the work of fuel treatments? (6) Is the primary objective of fuel reduction treatments to assist in future firefighting response and containment? (7) Do fuel treatments work under extreme fire weather? (8) Is the scale of the problem too great – can we ever catch up? (9) Will planting more trees mitigate climate change in wNA forests? and (10) Is post‐fire management needed or even ecologically justified? Based on our review of the scientific evidence, a range of proactive management actions are justified and necessary to keep pace with changing climatic and wildfire regimes and declining forest successional heterogeneity after severe wildfires. Science‐based adaptation options include the use of managed wildfire, prescribed burning, and coupled mechanical thinning and prescribed burning as is consistent with land management allocations and forest conditions. Although some current models of fire management in wNA are averse to short‐term risks and uncertainties, the long‐term environmental, social, and cultural consequences of wildfire management primarily grounded in fire suppression are well documented, highlighting an urgency to invest in intentional forest management and restoration of active fire regimes.
... Because the size of the mean negative effect from fire on owl occupancy is less than normal annual variation in occupancy rates, many scientists would agree with us that encouraging logging or fuels reduction, with the known logging-induced negative effects on occupancy, does not seem prudent (The Wildlife Society 2010;Dugger et al. 2011;Raphael et al. 2013;Stephens et al. 2014;Lehmkuhl et al. 2015). The argument for logging to potentially reduce severity of fire that might happen in the future is further weakened when forest managers understand that fuels reduction logging activities have a very low probability of ever interacting with or influencing a forest fire (Rhodes and Baker 2008;Odion et al. 2014;Charnley et al. 2015). Conservation biology typically espouses conservatism and the precautionary principle when considering unnatural anthropogenic actions such as logging (Noss 1993). ...
Article
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In Peery et al.’s letter (2019) in Frontiers in Ecology and the Environment, we were accused of “agenda-driven” science with regard to our research pertaining to spotted owls and wildland fire (e.g., Hanson et al. 2018, Lee 2018). Peery et al. (2019) criticize us for stating our view that the current scientific evidence warrants increased protection of forests, while they advocate for their own agenda promoting commercial logging on federal lands in spotted owl habitat (Jones et al. 2016; Peery et al. 2019). We receive funding from conservation-oriented foundations which aligns with our motivations, while Perry et al. receive funding from agencies that are supportive of forestry and logging, which clearly influences their interpretations. Scientists’ points of view certainly influence their interpretations of the data as well as the types of experiments that we all conduct. This isn’t a problem as long as our disagreements and differences in interpretation are worked out in the normal scientific process of peer-reviewed publications and factually based commentary about each other’s work. Peery et al. attempted to win this debate by attacking us with false, biased, and undocumented claims, against the ethical code of the Ecological Society of America. Sadly, the journal that published the defamatory letter by Peery et al. has refused to print any rebuttal by us to correct the record. Here, we refute each of Peery et al.’s claims and include supporting documentation.
... Evaluations should include common metrics that describe fire regimes (e.g., fire frequency, fire area, fire behavior) and fire effects (e.g., fire severity, air quality) summarized over relevant scales. the encounter rate between wildfire and prescribed fire is relatively rare (Barnett et al., 2016;Rhodes and Baker, 2008), although many areas (e.g., Southeast, wildland urban interface) have been excluded from such analyses and investigators tend to find increasing encounter rates as the scale of prescribed fire increases. For this reason, it is important that any evaluation of tradeoffs between wildfire and prescribed fire regimes, especially those studies using simulation modeling, consider the probability of wildfire occurrence and spread in space and time. ...
Article
Prescribed fire can result in significant benefits to ecosystems and society. Examples include improved wildlife habitat, enhanced biodiversity, reduced threat of destructive wildfire, and enhanced ecosystem resilience. Prescribed fire can also come with costs, such as reduced air quality and impacts to fire sensitive species. To plan for appropriate use of prescribed fire, managers need information on the tradeoffs between prescribed fire and wildfire regimes. In this study, we argue that information on tradeoffs should be presented at spatial and temporal scales commensurate with the scales at which these processes occur and that simulation modeling exercises should include some realistic measure of wildfire probability. To that end, we synthesized available scientific literature on relationships between prescribed fire and wildfire regimes, and their associated ecological and societal effects, focusing specifically on simulation modeling studies that consider wildfire probability and empirical and modeling studies that consider prescribed fire and wildfire regimes at spatial and temporal scales beyond individual events. Both empirical and modeling studies overwhelmingly show that increasing use of prescribed fire can result in wildfire regimes of lower extent and intensity. In some studies, a consequence associated with increased use of prescribed fire is an increase in the total, cumulative amount of fire on a landscape over time. Presumably this has implications for emissions and ecosystem carbon, however, effects on ecosystem carbon dynamics are much less clear as results vary considerably across studies. Results likely vary because studies use various landscape models with different parameter settings for processes (e.g., vegetation succession) and use different methodologies, time frames, and fire management and climate change scenarios. Future syntheses and meta-analyses would benefit from researchers providing more comprehensive and transparent documentation of model parameters, assumptions, and limitations. The literature review also revealed that studies on the implications of prescribed fire and wildfire regimes with regard to values other than carbon and emissions are scant and this represents a critical research need. Empirical studies are needed to calibrate and provide magnitude of order comparisons with simulation models and address tradeoffs with respect to other values (e.g., wildland urban interface, wildlife habitat). Such studies should be conducted with consideration for our framework, which includes the implications of prescribed fire and wildfire across broad spatial and temporal scales.
... Fuel treatments can generate increased feedstock for Building Carbon in America's Farms, Forests, and Grasslands bioenergy operations or wood products manufacturing, but they may also result in short-term carbon declines as material is removed (Finkral and Evans 2008;Evans and Finkral 2009;North and Hurteau 2011). Long-run carbon storage may increase as the risk of catastrophic wildfire lessens (North and Hurteau 2011), but some research suggests that repeated interventions are necessary to maintain the benefits yielded by the initial fuels reduction activity (Agee and Skinner 2005;Collins et al. 2011) and that situation-specific factors can influence the response of treated areas to future fires (Rhodes and Baker 2008). Still others argue that the net carbon implications of fuels treatment may be negligible (Mitchell 2015) and that even with the bioenergy benefits stemming from removed material, an increase in maximum stand carbon storage is necessary to yield net GHG improvements through fuels treatment (Hudiburg et al. 2011;Campbell et al. 2012). ...
Technical Report
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The vegetation and soils found in landscapes across the United States serve as carbon sinks, removing an estimated 850 million metric tons of CO2e from the atmosphere each year and offsetting 16 percent of annual industrial emissions. There is significant uncertainty about the future and scale of this sink. Failure to stabilize the current sink and preserve U.S. land carbon mitigation capacity could jeopardize the effectiveness of U.S. climate change policy and the nation’s ability to meet future emissions reduction targets. To address this challenge, a consortium of organizations and experts came together to launch the Land Carbon Policy Roadmap (LCPR) initiative to develop and implement policy recommendations that ensure U.S. lands continue to significantly reduce economy-wide emissions through 2050 and to provide robust agricultural, silvicultural, and ecosystem services. This report is the first step toward developing that roadmap.
... To simplify accounting of fuel treatment effects, we assume fuel treatments will be implemented immediately and have a constant effectiveness for 25 years. The longevity of fuel treatments is not well constrained, but a similar analysis assumed fuel treatments are effective for 20 years in the western USA (Rhodes and Baker 2008). We lengthened the effective longevity to 25 years for the present study owing to lower forest productivity in the study area (Peet 1981) and results of a stand dynamics modelling study, which suggest forest thinning should reduce torching for ,20 years and active crown fire for ,40 years ) at the locally observed regeneration density following forest thinning (Francis et al. 2018). ...
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Recent research in the central Amazon suggests that wind is a major agent of disturbance, however, a mechanistic understanding of how wind may lead to tree mortality in Amazonian forests remains unclear. Here we estimated wind speeds necessary to topple central Amazon trees by linking both static and dynamic versions of two wind speed estimation methods (four methods total) to field data on tree failure derived from a static winching study. Static versions of these methods assumed invariant wind characteristics as more trees failed, while dynamic versions updated tree spacing, leaf area index and wind profiles progressively after each tree failure. First, we used a profile method which estimates wind force on individual trees by segments. We calculated drag on each segment and converted drag into basal turning moment, and compared the summed turning moments to the critical turning moment measured in the winching study. Estimated critical wind speeds from the static profile method varied greatly, from 10.75 m s−1 to >120.0 m s−1 with a mean of 45.70 m s−1. Critical wind speeds estimated with static approaches decreased with tree size but were not significantly different between two focal genera. Primary drivers of variation in critical wind speed were tree height and crown size. Second, we used the turning moment coefficient method of Hale, S.E., Gardiner, B., Peace, A., Nicoll, B., Taylor, P. and Pizzirani, S. 2015 Comparison and validation of three versions of a forest wind risk model. Environ. Model. Softw.68, 27–41. doi:10.1016/j.envsoft.2015.01.016.; the static version of this method yielded less-variable estimates, ranging from 18.98 to 52.01 m s−1, with a mean of 30.88 m s−1. Notably, the two static methods for estimating critical wind speeds differed in the trees they identified as having the highest and lowest critical wind speeds. Dynamic variants of the above two methods produced greatly reduced ranges in CWS estimates for our study trees, because after the early tree failures, remaining trees were subject to greater wind penetration into the stand and thus greater loading for a given above-canopy wind speed. CWS estimated with dynamic approaches differed significantly between the focal taxa. Nevertheless, both estimates suggest that wind speeds commonly observed during Amazon storms are sufficient to produce widespread tree damage and mortality.
... To simplify accounting of fuel treatment effects, we assume fuel treatments will be implemented immediately and have a constant effectiveness for 25 years. The longevity of fuel treatments is not well constrained, but a similar analysis assumed fuel treatments are effective for 20 years in the western USA (Rhodes and Baker 2008). We lengthened the effective longevity to 25 years for the present study owing to lower forest productivity in the study area (Peet 1981) and results of a stand dynamics modelling study, which suggest forest thinning should reduce torching for ,20 years and active crown fire for ,40 years ) at the locally observed regeneration density following forest thinning (Francis et al. 2018). ...
Article
Concerns over wildfire impacts to water supplies have motivated efforts to mitigate risk by reducing forest fuels. Methods to assess fuel treatment effects and prioritise their placement are needed to guide risk mitigation efforts. We present a fuel treatment optimisation model to minimise risk to multiple water supplies based on constraints for treatment feasibility and cost. Risk is quantified as the expected sediment impact costs to water supplies by combining measures of fire likelihood and behaviour, erosion, sediment transport and water supply vulnerability. We demonstrate the model's utility for prioritising fuel treatments in two large watersheds in Colorado, USA, that are critical for municipal water supply. Our results indicate that wildfire risk to water supplies can be substantially reduced by treating a small portion of the watersheds that have dense, fire-prone forests on steep slopes that drain to water supply infrastructure. Our results also show that the cost of fuel treatments outweighs the expected cost savings from reduced sediment inputs owing to the low probability of fuel treatments encountering wildfire and the high cost of thinning forests. This highlights the need to expand use of more cost-effective treatments, like prescribed fire, and to identify fuel treatment projects that benefit multiple resources.
