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  • Library: Increase in forest fire hazard

    Evergreen Alliance Staff
    Jennifer N. Baron, Paul F. Hessburg, Marc-André Parisien, Gregory A. Greene, Sarah E. Gergel and Lori D. Daniels
    Background A clear understanding of the connectivity, structure, and composition of wildland fuels is essential for effective wildfire management. However, fuel typing and mapping are challenging owing to a broad diversity of fuel conditions and their spatial and temporal heterogeneity. In Canada, fuel types and potential fire behavior are characterized using the Fire Behavior Prediction (FBP) System, which uses an association approach to categorize vegetation into 16 fuel types based on stand structure and composition. In British Columbia (BC), provincial and national FBP System fuel type maps are derived from remotely sensed forest inventory data and are widely used for wildfire operations, fuel management, and scientific research. Despite their widespread usage, the accuracy and applicability of these fuel type maps have not been formally assessed. To address this knowledge gap, we quantified the agreement between on‐site assessments and provincial and national fuel type maps in interior BC.
    Results We consistently found poor correspondence between field assessment data and both provincial and national fuel types. Mismatches were particularly frequent for (i) dry interior ecosystems, (ii) mixedwood and deciduous fuel types, and (iii) post‐harvesting conditions. For 58% of field plots, there was no suitable match to the extant fuel structure and composition. Mismatches were driven by the accuracy and availability of forest inventory data and low applicability of the Canadian FBP System to interior BC fuels.
    Conclusions The fuel typing mismatches we identified can limit scientific research, but also challenge wildfire operations and fuel management decisions. Improving fuel typing accuracy will require a significant effort in fuel inventory data and system upgrades to adequately represent the diversity of extant fuels. To more effectively link conditions to expected fire behavior outcomes, we recommend a fuel classification approach and emphasis on observed fuels and measured fire behavior data for the systems we seek to represent.
    This study was reported in the March 3, 2024 Globe and Mail: Inaccurate data on forest fuels amy stoke wildfires, study finds
    (2024) Fuel types misrepresent forest structure and composition in interior British Columbia: a way forward Jen Baron et al.pdf

    Raven Tree
    ABSTRACT: As fires become more frequent due to climate change, and the footprint of timber harvesting continues, the cumulative effects of multiple disturbances will become more prevalent across the boreal forest. While emerging literature highlights the ecological consequences of these interactions, such as threatening biodiversity, watershed health and regeneration, there remains little information on their geographic scale. The purpose of this study is to quantify the cumulative impacts of fire and harvest disturbance in two study regions (Saskatchewan, Canada, and Angara, Russia), including both their additive and compounding effects. Study regions were chosen based on high rates of disturbance from harvest and fire, relative to their respective countries. While data were available for harvest and fire in Saskatchewan, and for harvest in Angara, fire polygons needed to be digitized by hand for Angara. To do so, I used a MODIS burned area product to guide the search for fires, and derived the difference Normalized Burned Ratio from Landsat imagery to trace fire perimeters. Of the total study areas, 8% of Saskatchewan and 22% of Angara were impacted by fire, harvest or both, while 0.26% and 2.67%, respectively, were impacted by successive disturbances between 2001-2017. Harvesting increased the total area disturbed by 26% and the areas successively disturbed by 73% in Saskatchewan, and by 14% and 30%, respectively, in Angara. The compounding impacts of successive disturbances may be mitigated by re-evaluating priority regions for firefighting or reducing the flammability of regenerating stands. However, landscape level approaches will be necessary to address the additive impacts of harvest and fire, such as setting maximum disturbance thresholds.
    Cumulative patterns of fire and harvest disturbance- Comparing case studies from Russia and Canada (2019).pdf

    Raven Tree
    ABSTRACT: This is the opinion and order (2019) made by a US District Court in Oregon in a case brought against the US Bureau of Land Management by Oregon Wild. In it, analysis of BLM's record of conduct regarding a specific clearcut makes evident that BLM was aware that, following logging, a higher fire hazard would exist for 40 years. Although independent scientists studying the issue have found that logging increases fire risk, this is one of very few examples in which the record of a land manager admitting this relationship has been made public.
    Cascadia Wildlands v. Bureau of Land Management (2019).pdf

