Abstract  The historical development of practical and economic wildland fire management policies is briefly traced. The main emphasis of the paper is on the economic approach. The economic theory is a function of three elements: cost, production, and net present loss. The production function is the key element of the theory. Costs are classified into variable and fixed, the latter being further subdivided into short- and long-run. The need for using net present value with respect to the latter is discussed. As defined in this paper, there are three factors of production: fire occurrence, fire control, and fuel management. A theoretical procedure for determining the optimum mix of production factors is discussed. Net present loss consists of damage and benefits. There are three categories of damage, based on the person to whom the damage accrues: the owner, the user, and others. Actual value lost to each category is affected by substitutability and a risk premium. The importance of market processes in relation to damage assessment is also considered. Lastly, the effect of beneficial impacts of wildland fire is discussed.

Abstract  As a result of climate change and past management practices, wildfires are becoming larger and occurring more frequently than ever before in the Western U.S. In order to mitigate the effects of this growing threat, fire management agencies such as the U.S. Forest Service have encouraged residents in at-risk communities to protect their homes, property and communities by adopting Firewise recommendations. Using annual random sample household surveys conducted in fire-prone central Oregon from 2011 to 2013, this study examines the impact of wildfire events (i.e., wildfire exposure and evacuation), risk perception, wildfire plan informedness, proximity to wildlands, and various demographic factors on resident Firewise behavior participation. Findings indicate that residents who have experienced a wildfire event, who are familiar with their county’s Community Wildfire Protection Plan, who perceive wildfire risk to their community, and who live in proximity or within a wildland area, were significantly more likely to engage in Firewise behaviors than those residents without these experiences, orientations or household locations.

Abstract  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.

Abstract  Mechanical treatment of vegetation is done on public and private lands for many possible reasons, including enhancing wildlife habitat, increasing timber growth of residual stands, and improving resistance to damaging pests. Few studies, however, have focused on the circumstances under which mechanical wildfire hazard reduction treatments can yield positive net economic wildfire benefits for landowners and managers. This study describes an economic assessment tool built from a representative area sample frame inventory of hazardous and potentially treatable timberland in twelve western states of the U.S. Base case parameter assumptions about values at risk, timber product prices, stand re-growth following treatment and wildfire impacts enable an initial estimate of the amount of timberland with positive discounted expected net economic benefits under four policy scenarios. These assumptions are then varied in a Monte Carlo simulation to provide some bounds of uncertainty around base case levels. A policy that allowed optimal prescriptions and product sales and which incorporates wildfire costs and benefits would result in more than 25% of treated area with positive net benefits. This is reduced somewhat if wildfire reduction costs and benefits are not considered, and reduced again to 14% when large trees are excluded from product sales. A policy that prohibits sale of products from these treatments results in less than 1% of area with positive net benefits.

Abstract  Observations of increasing global forest die-off related to drought are leading to more questions about potential increases in drought occurrence, severity, and ecological consequence in the future. Dry soils and warm temperatures interact to affect trees during drought; so understanding shifting risks requires some understanding of changes in both temperature and precipitation. Unfortunately, strong precipitation uncertainties in climate models yield substantial uncertainty in projections of drought occurrence. We argue that disambiguation of drought effects into temperature and precipitation-mediated processes can alleviate some of the implied uncertainty. In particular, the disambiguation can clarify geographic diversity in forest sensitivity to multifarious drivers of drought and mortality, making more specific use of geographically diverse climate projections. Such a framework may provide forest managers with an easier heuristic in discerning geographically diverse adaptation options. Warming temperatures in the future mean three things with respect to drought in forests: (1) droughts, typically already unusually hot periods, will become hotter, (2) the drying capacity of the air, measured as the vapor pressure deficit (VPD) will become greater, and (3) a smaller fraction of precipitation will fall as snow. More hot temperature extremes will be more stressful in a direct way to living tissue, and greater VPD will increase pressure gradients within trees, exacerbating the risk of hydraulic failure. Reduced storage in snowpacks reduces summer water availability in some places. Warmer temperatures do not directly cause drier soils, however. In a hydrologic sense, warmer temperatures do little to cause "drought" as defined by water balances. Instead, much of the future additional longwave energy flux is expected to cause warming rather than evaporating water. Precipitation variations, in contrast, affect water balances and moisture availability directly; so uncertainties in future precipitation generate uncertainty in drought occurrence and severity projections. Although specific projections in annual and seasonal precipitation are uncertain, changes in inter-storm spacing and precipitation type (snow vs. rain) have greater certainty and may have utility in improving spatial projections of drought as perceived by vegetation, a value not currently captured by simple temperature-driven evaporation projections. This review ties different types of future climate shifts to expected consequences for drought and potential influences on physiology, and then explains sources of uncertainty for consideration in future mortality projections. One intention is to provide guidance on partitioning of uncertainty in projections of forest stresses.