... A variety of fuel treatments have been promoted as a means of restoring fire-dependent forests to conditions that better resemble historical and healthy conditions that existed prior to long-term fire suppression [16][17][18][19][20]. However, several experts point out that it may not be financially, politically, and/or physically feasible to decrease fuel loads enough to significantly reduce wildfire losses [12,21,22]. ...
Article
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This study develops a conceptual framework for evaluating the sensitivity of the ranking of forest fuel treatment strategies (FTSs) to variation in managers’ risk attitudes and the importance ratings managers assign to fuel treatment objectives and demonstrates the application of the framework using a case study. The conceptual framework involves (1) defining a utility function on an index that is a weighted average of fuel treatment objectives and incorporates a manager’s risk attitude; (2) using the utility function to calculate utility values for FTSs; (3) applying the stochastic efficiency with respect to a function method to utility values to obtain certainty equivalents (CEs); and (4) ranking FTSs based on statistically significant differences in median CEs for pairs of FTSs. The case study involves three (federal, state, and private) forested areas in Flathead County, Montana, USA, three FTSs (i.e., Community Wildfire Protection Plan (CWPP) Priority; CWPP & Wildland-Urban Interface Priority; and No Priority), three treatment objectives (i.e., minimizing expected residential monetary losses from wildfire, minimizing expected deviation of forest ecological conditions from their historic range and variability, and maximizing expected net returns from timber harvesting associated with fuel treatment), two risk attitudes (i.e., almost risk neutral and highly risk averse), and 35 weight scenarios for treatment objectives. Case study results are used to test the hypothesis that the ranking of FTSs is sensitive to manager’s risk attitudes and the importance ratings for management objectives. The ranking of FTSs for the three forested areas was insensitive for an almost risk neutral manager and sensitive for a highly risk averse manager. In general, the case study indicates that the ranking of FTSs is sensitive to both a forest manager’s risk attitudes and the importance ratings assigned to fuel treatment objectives.
... Several factors may determine the degree to which fuel treatments are effective in reducing the size and severity of wildfires: the type and intensity of the treatment (i.e., how much biomass is removed and how slash is managed; ), the spatial placement and configuration of fuel treatments across the landscape (Kim et al. 2009, Duncan et al. 2015, the time since treatment (Rhodes and Baker 2008), and the weather conditions at the time of a fire (e.g., wind speed and direction, relative humidity, recent precipitation amounts; Gedalof et al. 2005, Stephens et al. 2012. During extreme weather conditions, fuel treatments are less effective at the site level because of the overriding effect of strong winds, low precipitation, low relative humidity, and rapid drying times of fuel beds (Gedalof et al. 2005, Krawchuk and Moritz 2011). ...
Thesis
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... The primary goal of natural resource management is to ensure the sustainable provision of market and non-market ecosystem goods and services to satisfy the current and future needs of the growing population. Managers often have to strike a careful balance between various competing uses of natural endowments and to ensure that ecosystems perform environmental functions; thus accounting for tradeoffs and synergies among management objectives takes on critical importance (Tóth et al. 2006;Seidl et al. 2007;Nelson et al. 2009;Tóth and McDill 2009;Calkin et al. 2005;Lehmkuhl et al. 2007;Kennedy et al. 2008;Rhodes and Baker 2008;Schroder et al. 2016;Rabotyagov et al. 2016a). Existing research shows the importance of identifying tradeoffs and synergies for decision making in land use and restoration projects planning and implementation. ...
Article
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Wetland restoration can increase the provision of multiple non-market ecosystem services. Environmental and socio-economic factors need to be accounted for when land is withdrawn from agriculture and wetlands are restored. We build multi-objective optimization models to provide decision support for wetland restoration in the Le Sueur river watershed in Southern Minnesota. We integrate environmental objectives of sediment reduction and habitat protection with socio-economic factors associated with the overlap of private land with potential wetland restoration sites in the watershed and the costs representing forward-looking farmers voluntarily taking land out of agricultural production in favor of wetland restoration. Our results demonstrate that the inclusion of these factors early on in the restoration planning process affects both the total costs of the restoration project and the spatial distribution of optimally selected wetland restoration sites.
... Although climate change plays an undeniable role in this increase (Westerling et al 2006, Rhodes and Baker 2008, Preisler et al 2011, Miller and Safford 2012, Berner et al 2017, its exact contribution is unclear. Factors such as firefighting, vegetation management, and land ownership are known to impact fire in complex ways (Westerling and Bryant 2008, Miller et al 2012a, Barbero et al 2014, Parks et al 2016, though there is limited research on the role each plays in influencing fire probability. ...
Article
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The extent of wildfires in the western United States is increasing, but how land ownership, firefighting, and reserve status influence fire probability is unclear. California serves as a unique natural experiment to estimate the impact of these factors, as ownership is split equally between federal and non-federal landowners; there is a relatively large proportion of reserved lands where extractive uses are prohibited and fire suppression is limited; and land ownership and firefighting responsibility are purposefully not always aligned. Panel Poisson regression techniques and pre-regression matching were used to model changes in annual fire probability from 1950–2015 on reserve and non-reserve lands on federal and non-federal ownerships across four vegetation types: forests, rangelands, shrublands, and forests without commercial species. Fire probability was found to have increased over time across all 32 categories. A marginal effects analysis showed that federal ownership and firefighting was associated with increased fire probability, and that the difference in fire probability on federal versus non-federal lands is increasing over time. Ownership, firefighting, and reserve status, played roughly equal roles in determining fire probability, and were found to have much greater influence than average maximum temperature (°C) during summer months (June, July, August), average annual precipitation (cm), and average annual topsoil moisture content by volume, demonstrating the critical role these factors play in western fire regimes and the importance of including them in future analysis focused on understanding and predicting wildfire in the Western United States.
... However, treatment options can be severely constrained or economically unviable in some landscapes, and questions persist regarding return on investment given current scales of treatment and the relative rarity of fire [32][33][34][35][36]. Expanding the footprint of treated areas and being more strategic in the choice of where to implement treatments are two key themes for improving treatment efficacy [37][38][39]. ...
Article
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The primary theme of this study is the cost-effectiveness of fuel treatments at multiple scales of investment. We focused on the nexus of fuel management and suppression response planning, designing spatial fuel treatment strategies to incorporate landscape features that provide control opportunities that are relevant to fire operations. Our analysis explored the frequency and magnitude of fire-treatment encounters, which are critical determinants of treatment efficacy. Additionally, we examined avoided area burned, avoided suppression costs, and avoided damages, and combined all three under the umbrella of leverage to explore multiple dimensions with which to characterize return on investment. We chose the Sierra National Forest, California, USA, as our study site, due to previous work providing relevant data and analytical products, and because it has the potential for large, long-duration fires and corresponding potential for high suppression expenditures. Modeling results generally confirmed that fire-treatment encounters are rare, such that median suppression cost savings are zero, but in extreme years, savings can more than offset upfront investments. Further, reductions in risk can expand areas where moderated suppression response would be appropriate, and these areas can be mapped in relation to fire control opportunities.
... For these reasons, forest fuel treatment has been promoted as a public policy priority for addressing the growing risk to humans from wildfire (H. R. 1904-Healthy Forests Restoration Act of 2003, Rhodes and Baker 2008. ...
Article
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Preferred fuel treatment strategies (FTSs) were determined for two public forests in Flathead County, Montana, for the period 2010–59 using a multiple-objective evaluation method that accounts for future residential development in the WUI and climate change. Three fuel management objectives were used to evaluate and rank FTSs: minimizing monetary residential losses due to wildfire, minimizing deviation from historical forest ecological conditions, and maximizing net revenue from timber harvesting associated with fuel treatment. Preferred FTSs varied across planning periods for both forests. For the Flathead National Forest, managed by the US Forest Service, there was a unique preferred FTS for each subperiod. For the forest managed by the Montana Department of Natural Resources and Conservation, two spatially prioritized FTSs were equally preferred in period 1, one spatially prioritized FTS was preferred in subperiod 2, no spatially prioritized FTS was preferred in periods 3 and 4, and the three FTSs were equally preferred in period 5. Results suggest that evaluating FTSs for a forest on the basis of a single management objective could give misleading results about the most preferred FTS and that targeting fuel treatments based on spatial priorities may not be superior to random allocation of fuel treatments to eligible stands.
... Some studies, such as that by Hurteau and North (2010), suggested that carbon emitted from prescribed fires would be sequestered by boosted growth of trees and shrubs within a time period shorter than the historic mean fire return interval due to a carbon fertilization effect. However, others indicate that the probability of a wildfire occurring in a treated stand during the span of treatment longevity is negligible, negating any potential reduction in net emissions (Rhodes and Baker, 2008;Campbell et al., 2012;North et al., 2009). While our research provides information regarding biomass accumulation in the Northern Rockies, future enquiry should incorporate regional disturbance regimes into analysis of potential emissions tradeoffs. ...
Article
Fuel treatments in ponderosa pine forests of the northern Rocky Mountains are commonly used to modify fire behavior, but it is unclear how different fuel treatments impact the subsequent production and distribution of aboveground biomass, especially in the long term. This research evaluated aboveground biomass responses 23 years after treatment in two silvicultural installations with different cutting and underburning prescriptions in western Montana. The thinning installation included control (no treatment), thin/no burn, thin/spring burn, and thin/fall burn treatments. The shelterwood installation included control, cut/no burn, cut/wet burn, and cut/dry burn treatments. Across all fuel treatments in both the thinning and shelterwood installations, tree biomass had recovered to pre-harvest levels by 2015, or 23 years post-treatment. In the thinning, total aboveground and live-tree biomass were greatest in the control, but did not differ among the three thinned fuel treatments. Forest floor biomass was lower in the two burned treatments relative to the two unburned treatments. Seedling, vegetation, stump, and snag biomass did not differ among the four treatments. In the shelterwood, total aboveground and live tree biomass were both greater in the unburned treatments relative to the burned treatments. Forest floor and snag biomass also tended to be lower in the burned treatments. Seedling, vegetation, and stump biomass were similar across all treatments. This research shows that tree biomass in ponderosa pine stands subjected to common fuels treatments can recover to pre-harvest levels in less than 23 years, while still exhibiting reduced stand densities that promote forest restoration objectives. Burgeoning biomass at the seedling layer suggests that additional understory treatments are necessary in order to abate ladder fuel development and sustain resistance to high-severity wildfire.