    Raven Tree
    By Harold S. J. Zald and Christopher J. Dunn
    ABSTRACT: Many studies have examined how fuels, topography, climate, and fire weather influence fire severity. Less is known about how different forest management practices influence fire severity in multi-owner landscapes, despite costly and controversial suppression of wildfires that do not acknowledge ownership boundaries. In 2013, the Douglas Complex burned over 19,000 ha of Oregon & California Railroad (O&C) lands in Southwestern Oregon, USA. O&C lands are composed of a checkerboard of private industrial and federal forestland (Bureau of Land Management, BLM) with contrasting management objectives, providing a unique experimental landscape to understand how different management practices influence wildfire severity. Leveraging Landsat based estimates of fire severity (Relative differenced Normalized Burn Ratio, RdNBR) and geospatial data on fire progression, weather, topography, pre-fire forest conditions, and land ownership, we asked (1) what is the relative importance of different variables driving fire severity, and (2) is intensive plantation forestry associated with higher fire severity? Using Random Forest ensemble machine learning, we found daily fire weather was the most important predictor of fire severity, followed by stand age and ownership, followed by topographic features. Estimates of pre-fire forest biomass were not an important predictor of fire severity. Adjusting for all other predictor variables in a general least squares model incorporat- ing spatial autocorrelation, mean predicted RdNBR was higher on private industrial forests (RdNBR 521.85 18.67 [mean SE]) vs. BLM forests (398.87 18.23) with a much greater proportion of older forests. Our findings suggest intensive plantation forestry characterized by young forests and spatially homogenized fuels, rather than pre-fire biomass, were significant drivers of wildfire severity. This has implications for perceptions of wildfire risk, shared fire management responsibilities, and developing fire resilience for multiple objectives in multi-owner landscapes.
    Severe fire weather and intensive forest management increase fire severity in a multi-ownership landscape (2018).pdf

    Raven Tree
    By Diane Nicholls and Tom Ethier
    ABSTRACT: This document provides guidance for forest professionals who will plan and implement retention strategies in areas that have experienced extensive natural disturbances. Retention planning refers to the required planning for landscape connectivity, interior forest and intact ecosystem attributes (e.g., overstory trees, vegetation communities, soils and other live and decaying forest structure) that will be retained for habitat, hydrologic function, mid-term timber supply and to support recovery at stand and landscape scales. We provide this guidance now due to the need for retention planning to guide salvage logging in areas affected by the 2017 wildfires.
    Report on 2017 forest fires by BC ministry of Forests (2018).pdf

    Evergreen Alliance Staff
    By Beverly E. Law et al
    Strategies to mitigate carbon dioxide emissions through forestry activities have been proposed, but ecosystem process-based integration of climate change, enhanced CO2, disturbance from fire, and management actions at regional scales are extremely limited. Here, we examine the relative merits of afforestation, reforestation, management changes, and harvest residue bioenergy use in the Pacific Northwest. This region represents some of the highest carbon density forests in the world, which can store carbon in trees for 800 y or more. Oregon’s net ecosystem carbon balance (NECB) was equivalent to 72% of total emissions in 2011–2015. By 2100, simulations show increased net carbon uptake with little change in wildfires. Reforestation, afforestation, lengthened har- vest cycles on private lands, and restricting harvest on public lands increase NECB 56% by 2100, with the latter two actions contributing the most. Resultant co-benefits included water availability and biodiversity, primarily from increased forest area, age, and species diversity. Converting 127,000 ha of irrigated grass crops to native forests could decrease irrigation demand by 233 billion m3 per year. Utilizing harvest residues for bioenergy production instead of leaving them in forests to decompose increased emissions in the short- term (50 y), reducing mitigation effectiveness. Increasing forest carbon on public lands reduced emissions compared with storage in wood products because the residence time is more than twice that of wood products. Hence, temperate forests with high carbon densities and lower vulnerability to mortality have substantial potential for reducing forest sector emissions. Our analysis framework provides a template for assessments in other temperate regions.
    (2018) Land use strategies to mitigate climate change in carbon dense temperate forests.pdf