... At landscape scales, where fuel treatments are considered most important [17], the proportion of landscape area that must be treated to be effective can be a significant limitation, even when applying strategic approaches that leverage greater overall effects [39,40]. An additional complication is that fuel accumulation and vegetation growth following treatment tends to reduce treatment effectiveness over time [41]; in many cases this window of opportunity may pass before a treatment is tested by a fire [42,43]. Other studies suggest that fuel treatments are less effective under more extreme weather conditions [44]. ...
Article
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Landscape heterogeneity shapes species distributions, interactions, and fluctuations. Historically, in dry forest ecosystems, low canopy cover and heterogeneous fuel patterns often moderated disturbances like fire. Over the last century, however, increases in canopy cover and more homogeneous patterns have contributed to altered fire regimes with higher fire severity. Fire management strategies emphasize increasing within-stand heterogeneity with aggregated fuel patterns to alter potential fire behavior. Yet, little is known about how such patterns may affect fire behavior, or how sensitive fire behavior changes from fuel patterns are to winds and canopy cover. Here, we used a physics-based fire behavior model, FIRETEC, to explore the impacts of spatially aggregated fuel patterns on the mean and variability of stand-level fire behavior, and to test sensitivity of these effects to wind and canopy cover. Qualitative and quantitative approaches suggest that spatial fuel patterns can significantly affect fire behavior. Based on our results we propose three hypotheses: (1) aggregated spatial fuel patterns primarily affect fire behavior by increasing variability; (2) this variability should increase with spatial scale of aggregation; and (3) fire behavior sensitivity to spatial pattern effects should be more pronounced under moderate wind and fuel conditions.
... However, when years with extreme area of fire are considered, the effects of current management and accelerated restoration were larger compared https://www.ecologyandsociety.org/vol22/iss1/art25/ to no management on federal lands. Years with extremely high fire area would have more fire-fuel treatment encounters than in years with less fire, making higher fuel treatment scenarios more effective during those years (Rhodes and Baker 2008, Barros et al. 2017. Considering only extreme fire years, the variation in amount of high-severity fire among the scenarios was quite large, and distributions of high-severity fire overlapped among the scenarios. ...
... We did not explicitly analyze optimal arrangement of fuel treatments for reducing fuel spread, and our finding that~50% area should be treated to maximize ROI relates to the area needed to reduce erosion and sediment delivery. Our model did not incorporate forest dynamics such as fuel treatment longevity (Rhodes and Baker, 2008) or post-fire recovery since we did not explicitly incorporate a time dimension. Future models estimating ROI would benefit from adding in a decline in fuel treatment effectiveness over time. ...
Article
A small but growing number of watershed investment programs in the western United States focus on wildfire risk reduction to municipal water supplies. This paper used return on investment (ROI) analysis to quantify how the amounts and placement of fuel treatment interventions would reduce sediment loading to the Strontia Springs Reservoir in the Upper South Platte River watershed southwest of Denver, Colorado following an extreme fire event. We simulated various extents of fuel mitigation activities under two placement strategies: (a) a strategic treatment prioritization map and (b) accessibility. Potential fire behavior was modeled under each extent and scenario to determine the impact on fire severity, and this was used to estimate expected change in post-fire erosion due to treatments. We found a positive ROI after large storm events when fire mitigation treatments were placed in priority areas with diminishing marginal returns after treating >50e80% of the forested area. While our ROI results should not be used prescriptively they do show that, conditional on severe fire occurrence and precipitation, investments in the Upper South Platte could feasibly lead to positive financial returns based on the reduced costs of dredging sediment from the reservoir. While our analysis showed positive ROI focusing only on post-fire erosion mitigation, it is important to consider multiple benefits in future ROI calculations and increase monitoring and evaluation of these benefits of wildfire fuel reduction investments for different site conditions and climates.
... However, when years with extreme area of fire are considered, the effects of current management and accelerated restoration were larger compared to no management on federal lands. Years with extremely high fire area would have more fire-fuel treatment encounters than in years with less fire, making higher fuel treatment scenarios more effective during those years (Rhodes and Baker 2008, Barros et al. 2017). Considering only extreme fire years, the variation in amount of high-severity fire among the scenarios was quite large, and distributions of high-severity fire overlapped among the scenarios. ...
Article
Full-text available
Fire-prone landscapes present many challenges for both managers and policy makers in developing adaptive behaviors and institutions. We used a coupled human and natural systems framework and an agent-based landscape model to examine how alternative management scenarios affect fire and ecosystem services metrics in a fire-prone multiownership landscape in the eastern Cascades of Oregon. Our model incorporated existing models of vegetation succession and fire spread and information from original empirical studies of landowner decision making. Our findings indicate that alternative management strategies can have variable effects on landscape outcomes over 50 years for fire, socioeconomic, and ecosystem services metrics. For example, scenarios with federal restoration treatments had slightly less high-severity fire than a scenario without treatment; exposure of homes in the wildland-urban interface to fire was also slightly less with restoration treatments compared to no management. Treatments appeared to be more effective at reducing high-severity fire in years with more fire than in years with less fire. Under the current management scenario, timber production could be maintained for at least 50 years on federal lands. Under an accelerated restoration scenario, timber production fell because of a shortage of areas meeting current stand structure treatment targets. Trade-offs between restoration outcomes (e.g., open forests with large fire-resistant trees) and habitat for species that require dense older forests were evident. For example, the proportional area of nesting habitat for northern spotted owl (Strix occidentalis) was somewhat less after 50 years under the restoration scenarios than under no management. However, the amount of resilient older forest structure and habitat for white-headed woodpecker (Leuconotopicus albolarvatus) was higher after 50 years under active management. More carbon was stored on this landscape without management than with management, despite the occurrence of high-severity wildfire. Our results and further applications of the model could be used in collaborative settings to facilitate discussion and development of policies and practices for fire-prone landscapes.
... Estimated historical PMFI/FR mean rates are relevant, because many ecological processes and structures change across a narrow range in rates. In the roughly 86% forests with PMFI/ FR ! 25 years, fuels that required about 7-25 years to build back up after a low-severity fire [12][13][14]. would, on average, have been fully recovered for an extended period before the next fire. Shrubs would likely have been able to fully recover and dominate for substantial periods. ...
Article
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Low-severity fires that killed few canopy trees played a significant historical role in dry forests of the western USA and warrant restoration and management, but historical rates of burning remain uncertain. Past reconstructions focused on on dating fire years, not measuring historical rates of burning. Past statistics, including mean composite fire interval (mean CFI) and individual-tree fire interval (mean ITFI) have biases and inaccuracies if used as estimators of rates. In this study, I used regression, with a calibration dataset of 96 cases, to test whether these statistics could accurately predict two equivalent historical rates, population mean fire interval (PMFI) and fire rotation (FR). The best model, using Weibull mean ITFI, had low prediction error and R²adj = 0.972. I used this model to predict historical PMFI/FR at 252 sites spanning dry forests. Historical PMFI/FR for a pool of 342 calibration and predicted sites had a mean of 39 years and median of 30 years. Short (< 25 years) mean PMFI/FRs were in Arizona and New Mexico and scattered in other states. Long (> 55 years) mean PMFI/FRs were mainly from northern New Mexico to South Dakota. Mountain sites often had a large range in PMFI/FR. Nearly all 342 estimates are for old forests with a history of primarily low-severity fire, found across only about 34% of historical dry-forest area. 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. Historical fuels (e.g., understory shrubs and small trees) could fully recover between multidecadal fires, allowing some denser forests and some ecosystem processes and wildlife habitat to be less limited by fire. Lower historical rates mean less restoration treatment is needed before beginning managed fire for resource benefits, where feasible. Mimicking patterns of variability in historical low-severity fire regimes would likely benefit biological diversity and ecosystem functioning.
... However, the relationship between forest density/fuel, mechanical fuel treatment, and fire severity is complex. For instance, thinning without subsequent prescribed fire has little effect on fire severity (see Kalies and yocum Kent 2016) and, in some cases, can increase fire severity (Raymond and Peterson 2005, Ager et al. 2007, Wimberly et al. 2009) and tree mortality (see, e.g., Stephens andMoghaddas 2005, Stephens 2009: Figure 6)-the effects depend on the improbable co-occurrence of reduced fuels (generally a short time line, within a decade or so) and wildfire activity (Rhodes and Baker 2008) and can be over-ridden by extreme fire weather (Bessie and Johnson 1995, Hély et al. 2001, Schoennagel et al. 2004, Lydersen et al. 2014. Empirical data from actual fires also indicate that postfire logging can increase fire severity in reburns (Thompson et al. 2007), despite removal of woody biomass (tree trunks) described by land managers as forest fuels (Peterson et al. 2015). ...
Article
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There is a widespread view among land managers and others that the protected status of many forestlands in the western United States corresponds with higher fire severity levels due to historical restrictions on logging that contribute to greater amounts of biomass and fuel loading in less intensively managed areas, particularly after decades of fire suppression. This view has led to recent proposals-both administrative and legislative-to reduce or eliminate forest protections and increase some forms of logging based on the belief that restrictions on active management have increased fire severity. We investigated the relationship between protected status and fire severity using the Random Forests algorithm applied to 1500 fires affecting 9.5 million hectares between 1984 and 2014 in pine (Pinus ponderosa, Pinus jeffreyi) and mixed-conifer forests of western United States, accounting for key topographic and climate variables. 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. Our results suggest a need to reconsider current overly simplistic assumptions about the relationship between forest protection and fire severity in fire management and policy.
... A management emphasis directed toward altering conditions in and immediately adjacent to human communities is very different from an emphasis directed toward treating massive amounts of fuel on more remote public lands. Fuel treatment efforts more distant from human communities may carry the negative ecological consequences we outlined earlier and do little to stop or mitigate the effects of fires that are increasingly weather driven (Rhodes and Baker 2008. ...
Article
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We use the historical presence of high-severity fire patches in mixed-conifer forests of the western United States to make several points that we hope will encourage development of a more ecologically informed view of severe wildland fire effects. First, many plant and animal species use, and have sometimes evolved to depend on, severely burned forest conditions for their persistence. Second, evidence from fire history studies also suggests that a complex mosaic of severely burned conifer patches was common historically in the West. Third, to maintain ecological integrity in forests born of mixed-severity fire, land managers will have to accept some severe fire and maintain the integrity of its aftermath. Lastly, public education messages surrounding fire could be modified so that people better understand and support management designed to maintain ecologically appropriate sizes and distributions of severe fire and the complex early-seral forest conditions it creates.
... The stochastic and variable nature of fires, the relatively fine scale over which fuels treatments are implemented, and potentially high carbon costs to implement them suggest that fuel treatments are not an effective method for protecting carbon stocks at a stand level (Reinhardt et al., 2008;Reinhardt and Holsinger, 2010). For example, in fire-prone forests of the western US, because of the relative rarity of large wildfires and limited spatial scale of treatments, most treated areas will not be exposed to wildfire within the 10-25 year life expectancy of the treatment (Rhodes and Baker, 2008;Campbell et al., 2012;North et al., 2012). Further, some studies show that the difference in carbon emissions between low-severity and high-severity fire is small when scaled across an entire wildfire because consumption of fine surface fuels associated with low-severity fire occurs across broad spatial extents, while consumption of standing fuels associated with high-severity fires occurs in small patches within the larger wildfire perimeter (Campbell et al., 2012). ...
Article
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Wildfires are an important component of the terrestrial carbon cycle and one of the main pathways for movement of carbon from the land surface to the atmosphere. Fires have received much attention in recent years as potential catalysts for shifting landscapes from carbon sinks to carbon sources. Unless structural or functional ecosystem shifts occur, net carbon balance in fire-adapted systems at steady state is zero when assessed over the entire post-fire successional sequence and at landscape scales. When evaluated at fine spatial scales and over short periods of time, however, wildfires may seem to release more carbon to the atmosphere than remains on site. Measurements of wildfire carbon emissions are thus highly biased by the spatial and temporal scales that bound them, and may over- or under-estimate carbon source-sink dynamics that provide critical feedbacks to the climate system. This synthesis paper provides a description of the ecological drivers of wildfires and carbon in forested ecosystems across the spatial and temporal scales at which system drivers (e.g., climate, weather), behaviors (e.g., wildfire occurrence, spread, intensity), and resulting patterns (e.g., vegetation composition and structure, carbon emissions) occur and interact. Improved understanding of these relationships is critical if we are to anticipate and respond to major changes in the global earth system expected in the coming decades and centuries.
... One of the concerns over fuel treatment efficacy is that, for treatments to be effective, they must overlap with fires (which occur stochastically across space) (Rhodes and Baker 2008). Treating more area (i.e., 8% vs. 4% per 5-year time step) increases the probability that a spreading fire will encounter a treatment location. ...
Article
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Research in the Sierra Nevada range of California, USA, has provided conflicting results about current trends of high-severity fire. Previous studies have used only a portion of available fire severity data, or considered only a portion of the Sierra Nevada. Our goal was to investigate whether a trend in fire severity is occurring in Sierra Nevada conifer forests currently, using satellite imagery. We analysed all available fire severity data, 1984-2010, over the whole ecoregion and found no trend in proportion, area or patch size of high-severity fire. The rate of high-severity fire has been lower since 1984 than the estimated historical rate. Responses of fire behaviour to climate change and fire suppression may be more complex than assumed. A better understanding of spatiotemporal patterns in fire regimes is needed to predict future fire regimes and their biological effects. Mechanisms underlying the lack of an expected climate-and time since fire-related trend in high-severity fire need to be identified to help calibrate projections of future fire. The effects of climate change on high-severity fire extent may remain small compared with fire suppression. Management could shift from a focus on reducing extent or severity of fire in wildlands to protecting human communities from fire.
... An often-cited critique of fuels treatments is that the probability of wildfire burning a treated area within the expected lifespan of the treatment is so low that treatment costs and potential impacts on forest resources (e.g., carbon, watercourses, etc.) are rarely justified (Rhodes andBaker 2008, Campbell et al. 2011). Indeed, in California fuels treatments designed for the suppression and containment of wildfire may rarely be economical except in the WUI or areas with known high ignition probabilities (i.e., road corridors). ...
Article
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The USDA Forest Service is implementing a new planning rule and starting to revise forest plans for many of the 155 National Forests. In forests that historically had frequent fire regimes, the scale of current fuels reduction treatments has often been too limited to affect fire severity and the Forest Service has predominantly focused on suppression. In addition to continued treatment of the wildland urban interface, increasing the scale of low- and moderate-severity fire would have substantial ecological and economics benefits if implemented soon. We suggest National Forests identify large contiguous areas to concentrate their fuels reduction efforts, and then turn treated firesheds over to prescribed and managed wildfire for future maintenance. A new round of forest planning provides an opportunity to identify and overcome some of the current cultural, regulatory, and institutional barriers to increased fire use that we discuss.
... Although there are many examples of fuel treatments reducing fire behaviour when conditions are not extreme, recently treated forests can experience a stand-replacing crown fire when wind speeds exceed 30 km h −1 and when fuel moisture is low 102 . When the probability of fire occurring in a particular area is relatively low, the odds of a fuel treatment influencing the behaviour of a wildfire there, within the time frame that treatments are effective, is also low 103 . The degree of protection provided by a particular mechanical treatment may thus depend on uncertain parameters (for example, ignition patterns and extreme wind frequencies). ...
Article
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The impacts of escalating wildfire in many regions — the lives and homes lost, the expense of suppression and the damage to ecosystem services — necessitate a more sustainable coexistence with wildfire. Climate change and continued development on fire-prone landscapes will only compound current problems. Emerging strategies for managing ecosystems and mitigating risks to human communities provide some hope, although greater recognition of their inherent variation and links is crucial. Without a more integrated framework, fire will never operate as a natural ecosystem process, and the impact on society will continue to grow. A more coordinated approach to risk management and land-use planning in these coupled systems is needed.
... The sometimes dramatic short-term effects of fire and postfire disturbance on stream channels, water quality, and mortality of individual organisms can be readily apparent. As a result, attempts to influence fire and its effects on aquatic systems and fish populations before and, particularly, during and after the fire, have consumed considerable resources, time, and energy, and engendered substantial debate (e.g., Dunham and others 2003;Rieman and others 2003;NMFS 2007;Rhodes and Baker 2008;Rieman and others 2010). ...
... For western North American forests in uplands the literature is replete with ambiguous and conflicting results regarding the effects of thinning and other mechanical fuels treatments on fire severity, rate of spread, and recurrence. Moreover, the probability of a fire burning through a treated stand within the limited time window of potential effectiveness of a fuels treatment has been shown to be very small (Lydersen et al. 2014, Rhodes andBaker 2008). Any presumed benefit is even less persistent in Riparian Reserve areas where woody vegetation regrows rapidly after treatment, and where in moister forest types fire tends to recur with lower frequency. ...
Technical Report
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Twenty years have elapsed since a major science synthesis and planning effort led to adoption of the Aquatic Conservation Strategy (ACS) of the Northwest Forest Plan (NFP) in 1994. Their purpose was to protect and restore riparian and aquatic ecosystems on Pacific Northwest federal forest lands and to ensure that forest management plans achieved legally required and socially desired multiple use objectives, including protection of water quality, aquatic and wildlife resources. In this paper, we review relevant science emerging since 1993 to assess whether proposed changes to the ACS, including reduced riparian reserve protections and a substantially lowered burden of proof for watershed-disturbing activities, are scientifically justified. Observed and anticipated effects of climate change, and of cumulative anthropogenic stressors operating in the nonfederal lands surrounding NFP lands strongly indicate the need to strengthen, not weaken key ACS protections. Roads and ground disturbance associated with mechanical thinning and fuels reduction activities, especially within Riparian Reserves, cause adverse environmental impacts that generally offset or exceed presumed restorative benefits. Headwater streams warrant wider riparian forest buffers than current ACS provisions to ensure effective retention of sediment and nutrients derived from upslope logging, fire, and landslides. Widespread and sustained ecological harm caused by roads is now widely recognized, and ACS measures should be strengthened to more effectively arrest and reduce road impacts in all catchments. Grazing, mining, post-disturbance logging (e.g., fire salvage), water withdrawal, and aerial application of toxic chemicals can cause both acute and chronic harm to aquatic ecosystems. Existing ACS standards and guidelines would need to be strengthened to more effectively control these impacts. A more thorough and current scientific review and synthesis by federal agencies to inform a future ACS is long overdue. Unfortunately, no such review has occurred, while recent agency and legislative proposals would substantially reduce protective provisions of the ACS and NFP by increasing the extent of logging and other mechanized forest management, such as fuels treatments.
... Although the C balance depends on forest type, these (Hurteau and North 2009;Mitchell et al. 2009). Given the low probability of high-severity wildfire occurring at most forest locations Rhodes and Baker 2008), thinning a forest to reduce the risk of C loss may not "pencil out" as a net C gain from a global perspective. However, what may appear to be a very low risk from a global perspective may be perceived quite differently by a C registry. ...
Article
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A forest carbon (C) offset is a quantifiable unit of C that is commonly developed at the local or regional project scale and is designed to counterbalance anthropogenic C emissions by sequestering C in trees. In cap-and-trade programs, forest offsets have market value if the sequestered C is additional (more than would have occurred in the absence of the project) and permanent (sequestered within the project boundary for a specified period of time). Local management and ecological context determine the rate of C sequestration, risk of loss, and hence the market value. An understanding of global C dynamics can inform policy but may not be able to effectively price an ecosystem service, such as C sequestration. Appropriate pricing requires the assistance of ecologists to assess C stock abundance and stability over spatial and temporal scales appropriate for the regional market. We use the risk that sequestered C will be emitted as a result of wildfire (reversal risk) to show how ecological context can influence market valuation in offset programs.
... Properly balancing multiple landscape management objectives, including activity implementation (e.g., treatment location) and understanding feedbacks with ecosystem C dynamics (e.g., Daugherty and Fried, 2007;Rhodes and Baker, 2008;Schmidt et al., 2008), requires more information about their inherent trade-offs, and improved awareness of the opportunities for optimizing management at the landscape scale (Syphard et al., 2011). The strategic placement of fuel treatments is important for reducing landscape level wildfire spread and intensity (Finney et al., 2008;Schmidt et al., 2008) and therefore understanding where treatments may be most effective may be more important than the amount of area treated. ...
... We also presupposed that the effects of management history on fire sizes along the wilderness gradient would be evident in certain places where multiple fires were limited in size due to reduced fuels in older, adjacent burned areas (Finney et al. 2007, Rhodes andBaker 2008). These situations are more likely to occur in systems where fuel treatments have been shown to be most effective in limiting fire size and/or severe effects (Schoennagel and Nelson 2010), for example, mixed-conifer ecosystems of the Sierra Nevada (Keifer et al. 2006). ...
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In many U. S. federally designated wilderness areas, wildfires are likely to burn of their own accord due to favorable management policies and remote location. Previous research suggested that limitations on fire size can result from the evolution of natural fire regimes, specifically in places where fuels were recently reduced by previous burning. To explore the broader-scale importance of fire management on wilderness landscapes, we selected three study regions representing diverse ecosystems in the western U. S. and modeled the change in fire size distributions across a gradient defined by wilderness/non-wilderness boundaries. For randomly selected locations across the gradient, we derived a scaling parameter (alpha) using fire size-frequency data for public lands (1984-2007); the parameter reflected the magnitude of change in the right tail of the fire size distribution where the largest fires reside. We then used quantile regression to model changes in a across the wilderness gradient, interpreting the results in terms of constraints on the relative role of large fires in structuring the fire size distribution. In the Southwest study region, the influence of large fires on size distributions decreased across the gradient toward wilderness at some places, suggesting that increased occurrence of natural burning, favored by wilderness management, led to limitations on fire sizes within recent timeframes. In contrast, we were unable to support the expectation that wilderness fire management limits the role of large fires in the Sierra Nevada and Northern Rockies study regions. Rather, the predominance of large fires increased toward wilderness interiors. Among spatial climate and topographic roughness variables included in our study, only winter and fire season precipitation limited fire size in the Northern Rockies, whereas several constraints on large fire occurrence operated in other regions. In southwestern ecosystems, evidence is needed to document stability in fire size distributions through time. In ecosystems of the Sierra Nevada and Northern Rockies, a longer temporal extent of observations may better match scales of disturbance and recovery. Our findings reflect the role of wilderness in addressing a fire deficit which has resulted from strong human influences on forests and fires over the past 150 years.