    Raven Tree
    By Curtis M. Bradley, Chad T. Hanson et al
    ABSTRACT: 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 investigat- ed 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.
    Does increased forest protection correspond to higher fire severity in frequent-fire forests of the western United States? (2016).pdf

    Raven Tree
    ABSTRACT: Wildfires across western North America have increased in number and size over the past three decades, and this trend will continue in response to further warming. As a consequence, the wildland–urban interface is projected to experience substantially higher risk of climate-driven fires in the coming decades. Although many plants, animals, and ecosystem services benefit from fire, it is unknown how ecosystems will respond to increased burning and warming. Policy and management have focused primarily on specified resilience approaches aimed at resistance to wildfire and restoration of areas burned by wildfire through fire suppression and fuels management. These strategies are inadequate to address a new era of western wildfires. In contrast, policies that promote adaptive resilience to wildfire, by which people and ecosystems adjust and reorganize in response to changing fire regimes to reduce future vulnerability, are needed. Key aspects of an adaptive resilience approach are (i) recognizing that fuels reduction cannot alter regional wildfire trends; (ii) targeting fuels reduction to increase adaptation by some ecosystems and residential communities to more frequent fire; (iii) actively managing more wild and prescribed fires with a range of severities; and (iv) incentivizing and planning residential development to withstand inevitable wildfire. These strategies represent a shift in policy and management from restoring ecosystems based on historical baselines to adapting to changing fire regimes and from unsustainable defence of the wildland–urban interface to developing fire-adapted communities. We propose an approach that accepts wildfire as an inevitable catalyst of change and that promotes adaptive responses by ecosystems and residential communities to more warming and wildfire.
    Adapt to more wildfire in western North American forests as climate changes (2016).pdf

    Evergreen Alliance Staff
    By John L. Campbell, Mark E. Harmon and Stephen R Mitchell
    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 fire-suppressed ecosystems, we found little credible evidence that such efforts have the added benefit of increasing terrestrial C stocks.
    (2012) Can fuel-reduction treatments really increase forest carbon storage in the western US by reducing future fire emissions?.pdf

    Raven Tree
    Mike D. Flannigan, Meg A. Krawchuk et al
    ABSTRACT: Wildland fire is a global phenomenon, and a result of interactions between climate–weather, fuels and people. Our climate is changing rapidly primarily through the release of greenhouse gases that may have profound and possibly unexpected impacts on global fire activity. The present paper reviews the current understanding of what the future may bring with respect to wildland fire and discusses future options for research and management. To date, research suggests a general increase in area burned and fire occurrence but there is a lot of spatial variability, with some areas of no change or even decreases in area burned and occurrence. Fire seasons are lengthening for temperate and boreal regions and this trend should continue in a warmer world. Future trends of fire severity and intensity are difficult to determine owing to the complex and non-linear interactions between weather, vegetation and people. Improved fire data are required along with continued global studies that dynamically include weather, vegetation, people, and other disturbances. Lastly, we need more research on the role of policy, practices and human behaviour because most of the global fire activity is directly attributable to people.
    Implications of changing climate for global wildland fire Mike D. Flannigan (2009).pdf

    Raven Tree
    By David B. Lindenmayer et al
    ABSTRACT: Does logging affect the fire proneness of forests? This question often arises after major wildfires, but data suggest that answers differ substantially among different types of forest. Logging can alter key attributes of forests by changing microclimates, stand structure and species composition, fuel characteristics, the prevalence of ignition points, and patterns of landscape cover. These changes may make some kinds of forests more prone to increased probability of ignition and increased fire severity. Such forests include tropical rainforests where fire was previously extremely rare or absent and other moist forests where natural fire regimes tend toward low frequency, stand replacing events. Relationships between logging and fire regimes are contingent on forest practices, the kind of forest under consideration, and the natural fire regime characteristic of that forest. Such relationships will influence both the threat of fire to human life and infrastructure and biodiversity conservation. We therefore argue that conservation scientists must engage in debates about fire and logging to provide an environmental context to guide considered actions.
    Effects of logging on fire regimes in moist forests David B. Lindenmayer (2009).pdf