... No direct historical comparison could be made between current and historical highseverity rotations in the Klamath and northern Rockies at the spatial scale required in Table 4, but evidence presented in Table S1 suggests that current rotations of 599 years and 500 years, respectively, may be longer. The estimated rotation of 625 years for recent high-severity fire in the southwestern USA [92] was shorter than the historical estimate of 828 years for the Mogollon Plateau in Arizona. Combining the Mogollon Plateau and Black Mesa to provide a better comparison with fire across the southwestern USA produces a historical high-severity rotation of 522 years [57]. ...
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There is widespread concern that fire exclusion has led to an unprecedented threat of uncharacteristically severe fires in ponderosa pine (Pinus ponderosa Dougl. ex. Laws) and mixed-conifer forests of western North America. These extensive montane forests are considered to be adapted to a low/moderate-severity fire regime that maintained stands of relatively old trees. However, there is increasing recognition from landscape-scale assessments that, prior to any significant effects of fire exclusion, fires and forest structure were more variable in these forests. Biota in these forests are also dependent on the resources made available by higher-severity fire. A better understanding of historical fire regimes in the ponderosa pine and mixed-conifer forests of western North America is therefore needed to define reference conditions and help maintain characteristic ecological diversity of these systems. We compiled landscape-scale evidence of historical fire severity patterns in the ponderosa pine and mixed-conifer forests from published literature sources and stand ages available from the Forest Inventory and Analysis program in the USA. The consensus from this evidence is that the traditional reference conditions of low-severity fire regimes are inaccurate for most forests of western North America. Instead, most forests appear to have been characterized by mixed-severity fire that included ecologically significant amounts of weather-driven, high-severity fire. Diverse forests in different stages of succession, with a high proportion in relatively young stages, occurred prior to fire exclusion. Over the past century, successional diversity created by fire decreased. Our findings suggest that ecological management goals that incorporate successional diversity created by fire may support characteristic biodiversity, whereas current attempts to "restore" forests to open, low-severity fire conditions may not align with historical reference conditions in most ponderosa pine and mixed-conifer forests of western North America.
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Payments for watershed services (PWS) programs are becoming a popular governance approach in the western United States (US) to fund forest management aimed at source water protection. In this paper we conduct a cost-benefit analysis (CBA) of one of the first collaboratively funded PWS programs in the US, located in the municipal watersheds servicing Denver, Colorado. We combine wildfire modeling, sediment modeling, and primary and secondary data on economic values to quantify the impact of the program on protecting multiple values at risk. Our results show that while the program has led to diverse societal benefits, it is only economically efficient (benefit-cost ratio greater than one) when all co-benefits beyond source water protection are considered, and fuels treatments are assumed to encounter wildfire. When the probability of wildfire is accounted for, economic benefits would need to be triple what was estimated in our analysis to achieve economic efficiency. Our findings suggest that improving spatial prioritization of interventions would increase economic benefits and better data on treatment placement and costs would help facilitate future CBA of PWS programs focused on wildfire mitigation.
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Even though wildfires constitute a natural phenomenon, they may have severe implications with respect to the socioeconomic structure of the affected population and the ecological wealth of a territory, especially when they burn under high intensities. Timing of the initial attack is thus crucial to fire control in areas that fires are considered to be under high threat of burning. The aim of this paper is to investigate the combined use of simulation modeling and spatial optimization to assess the pre-positioning of fire-management resources on a small Greek island, Thasos, based on the current and desired fire agency capabilities, maximization of environmental protection, and rationalization of financial resources. The estimation of burn probability (BP) depicted specific areas of high fire hazard in the southern, central, and western part of the island, where essential preventive measures should be undertaken. Based on this result, BP was then used as a primary input for the assessment of optimal locations of fire operation agencies in order to achieve the maximal coverage under certain (already available) and minimum number of fire-fighting vehicles in different time windows. The results generated three differentiated optimal location schemes [8 available vehicles within either 10 (immediate response time) or 31 min (average response time) with the current fire resources; 19 and 2 required vehicles within 10 and 31 min, respectively, based on a minimum number of fire resources]. This type of information enables us to propose a relocation of the current fire agency in a southern town of the island. The flexibility and interaction of the models provide a framework for appropriate decision making under a set of political and financial constraints.
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A conceptual framework is presented for identifying preferred feasible and sustainable management actions for a coupled human and natural system. The framework involves: (1) determining operationally and financially feasible management actions; (2) selecting and estimating management objectives for those actions; (3) using the weak or strong sustainability criterion to identify feasible management actions that are sustainable; (4) assigning weights to management objectives; and (5) ranking feasible and sustainable management actions. Management actions, objectives, and weights are selected by the manager. Management actions are ranked using a multiple objective evaluation method and utility values estimated with the utility function U($${\sum}_{i=1}^n{w}_i{V}_{ij}$$), where i designates management objective, j designates management action, wi is the weight assigned to the ith management objective, Vij is the estimated value of the ith management objective for the jth management action, and $${\sum}_{i=1}^n{w}_i\,{=}\,1$$. Management objectives are simulated or estimated using biophysical and economic data and models. An empirical application of the framework is presented that uses the Stochastic Efficiency with Respect to a Function method and utility values to rank three preselected fuel treatment strategies and determines preferred treatment strategies for U.S. Forest Service land in Flathead County, Montana for two risk attitudes (i.e., almost risk neutral and strongly risk averse).
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Among the concerns raised by climatic change is the potential for the additional release of carbon dioxide as a result of biomass combustion. Most of the carbon emissions from wildfires are from the combustion of litter, duff, and small woody debris, whereas most, if not all, of the biomass stored in the boles of large trees is not combusted. Consequently, most of the carbon stored in forests remains unconsumed, even by high-severity wildfires. Thus the application of fuel reduction treatments, while sometimes effective in reducing fire severity and carbon emissions, nearly always result in a net reduction in carbon storage. Postfire carbon emissions from the decomposition of fire-killed biomass can continue for decades, but effects of forest regrowth can exceed the losses of carbon from biomass combustion and the decomposition of fire-killed biomass within 5-50 years, depending on the ecosystem. © 2015 by Dominick A. DellaSala and Chad T. Hanson. Published by Elsevier Inc. All rights reserved.
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We compiled existing data and information to characterize the condition and trends in high priority natural resources in Crater Lake National Park. This report, and the spatial datasets provided with it, is intended to inform and support park managers and scientists in developing recommendations for improving or maintaining natural resource conditions in the park. It also can assist park resource managers in meeting the reporting requirements of the Government Performance Results Act and Office of Management and Budget. In attempts to describe the current condition and trends of the park’s natural resources, we followed generally the Environmental Protection Agency’s “Framework for Assessing and Reporting on Ecological Condition” (Young and Sanzone 2002). Specifically, we first identified seven natural resource themes considered by this park’s managers and scientists to be most important. They are:  Precipitation, Temperature, Snowpack, and Lake Levels  Surface Water Quality  Aquatic Life  Terrestrial Vegetation  Wildlife  Air Quality  Natural Quality of the Park Experience We identified 24 indicators to evaluate these seven resource concerns. For each indicator we then attempted to define reference conditions to which we could compare present conditions. Making that comparison, we described the condition of each indicator as “Good,” “Somewhat Concerning,” “Significant Concern,” or “Indeterminate.” We described each indicator’s trend as “Improving,” “Somewhat Concerning,” “Significant Concern,” or “Indeterminate.” In each instance where we applied these terms, we also described (as high, moderate, or low) the certainty associated with our estimate. Where reference conditions that were the basis for our comparisons lacked quantitative standards, we based the assessment on qualitative descriptions of least-altered resource conditions derived from historical accounts, scientific literature, and professional opinion. Applying the 24 indicators, we determined that the condition of three indicators is of Significant Concern in this park. Those are: the distribution of forest stand ages, fire rotations, and extent of invasive pathogens. The reduced frequency of fire in some parts of the park has created conditions that are at the extreme end of the natural age distribution for the park’s forest types. This can restrict the park’s capacity to effectively support the region’s wildlife and plant diversity. We assigned a rating of “Somewhat Concerning” to seven indicators:  Changes in Productivity and Diversity in Non-caldera Water Bodies  Changes in Ecologically Harmful Aquatic Species xiv  Recovery of Disturbed Areas  Diversity of Native Terrestrial Wildlife Species; Rare Species  Connectivity and Extent of Important Terrestrial Habitats  Deposition of Airborne Contaminants  Ozone Levels Park managers have limited capacity to influence the condition of the last three indicators. However, NPS has had some success working with policy makers and regulators to enforce stricter standards when park data indicated air quality problems resulting from local sources. The condition of a plurality of the indicators (11), including the condition of the caldera lake itself, was rated “Good.” However, information was insufficient to rate the present condition or trends of four important indicators throughout all areas of the park:  Annual Depth, Volume, and Persistence of Snowpack  Water Quality in Non-caldera Water Bodies  Rare Plants and Native Plant Diversity  Dark Night Sky Information sufficient to estimate trends was lacking for 16 of the 24 indicators, and none of the trends calculations were considered to have a high degree of certainty.
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Trees in U.S. cities, the wildland-urban interface and rural areas are responding to climate change. Longer growing seasons help trees grow faster in many areas, but simultaneously result in longer periods of water stress. Western forests are particularly vulnerable to increasing wildfire and insect outbreaks. In rural areas especially, the demand for wood products, watersheds for clean water, and recreation opportunities interact with emerging bioenergy markets, potential for carbon credits, and changing private forest ownerships. These factors along with climate-induced risks to forests and the perceptions of public land management make the future use of forests a challenging public issue.
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Key Messages 1. Climate change is increasing the vulnerability of many forests to ecosystem changes and tree mortality through fire, insect infestations, drought, and disease outbreaks. 2. U.S. forests and associated wood products currently absorb and store the equivalent of about 16% of all carbon dioxide (CO2) emitted by fossil fuel burning in the U.S. each year. Climate change, combined with current societal trends in land use and forest management, is projected to reduce this rate of forest CO2 uptake. 3. Bioenergy could emerge as a new market for wood and could aid in the restoration of forests killed by drought, insects, and fire. 4. Forest management responses to climate change will be influenced by the changing nature of private forestland ownership, globalization of forestry markets, emerging markets for bioenergy, and U.S. climate change policy.
Technical Report
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Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical setting, fuels, and weather combine to determine wildfire intensity (the rate at which it consumes fuel) and severity (the effect fire has on vegetation, soils, buildings, watersheds, and so forth). As a result of fire exclusion, timber harvesting, and livestock grazing, millions of acres of forestlands (mainly in dry forests dominated by ponderosa pine and/or Douglas-fir) contain a high accumulation of flammable fuels compared to conditions prior to the 20th century. Forests with high stem density and fuel loading combined with extreme fire weather conditions have led to severe and large wildfires (such as those seen in the summers of 2000 and 2002 and the fall of 2003) that have put a number of important values at risk. Although homes in the path of a wildfire are perhaps the most immediately recognized value, these wildfires also put numerous other human and ecological values at risk, such as power grids, drinking water supplies, firefighter safety, critical habitat, soil productivity, and air quality. For a given set of weather conditions, fire behavior is strongly influenced by stand and fuel structure. Crown fires in the dry forest types represent an increasing challenge for fire management as well as a general threat to the ecology of these forests and the closely associated human values. Crown fires are dependent on the sequence of available fuels starting from the ground surface to the canopy. Limiting crown fire in these forests can, thus, be accomplished by fuel management actions that first reduce surface and ladder fuels before manipulating canopy fuels. Reducing crown fire and wildland fire growth across landscapes decreases the chances of developing large wildfires that affect human values adjacent to forested areas. However, a narrow focus on minimizing crown fire potential will not necessarily reduce the damage to homes and ecosystems when fires do occur there. Homes are often ignited by embers flying far from the fire front, and by surface fires. Fire effects on ecosystems can also occur during surface fires where fine fuels and deep organic layers are sufficient to generate high temperatures for long periods. Fuel treatments can help produce forest structures and fuel characteristics that then reduce the likelihood that wildfires will cause large, rapid changes in biophysical conditions. Fuel treatments can also help modify fire behavior sufficiently so that some wildfires can be suppressed more easily. Subsequent, sustained fuel treatments can maintain these conditions. Different fuel reduction methods target different components of the fuel bed. Thinning mainly affects standing vegetation, and other types of fuel treatments such as prescribed fire and pile burning woody fuels are needed to modify the combustion environment of surface fuels. In forests that have not experienced fire for many decades, multiple fuel treatments-that is, thinning and surface fuel reduction-may be required to significantly affect crown fire and surface fire hazard. Fuel treatments cannot guarantee benign fire behavior but can reduce the probability that extreme fire behavior will occur. Fuel treatments can be designed to restore forest conditions to a more resilient and resistant condition than now exists in many forests, and subsequent management could maintain these conditions, particularly in dry forests (ponderosa pine and Douglas-fir) where crown fires were infrequent. The degree of risk reduction will depend to some degree on the level of investment, social and economic acceptability of treatments, and concurrent consideration of other resource values (for example, wildlife). This report describes the kinds, quality, amount, and gaps of scientific knowledge for making informed decisions on fuel treatments used to modify wildfire behavior and effects in dry forests of the interior Western United States (especially forests dominated by ponderosa pine and Douglas-fir). A review of scientific principles and applications relevant to fuel treatment primarily for the dry forests is provided for the following topics: fuels, fire hazard, fire behavior, fire effects, forest structure, treatment effects and longevity, landscape fuel patterns, and scientific tools useful for management and planning.
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It is impractical to address the long-term effect of forest man- agement strategies on erosion, sedimentation, and the resultant damage to fish habitat experimentally because to do so would require studying large watersheds for a century or more. Monte Carlo simulations were conducted on three hypothetical 10 000 ha, fifth-order forested watersheds. One wa- tershed was left undisturbed, one was completely clearcut and roaded in a decade, and one was cut at the rate of 1% each year. Each cutting strategy was repeated in succeeding centuries.
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Synthesis of the literature suggests that physical, chemical, and biological elements of a watershed interact with long-term climate to influence fire regime, and that these factors, in concordance with the postfire vegetation mosaic, combine with local-scale weather to govern the trajectory and magnitude of change following a fire event. Perturbation associated with hydrological processes is probably the primary factor influencing postfire persistence of fishes, benthic macroin­ vertebrates, and diatoms in fluvial systems. It is apparent that salmonids have evolved strategies to survive perturbations occurring at the frequency of wildland fires (100-102 years), but local populations of a species may be more ephemeral. Habitat alteration probably has the greatest impact on individual organisms and local populations that are the least mobile, and reinvasion will be most rapid by aquatic organisms with high mobility. It is becoming increasingly apparent that during the past century fire suppression has altered fire regimes in some vegetation types, and consequently, the probability of large stand-replacing fires has increased in those areas. Current evidence suggests, however, that even in the case of extensive high-severity fires, local extirpation of fishes is patchy, and recolonization is rapid. Lasting detrimental effects on fish populations have been limited to areas where native populations have declined and become increasingly isolated because of anthropogenic activities. A strategy of protecting robust aquatic communities and restoring aquatic habitat structure and life history complexity in degraded areas may be the most effective means for insuring the persistence of native biota where the probability of large-scale fires has increased.
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Recent changes in the forest policies, regulations, and laws affecting public lands encourage postfire salvage logging, an activity that all too often delays or prevents recovery. In contrast, the 10 recommendations proposed here can improve the condition of watersheds and aquatic ecosystems. Keywords: aquatic ecosystems, postfire salvage logging, public land management, salmonids, western forests
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Erosion on roads is an important source of fine-grained sediment in streams draining logged basins of the Pacific Northwest. Runoff rates and sediment concentrations from 10 road segments subject to a variety of traffic levels were monitored to produce sediment rating curves and unit hydrographs for different use levels and types of surfaces. These relationships are combined with a continuous rainfall record to calculate mean annual sediment yields from road segments of each use level. A heavily used road segment in the field area contributes 130 times as much sediment as an abandoned road. A paved road segment, along which cut slopes and ditches are the only sources of sediment, yields less than 1% as much sediment as a heavily used road with a gravel surface.
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Patterns of native and alien plant diversity in response to disturbance were examined along an elevational gradient in blue oak savanna, chaparral, and coniferous forests. Total species richness, alien species richness, and alien cover declined with ele-vation, at scales from 1 to 1000 m 2 . We found no support for the hypothesis that community diversity inhibits alien invasion. At the 1-m 2 point scale, where we would expect competitive interactions between the largely herbaceous flora to be most intense, alien species richness as well as alien cover increased with increasing native species richness in all communities. This suggests that aliens are limited not by the number of native competitors, but by resources that affect establishment of both natives and aliens. Blue oak savannas were heavily dominated by alien species and consistently had more alien than native species at the 1-m 2 scale. All of these aliens are annuals, and it is widely thought that they have displaced native bunchgrasses. If true, this means that aliens have greatly increased species richness. Alternatively, there is a rich regional flora of native annual forbs that could have dominated these grasslands prior to displacement by alien grasses. On our sites, livestock grazing increased the number of alien species and alien cover only slightly over that of sites free of livestock grazing for more than a century, indicating some level of permanency to this invasion. In chaparral, both diversity and aliens increased markedly several years after fire. In-vasive species are rare in undisturbed shrublands, and alien propagules fail to survive the natural crown fires in these ecosystems. Thus, aliens necessarily must colonize after fire and, as a consequence, time since fire is an important determinant of invasive presence. Blue oak savannas are an important propagule source for alien species because they maintain permanent populations of all alien species encountered in postfire chaparral, and because the vegetation mosaic in this region places them in proximity to chaparral. The speed at which alien propagules reach a burned site and the speed at which the shrublands return to their former closed-canopy condition determine alien invasion. Frequent burning of this vegetation alters the balance in favor of alien invasion. In the higher-elevation coniferous forests, species diversity was a function of fire severity and time since fire. High-intensity fires create gaps that decrease canopy coverage and increase light levels and nutrients for an ephemeral successional flora. Few species have persistent seed banks, so the time since fire is an important determinant of colonization success. There was a highly significant interaction between fire severity and time since fire for understory cover, species richness, and alien richness and cover. Understory was sparse in the first year after fire, particularly in low-severity burns, and increased substantially several years after fire, particularly on high-severity burns. Both fire severity and time since fire affected alien species richness and dominance. Coniferous forests had about one-third as many alien species as the foothill oak savannas, and fewer than half of the species were shared between these communities. Unburned coniferous forests were largely free of alien species, whereas some burned sites had a significant alien presence, which presents a challenge for fire restoration of these forests.
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The basic premise behind many projects aimed at wildfire hazard reduction and ecological restoration in forests of the western United States is the idea that unnatural fuel buildup has resulted from suppression of formerly frequent fires. This premise and its implications need to be critically evaluated by conducting area-specific research in the forest ecosystems targeted for fuels or ecological restoration projects. Fire regime researchers need to acknowledge the limitations of fire history methodology and avoid over-reliance on summary fire statistics such as mean fire interval and rotation period. While fire regime research is vitally important for informing decision making in the areas of wildfire hazard mitigation and ecological restoration, there is much need for improving the way researchers communicate their results to managers and the way managers use this information.
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The purpose of this paper is to promote a broad and flexible perspective on ecological restoration of Southwestern (U.S.) ponderosa pine forests. Ponderosa pine forests in the region have been radically altered by Euro-American land uses, including livestock grazing, fire suppression, and logging. Dense thickets of young trees now abound, oldgrowth and biodiversity have declined, and human and ecological communities are increasingly vulnerable to destructive crown fires. A consensus has emerged that it is urgent to restore more natural conditions to these forests. Efforts to restore Southwestern forests will require extensive projects employing varying combinations of young-tree thinning and reintroduction of low-intensity fires. Treatments must be flexible enough to recognize and accommodate: high levels of natural heterogeneity; dynamic ecosystems; wildlife and other biodiversity considerations; scientific uncertainty; and the challenges of on-the-ground implementation. Ecological restoration should reset ecosystem trends toward an envelope of ‘‘natural variability,’’ including the reestablishment of natural processes. Reconstructed historic reference conditions are best used as general guides rather than rigid restoration prescriptions. In the long term, the best way to align forest conditions to track ongoing climate changes is to restore fire, which naturally correlates with current climate. Some stands need substantial structural manipulation (thinning) before fire can safely be reintroduced. In other areas, such as large wilderness and roadless areas, fire alone may suffice as the main tool of ecological restoration, recreating the natural interaction of structure and process. Impatience, overreaction to crown fire risks, extractive economics, or hubris could lead to widespread application of highly intrusive treatments that may further damage forest ecosystems. Investments in research and monitoring of restoration treatments are essential to refine restoration methods. We support the development and implementation of a diverse range of scientifically viable restoration approaches in these forests, suggest principles for ecologically sound restoration that immediately reduce crown fire risk and incrementally return natural variability and resilience to Southwestern forests, and present ecological perspectives on several forest restoration approaches.