    Raven Tree
    ABSTRACT: The emulation of natural disturbances such as fire is a prominent harvest management strategy for ecosystems in Canada’s boreal forest region, but the effect of harvesting on subsequent lightning fire occurrence has not been studied systematically in the mixedwood boreal forest. We quantified the relationship between annual patterns of lightning fire initiation, forest composition, lightning, and fire weather conditions over eight years (1994–2001) in a 60,000km2 region of actively harvested mixedwood boreal forest in western Canada. Our analyses illustrated that forest harvesting and burning had opposite effects on subsequent fire initiation, so harvest was not a surrogate for fire. Fire initiation increased in landscapes with more area harvested and decreased with area recently burned. Our data suggested that increased fire initiation was most pronounced in harvested stands up to a decade old, and there was some evidence that the effect might last as long as 30 years. We then used a dynamic fire- succession simulation model to quantify the long-term effects of these fuel-based relationships using two metrics. As expected, the first metric demonstrated that the number of years between disturbances was significantly less in stands that were harvested and then burned, than those that were burned and then burned again. However, the more revealing component of the simulations was an illustration that despite the strong, positive relationship between harvested areas and fire initiation, the area affected over the long-term by a reduced disturbance interval was relatively small. Accordingly, our study shows that spatiotemporal regulation of lightning fire initiation through harvesting activity results in a systematic accelerated frequency of disturbance that is novel to the mixedwood boreal system, but the area affected by these events amount to local peculiarities rather than broad-scaled regularities.
    Disturbance history affects lightning fire initiation in the mixedwood boreal forest- Observations and simulations Krawchuck (2008).pdf

    Evergreen Alliance Staff
    By Jonathan R. Thompson et al
    Debate over the influence of postwildfire management on future fire severity is occurring in the absence of empirical studies. We used satellite data, government agency records, and aerial photography to examine a forest landscape in southwest Oregon that burned in 1987 and then was subject, in part, to salvage-logging and conifer planting before it reburned during the 2002 Biscuit Fire. Areas that burned severely in 1987 tended to reburn at high severity in 2002, after controlling for the influence of several topographical and biophysical covariates. Areas unaffected by the initial fire tended to burn at the lowest severities in 2002. Areas that were salvage-logged and planted after the initial fire burned more severely than comparable unmanaged areas, suggesting that fuel conditions in conifer plantations can increase fire severity despite removal of large woody fuels.
    (2007) Reburn severity in managed and unmanaged vegetation in a large wildfire.pdf

    Raven Tree
    By Lori Daniels and Robert Gray
    ABSTRACT: What is the dominant disturbance regime in coastal British Columbia? In this literature review, we discuss the relative importance of fire versus canopy gaps as agents of disturbance affecting the structure and dynamics of unmanaged coastal forests in British Columbia. Our analyses focus on the province’s wet coastal temperate rain forests, specifically the Hypermaritime and Very Wet Maritime Coastal Western Hemlock (CWHvh and CWHvm) subzones, and the Wet Hypermaritime and Moist Maritime Mountain Hemlock (MHwh and MHmm) subzones. After reviewing the relationships between disturbance events, disturbance regimes, and stand dynamics, we critically assess the traditional classification of fire regimes in the wet coastal temperate rain forests, in part by differentiating between fire occurrence and mean return intervals. We provide four lines of evidence to reject the traditional view that stand-initiating fire at intervals of 250–350 years was the dominant disturbance regime in the wet coastal temperate rain forests of British Columbia. According to recent field research, historical fires were very infrequent in wet coastal temperate rain forests and were more likely low- and mixed-severity events, rather than stand-initiating fires. As an alternative to fire, we propose that fine-scale gap dynamics is the dominant process explaining the structure and dynamics of most unmanaged stands in the province’s wet coastal temperate rain forests. Improved understanding of the spatial and temporal attributes of disturbance regimes in coastal forests has important implications for sustainable forest management and conservation of biodiversity.
    Disturbance Regimes in Coastal British Columbia Daniels & Gray (2006).pdf