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Natural disturbances are an important source of environmental heterogeneity that have been linked to species diversity in ecosystems. However, spatial and temporal patterns of disturbances are often evaluated separately. Consequently, rates and scales of existing disturbance processes and their effects on biodiversity are often uncertain. We have studied both spatial and temporal patterns of contemporary fires in the Sierra Nevada Mountains, California, USA. Patterns of fire severity were analyzed for conifer forests in the three largest fires since 1999. These fires account for most cumulative area that has burned in recent years. They burned relatively remote areas where there was little timber management. To better characterize high-severity fire, we analyzed its effect on the survival of pines. We evaluated temporal patterns of fire since 1950 in the larger landscapes in which the three fires occurred. Finally, we evaluated the utility of a metric for the effects of fire suppression. Known as Condition Class it is now being used throughout the United States to predict where fire will be uncharacteristically severe. Contrary to the assumptions of fire management, we found that high-severity fire was uncommon. Moreover, pines were remarkably tolerant of it. The wildfires helped to restore landscape structure and heterogeneity, as well as producing fire effects associated with natural diversity. However, even with large recent fires, rates of burning are relatively low due to modern fire management. Condition Class was not able to predict patterns of high-severity fire. Our findings underscore the need to conduct more comprehensive assessments of existing disturbance regimes and to determine whether natural disturbances are occurring at rates and scales compatible with the maintenance of biodiversity.
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Successful fire exclusion in the 20th century has created severe fire problems across the West. Not every forest is at risk of uncharacteristically severe wildfire, but drier forests are in need of active management to mitigate fire hazard. We summarize a set of simple principles important to address in fuel reduction treatments: reduction of surface fuels, increasing the height to live crown, decreasing crown density, and retaining large trees of fire-resistant species. Thinning and prescribed fire can be useful tools to achieve these objectives. Low thinning will be more effective than crown or selection thinning, and management of surface fuels will increase the likelihood that the stand will survive a wildfire. Five empirical examples of such treatment are discussed: Hayfork fires, California, 1987; Tyee fire, Washington, 1994; Megram fire, California, 1999; Hayman fire, Colorado, 2002; and the Cone fire, California, 2002. Applying treatments at an appropriate landscape scale will be critical to the success of fuel reduction treatments in reducing wildfire losses in Western forests.
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Fire is an important part of the disturbance regimes of northwestern US forests and its role in maintaining and altering forest vegetation is evident in the paleoecological record of the region. Long-term reconstructions of Holocene fire regimes, provided by the analysis of charcoal, pollen, and other fire proxies in a network of lake records, indicate that the Pacific Northwest and summer-dry regions of the northern Rocky Mountains experienced their highest fire activity in the early Holocene (11,000–7000 years ago) and during the Medieval Warm Period (ca. 1000 years ago) when drought conditions were more severe than today. In contrast, in summer-wet areas of the northern Rocky Mountains, the period of highest fire activity was registered in the last 7000 years when dry woodland vegetation developed. When synthesized across the entire northwestern US, the paleoecological record reveals that past and present fire regimes are strongly controlled by climate changes occurring on multiple time scales. The scarcity of fires in the 20th century in some northwestern US ecosystems may be the result of successful fire suppression policies, but in wetter forests this absence is consistent with long-term fire regime patterns. In addition, simulations of potential future climate and vegetation indicate that future fire conditions in some parts of the northwestern US could be more severe than they are today. The Holocene record of periods of intensified summer drought is used to assess the nature of future fire–climate–vegetation linkages in the region.
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The management of fire-prone forests is one of the most controversial natural resource issues in the US today, particularly in the west of the country. Although vegetation and wildlife in these forests are adapted to fire, the historical range of fire frequency and severity was huge. When fire regimes are altered by human activity, major effects on biodiversity and ecosystem function are unavoidable. We review the ecological science relevant to developing and implementing fire and fuel management policies for forests before, during, and after wildfires. Fire exclusion led to major deviations from historical variability in many dry, low-elevation forests, but not in other forests, such as those characterized by high severity fires recurring at intervals longer than the period of active fire exclusion. Restoration and management of fire-prone forests should be precautionary, allow or mimic natural fire regimes as much as possible, and generally avoid intensive practices such as post-fire logging and planting. yes
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Understanding the relative influence of fuels and climate on wildfires across the Rocky Mountains is necessary to predict how fires may respond to a changing climate and to define effective fuel management approaches to controlling wildfire in this increasingly populated region. The idea that decades of fire suppression have promoted unnatural fuel accumulation and subsequent unprecedentedly large, severe wildfires across western forests has been developed primarily from studies of dry ponderosa pine forests. However, this model is being applied uncritically across Rocky Mountain forests (e.g., in the Healthy Forests Restoration Act). We synthesize current research and summarize lessons learned from recent large wildfires (the Yellowstone, Rodeo-Chediski, and Hayman fires), which represent case studies of the potential effectiveness of fuel reduction across a range of major forest types. A “one size fits all” approach to reducing wildfire hazards in the Rocky Mountain region is unlikely to be effective and may produce collateral damage in some places.
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Western United States forest wildfire activity is widely thought to have increased in recent decades, yet neither the extent of recent changes nor the degree to which climate may be driving regional changes in wildfire has been systematically documented. Much of the public and scientific discussion of changes in western United States wildfire has focused instead on the effects of 19th- and 20th-century land-use history. We compiled a comprehensive database of large wildfires in western United States forests since 1970 and compared it with hydroclimatic and land-surface data. Here, we show that large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests, where land-use histories have relatively little effect on fire risks and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt.
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Fire exclusion policies have affected stand structure and wildfire hazard in north American ponderosa pine forests. Wildfires are becoming more severe in stands where trees are densely stocked with shade-tolerant understory trees. Although forest managers have been employing fuel treatment techniques to reduce wildfire hazard for decades, little scientific evidence documents the success of treatments in reducing fire severity. Our research quantitatively examined fire effects in treated and untreated stands in western United States national forests. Four ponderosa pine sites in Montana, Washington, California and Arizona were selected for study. Fuel treatments studied include: prescribed fire only, whole-tree thinning, and thinning followed by prescribed fire. On-the-ground fire effects were measured in adjacent treated and untreated forests. We developed post facto fire severity and stand structure measurement techniques to complete field data collection. We found that crown fire severity was mitigated in stands that had some type of fuel treatment compared to stands without any treatment. At all four of the sites, the fire severity and crown scorch were significantly lower at the treated sites. Results from this research indicate that fuel treatments, which remove small diameter trees, may be beneficial for reducing crown fire hazard in ponderosa pine sites.
Article
Present understanding of fire ecology in forests subject to surface fires is based on fire-scar evidence. We present theory and empirical results that suggest that fire-history data have uncertainties and biases when used to estimate the population mean fire interval (FI) or other parameters of the fire regime. First, the population mean FI is difficult to estimate precisely because of unrecorded fires and can only be shown to lie in a broad range. Second, the interval between tree origin and first fire scar estimates a real fire-free interval that warrants inclusion in mean-FI calculations. Finally, inadequate sampling and targeting of multiple-scarred trees and high scar densities bias mean FIs toward shorter intervals. In ponderosa pine (Pinus ponderosa Dougl. ex P. & C. Laws.) forests of the western United States, these uncertainties and biases suggest that reported mean FIs of 2-25 years significantly underestimate population mean FIs, which instead may be between 22 and 308 years. We suggest that uncertainty be explicitly stated in fire-history results by bracketing the range of possible population mean FIs. Research and improved methods may narrow the range, but there is no statistical or other method that can eliminate all uncertainty. Longer mean FIs in ponderosa pine forests suggest that (i) surface fire is still important, but less so in maintaining forest structure, and (ii) some dense patches of trees may have occurred in the pre-Euro-American landscape. Creation of low-density forest structure across all parts of ponderosa pine landscapes, particularly in valuable parks and reserves, is not supported by these results.
Article
Fire exclusion policies have affected stand structure and wildfire hazard in north American ponderosa pine forests. Wildfires are becoming more severe in stands where trees are densely stocked with shade-tolerant understory trees. Although forest managers have been employing fuel treatment techniques to reduce wildfire hazard for decades, little scientific evidence documents the success of treatments in reducing fire severity. Our research quantitatively examined fire effects in treated and untreated stands in western United States national forests. Four ponderosa pine sites in Montana, Washington, California and Arizona were selected for study. Fuel treatments studied include: prescribed fire only, whole-tree thinning, and thinning followed by prescribed fire. On- the-ground fire effects were measured in adjacent treated and untreated forests. We developed post facto fire severity and stand structure measurement techniques to complete field data collection. We found that crown fire severity was mitigated in stands that had some type of fuel treatment compared to stands without any treatment. At all four of the sites, the fire severity and crown scorch were significantly lower at the treated sites. Results from this research indicate that fuel treatments, which remove small diameter trees, may be beneficial for reducing crown fire hazard in ponderosa pine sites. Additional keywords: Pinus ponderosa; Montana; Washington; California; Arizona; fuel treatment; crown fire. W F0 104 5 J. P ollet and P. N. Om i Th inn ing , presc ri bed bu rning an d crow n f i re sev erity in p on deros a pine for e st s
Article
choennagel and colleagues (2004)provide an important contributiontoward explaining how different fireregimes operate in western forests andthe implications for forest manage-ment. We agree that this variabilityneeds to be recognized in forest restora-tion efforts in the West,where a modelof frequent surface fire is often broadlyapplied to areas with different naturalfire egimes.However, we do not agree that thefire severity data from the 2002 Rodeo-Chediski fire in Arizona cited by Schoen-nagel and colleagues indicate that forestmanipulations reduced fire severity.There is no analysis of variance in burnseverity by treatment or setting in thedata cited (Wilmes et al.2002,displayedin figures 7 and 8 in Schoennagel et al.2004). It is not clear that the samplingwas consistent with statistical require-ments for hypothesis testing.Topogra-phy,weather,fire suppression activities,and other factors can strongly influencefire severity,yet Wilmes and colleagues(2002) do not explain how these factorsvary among sites or were controlled forin sampling.Burn severity is typically highly vari-able,and the relative differences in burnseverity by treatment are relatively smallin the data of Wilmes and colleagues(2002). If burn severity had been sam-pled consistent with statistical consid-erations,it is possible that the data mightindicate there was no treatment effect.Without adequate sampling design andstatistical analysis, it is impossible toreasonably determine what effect treat-ments had on fire severity in the Rodeo-Chediski fire.Although evaluating forest manipu-lations aimed at reducing fire severity ina broad ecological context is outside thescope of the article by Schoennagel andcolleagues (2004), that work needs tobe done. Mechanized fuel treatmentscause collateral damage to ecosystemcomponents, including soils, aquatics,and vegetation; they also have the po-tential to spread exotic plants andpathogens.The negative ecological im-pacts ofsalvage loggingNone treatmentdescribed in Wilmes and colleagues(2002)Nhave been identified in con-siderable detail (Beschta et al.2004,Lin-denmayer et al. 2004). Even if suchtreatments do reduce fire severity, theecological cost of those treatments mayoutweigh any positive effects. In mostcases,the negative effects of treatmentswill cover a substantially greater areathan that for which fire severity might bereducedNif, that is, fire should occur.The likelihood that treatments will affectwildfire severity is relatively low,becauseofthe low probability offire at a specificlocation and the transient nature ofsuchtreatments.In conclusion,we do not dispute thatfire regimes have been altered in south-western forests, nor do we necessarilydispute that forest manipulations canreduce fire severity in these systems.However,there remain major questionsregarding the likely effectiveness and thenet ecological effects ofsuch manipula-tions;these should be answered by rig-orous research before large areas offorestare reconfigured.This will require bet-ter understanding of the natural rolethat fires and fuels play in differentforests.We commend Schoennagel andcolleagues for adding to our under-standing on this front.JONATHAN J.RHODES Conservation HydrologistPlaneto Azul Hydrologic ConsultantsPO Box 15286Portland,OR 97293 DENNIS C.ODIONInstitute for Computational EarthSystems ScienceUniversity of CaliforniaSanta Barbara,CA 93106
Article
Patterns of disconnected fuel treatment patches that overlap in the heading fire spread direction are theoretically effective in changing forward fire spread rate. The analysis presented here sought to find the unit shape and pattern for a given level of treatment that has the maximum effect on forward spread rate. This occurs when the treatment units cause the fire to spread through them at the same rate as it spreads around them. Simulations suggested that these treatment patterns reduce the spread rate or fireline intensity over much of the area burned, even outside the treatment units where the fire was forced to flank. The ideal patterns are theoretically scale independent, allowing for flexible application across heterogeneous landscapes. The topology of these patterns has implications for designing landscape-level fuel treatment patterns and for understanding spatial dynamics of fuel patterns across landscapes. FOR. SCI. 47(2):219–228.
Article
1. Invasion by alien plant species represents a challenge to land managers throughout the world as they attempt to restore frequent fire-adapted ecosystems following decades of fire exclusion. In ponderosa pine Pinus ponderosa forests of western North America, the response of alien species to restoration treatments has not been well documented, particularly for alien species capable of altering environmental conditions (trans -formers). Understanding alien species dynamics is critical for developing treatments that accomplish restoration goals while minimizing alien invasion. 2. We used a replicated, randomized block experiment to compare the effects of an untreated control and thin-only, burn-only and thin-burn treatments on alien and transformer understorey species at multiple spatial scales (1 m 2 , 100 m 2 and 1000 m 2). Data were collected pre-treatment and for multiple post-treatment years. We compared richness and cover of alien species and transformer species among treatments, and identified environmental variables correlated with transformer species cover. Indicator species analysis was used to identify transformer species associated with specific treatments. 3. Alien and transformer species richness and cover were significantly higher in the thin-burn than in all other treatments at all spatial scales. Thin-only and burn-only treatments showed greater alien and transformer species responses than the control at the larger 100-m 2 and 1000-m 2 scales. 4. Increased transformer cover was strongly correlated with increased tree crown scorch height and removal of overstorey trees. 5. The thin-burn treatment had four transformer species as indicators, the thin-only had one, while the burn-only and control had none. 6. Synthesis and applications . The results show that alien species, including trans -formers, respond to restoration treatments, especially the combined thin-burn treatment. Therefore monitoring for alien species invasion is an essential component of a restoration programme. Abundance of transformer species increased with increasing disturbance intensity, suggesting that less intense single-disturbance treatments (burn-only, thin-only) or incremental treatments may be preferred in some applications. Where more intense treatments are required to meet management objectives, specific strategies, such as seeding of native species, limiting grazing before and after treatment and harvesting over a protective winter snowpack, may be necessary to limit alien invasion.
Article
Large wild fires occurring in forests, grasslands, and chaparral in the last few years have aroused much public concern. Many have described these events as “catastrophes” that must be prevented through aggressive increases in forest thinning. Yet the real catastrophes are not the fires themselves but those land uses, in concert with fire-suppression policies that have resulted in dramatic alterations to ecosystem structure and composition. The first step in the restoration of biological diversity (forest health) of western landscapes must be to implement changes in those factors that have caused degradation or are preventing recovery. This includes changes in policies and practices that have resulted in the current state of wildland ecosystems. Restoration entails much more than simple structural modifications achieved though mechanical means. Restoration should be undertaken at landscape scales and must allow for the occurrence of dominant ecosystem processes, such as the natural fire regimes achieved through natural and/or prescribed fires at appropriate temporal and spatial scales.
Article
Conservation of native fishes and changing patterns in wildfire and fuels are defining challenges for managers of forested landscapes in the western United States. Many species and populations of native fishes have declined in recorded history and some now occur as isolated remnants of what once were larger more complex systems. Land management activities have been viewed as one cause of this problem. Fires also can have substantial effects on streams and riparian systems and may threaten the persistence of some populations of fish, particularly those that are small and isolated. Despite that, major new efforts to actively manage fires and fuels in forests throughout the region may be perceived as a threat rather than a benefit to conservation of native fishes and their habitats. The management of terrestrial and aquatic resources has often been contentious, divided among a variety of agencies with different goals and mandates. Management of forests, for example, has generally been viewed as an impact on aquatic systems. Implementation of the management-regulatory process has reinforced a uniform approach to mitigate the threats to aquatic species and habitats that may be influenced by management activities. The problems and opportunities, however, are not the same across the landscapes of interest. Attempts to streamline the regulatory process often search for generalized solutions that may oversimplify the complexity of natural systems. Significant questions regarding the influence of fire on aquatic ecosystems, changing fire regimes, and the effects of fire-related management remain unresolved and contribute to the uncertainty. We argue that management of forests and fishes can be viewed as part of the same problem, that of conservation and restoration of the natural processes that create diverse and productive ecosystems. We suggest that progress toward more integrated management of forests and native fishes will require at least three steps: (1) better integration and development of a common conceptual foundation and ecological goals; (2) attention to landscape and ecological context; and (3) recognition of uncertainty.
Article
Quantitative fire risk analysis depends on characterizing and combining fire behavior probabilities and effects. Fire behavior probabilities are different from fire occurrence statistics (historic numbers or probabilities of discovered ignitions) because they depend on spatial and temporal factors controlling fire growth. That is, the likelihood of fire burning a specific area is dependent on ignitions occurring off-site and the fuels, topography, weather, and relative fire direction allowing each fire to reach that location. Research is required to compare computational short-cuts that have been proposed for approximating these fire behavior distributions. Fire effects in a risk analysis must also be evaluated on a common scale for the variety of values susceptible to wildland fire. This means that appraisals of fire impacts to human infrastructure and ecological values must be measured by the same currency so that the risk assessment yields a single expectation of fire effects. Ultimately, this will help guide planning and investment into management activities that can alter either the probabilities of damaging fire or the susceptibility to those fire behaviors.
Article
Wildfire poses risks to fish and wildlife habitat, among other things. Management projects to reduce the severity of wildfire effects by implementing hazardous fuel reduction treatments also pose risks. How can land managers determine which risk is greater? Comparison of risks and benefits from fuel treatment projects to risks from severe wildfire effects is consistent with policies requiring public land managers to analyze short- and long-term environmental effects. However, formulating the problem as a comparison of temporal considerations often results in decisions to reject fuels treatment projects near imperiled species habitat, even though the adverse effects of short-term project actions may result in substantial long-term net benefits from reducing the severity of wildfire effects. Consistent with widely accepted ecological risk assessment methods, the problem is formulated in a conceptual model. Salmonid fish populations are the risk assessment endpoint, and one stressor adversely affecting them is sediment from wildfire or logging. The model compares short-term effects of implementing fuels reduction treatments to longer-term wildfire effects with and without fuel treatments, including risk reduction benefits. Used quantitatively or qualitatively, the model may contribute to sustainable resource management decisions by improving communication among stakeholders, risk managers in land and resource management agencies, and risk assessors in agencies responsible for enforcing the Endangered Species Act.
Article
Forest-fire policy of U.S. federal agencies has evolved from the use of small patrols in newly created National Parks to diverse policy initiatives and institutional arrangements that affect millions of hectares of forests. Even with large expenditures and substantial infrastructure dedicated to fire suppression, the annual area burned by wildfire has increased over the last decade. Given the current and future challenges of fire management, and based on analytical research and review of existing policies and their implications, we believe several changes and re-emphases in existing policy are warranted. Most importantly, the actual goal of fuels-management projects should be the reduction of potential fire behavior and effects, not the simple reduction of fuels. To improve safety and economic efficiency, fire-suppression policies should recognize differences in the characteristics of wildfires, and strategies should be tailored to better respond to the unique demands of each fire. Where forest fires are burning large areas, as in the western United States, reducing the trend of increased amounts of burned area may require a diversity of treatments, including prescribed burning, mechanical fuels treatment, and increased use of the Wildland Fire Use Policy. Assessment of how fire is affecting forests would be enhanced if land-management agencies reported the area burned by low-, mixed-, and high-severity fire and what proportion is outside the desired trend or range of conditions for each forest type. Congress should provide an improved budgetary process for fire and fuels management, with a larger annual federal fire-suppression budget. Additionally, reducing annual area burned will require long-term coordinated efforts by federal and state governments, with robust partnerships between land-management agencies and the public in collaborative planning and stewardship. Research and adaptive management are essential in allowing fire-hazard-reduction projects to move forward where proposed projects are met with uncertainty and mistrust. While legislative reform may be desirable, a strategy that is not entirely dependent on new legislation is needed. Building on existing programs that are consistent with a science-based strategy will enable land-management agencies to better utilize information in pursuit of the overall objective of reducing uncharacteristically severe wildfires. yes
Article
Performance of fuel treatments in modifying behavior and effects of the largest wildfires has rarely been evaluated, because the necessary data on fire movement, treatment characteristics, and fire severity were not obtainable together. Here we analyzed satellite imagery and prescribed fire records from two Arizona wildfires that occurred in 2002, finding that prescribed fire treatments reduced wildfire severity and changed its progress. Prescribed burning in ponderosa pine forests 1-9 years before the Rodeo and Chediski fires reduced fire severity compared with untreated areas, despite the unprecedented 1860-km2 combined wildfire sizes and record drought. Fire severity increased with time since treatment but decreased with unit size and number of repeated prescribed burn treatments. Fire progression captured by Landsat 7 enhanced thematic mapper plus (ETM+) clearly showed the fire circumventing treatment units and protecting areas on their lee side. This evidence is consistent with model predictions that suggest wildland fire size and severity can be mitigated by strategic placement of treatments.
Article
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