    Raven Tree
    By Craig R. Nitschke
    The emulation of natural disturbances is seen by many as an important management paradigm for achieving sustainable ecosystem management. To successfully emulate natural disturbances, managers must first have an understanding of the complex interactions that occur to the biophysical and chemical attributes of an ecosystem for both the natural and the ‘‘emulating’’ disturbance. The management of riparian ecosystems is an important issue faced by managers since the type of harvesting treatment can have a significant influence on the aquatic component. The removal or retention of riparian forests can have a direct influence on water quality and quantity, particularly on the smaller systems that are found at the headwaters of catchments, but do these treatments invoke a similar response as wildfire? To determine if emulation occurs, the affects of forest harvesting treatments and wildfire on temperature, water chemistry, summer stream flow, and sedimentation in headwater systems were compared using a meta-analysis. A statistically significant difference was found for temperature response between partial/selective harvesting and wildfire, but not after clear-cut harvesting. Water chemistry showed statistically significant differences for 11 out of 14 tested attributes, with dissolved organic carbon exhibiting the most marked difference. A significant difference was identified between clear-cut harvesting and wildfire for summer stream flow but not between wildfire and partial/ selective harvest systems. Forest harvesting operations were found to emulate sedimentation through forest roads but not harvest treatment. Partial/selective harvest systems may offer the greatest emulation congruency versus clear-cut harvest systems in terms of overall headwater response and recovery. Partial/selective harvest systems combined with prescribed burning may provide managers with the best solution when attempting to emulate wildfire in headwater systems and reduce the detrimental impact of perturbation on these systems.
    Does forest harvesting emulate fire disturbance? (2005).pdf

    Raven Tree
    By Carter Stone et al
    The USDA Forest Service is progressing from a land management strategy oriented around timber extraction towards one oriented around maintaining healthy forested lands. The healthy Forest Initiative promotes the idea of broadscale forest thinning and fuel treatments as an effective means for mitigating hazardous fuel conditions and, by extension, fire risk. Fuels mitigation is proactive while fire suppression is reactive and expensive. Costs associated with suppressing large wildfires, as occur in the western USA with annual regularity, are astronomical and routinely exceed fire suppression budgets. It is not difficult to demonstrate that treating forest fuels is more cost effective than suppressing forest fires on untreated lands. In addition, forest thinning is potentially profitable, or at least can recoup the cost of thinning, and may also produce safer conditions for those living in the wildland-urban interface zones. Thinning practices also facilitate wildland firefighting efforts for monitoring and controlling future fire incidents as well as for forest health management practices by state and federal forestry agencies. However, forest thinning and other fuel treatment strategies can take many different forms, some of which can do more harm than good when considered with other factors that influence wildfire behaviour, such as weather and terrain. One example of this issue can be seen in Montana during the 2003 fires. At the Cooney Ridge fire complex, an extensively and homogeneously logged watershed burned severely and uniformly due to remaining ground slash (which had attained low fuel moisture after overstory removal) and severe fire weather (low relative humidity and strong upslope winds). This contrasted with a mosaic of burn severities in an adjacent watershed with higher fuel loads yet greater heterogeneity in fuel distribution at the stand and landscape levels. Harvesting timber does not translate simply into reducing fire risk. Given the stochastic nature of fire weather events, and the complex terrain of most forested landscapes in the western USA, applying a variety of forest thinning and fuel treatment operations towards the goal of maintaining a diverse forest habitat mosaic, also constitutes a sensible fire risk mitigation strategy.
    Forest Harvest Can Increase Subsequent Forest Fire Severity (2004).pdf

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