Abstract  During a wildfire, smoke can make the outdoor air unhealthy to breathe. Local officials may advise you to stay indoors during a smoke event. You should be aware that some of the smoke from outdoors can enter your home and make it unhealthy to breathe indoor air, too. If you are close to a wildfire, the fire itself, as well as heavy smoke and ash, can pose serious, immediate risks to your safety and health. You and your family should be prepared to evacuate immediately if told to do so. Farther from a wildfire, you may be exposed to smoke even if the fire itself is far away. Smoke is made up of a complex mixture of gases and fine particles produced when wood and other organic materials burn. The biggest health threat from smoke is from fine particles. These microscopic particles can get into your eyes and respiratory system – whether you are outdoors or indoors, where they can cause health problems such as burning eyes, runny nose, and illnesses such as bronchitis. Fine particles also can aggravate chronic heart and lung diseases - and even are linked to premature deaths in people with these conditions. If you are healthy, you're usually not at a major risk from short-term exposures to smoke. Still, it's a good idea to avoid breathing smoke – both outdoors and indoors – if you can help it. Learn more about the health effects of wildfire smoke. This page provides helpful information to reduce your exposure to wildfire smoke inside your home.

Abstract  EPA researchers initiated a citizen science project called Smoke Sense. This project has two broad objectives. The first is to increase awareness of the known health effects associated with exposure to wildfire smoke. The second is to further advance the scientific understanding of that relationship, specifically to: - Understand the subclinical health impacts of wildland fire smoke - Discover how people protect their health during smoke exposure - Develop effective strategies to communicate health risks from smoke exposure Individuals who want to contribute to science can participate in the study by using the Smoke Sense app, a free mobile application on the Google Play™ Store and the Apple App™ Store. Smoke Sense is available in both English and Spanish.   The study is the first of its kind known to use a mobile application to evaluate health effects from wildland fires experienced by those who participate, and to test whether health risks can be communicated effectively through resources and engagement delivered with the app.  Smoke Sense app users participate anonymously and their identities are not captured.

Abstract  Administrative planning rules and legal challenges can have significant economic impacts on timber salvage programs on public lands. This paper examines the costs of the delay in salvage caused by planning rules and the costs associated with the volume reductions forced by legal challenges in one case study. The fires on the Bitterroot National Forest in the northern Rocky Mountains in the United States burned 124,250 ha in the summer of 2000, killing valuable timber. A proposal to salvage about 15% of the burned area, containing 0.8 million m3 (176 million board feet) of the damaged timber, was challenged in court, resulting in a mediation plan salvage amount of 0.27 million m3 (60 million board feet). Administrative planning requirements also delayed the initiation of salvage to 2003. Because timber decays following death and damage, the costs of delay can be quantified. We evaluate the costs of both reducing the salvage volume due to the litigation and the losses due to decay from the administrative delay. Simulations show that the court settlement plan created through legal challenge resulted in an $8.5 million loss to the U.S. treasury and an $8.8 million (65%) loss in net welfare under the base case market assumptions. The delay in salvaging the agreed upon salvage amount from 2001 to 2002 reduced revenues from salvage to the U.S. treasury by $1.5 million (25%) and potential welfare benefits by the same amount, under base case assumptions of market sensitivities to prices.

Abstract  This site is part of an effort by the U.S. Interagency Wildland Fire Air Quality Response Program to track COVID and air quality across the United States. The data, report, and assessment category levels are provided only for informational use and convenience and should not be considered as guidance or authoritative. Broader analyses should be performed before any decisions are made. The data presented here may contain significant errors and should be verified. This page is experimental; use at own risk.

Abstract  Mor humus samples from separate plots in a field-liming experiment in southern Sweden were incubated in a leaching experiment. Lime applications of 0.16, 0.35, and 0.88 kg/m 2 dolomite lime were made 7 y before sampling. The leachates from the two highest lime applications had a pH of 7.0 and 5.3, respectively. The control and the lowest lime application had a pH of 3.9. Humus material receiving the largest lime application also showed the highest level of dissolved organic carbon (DOC) leaching (180 mg DOC/L) during the first 100 d of the experiment, probably owing to the increased negative charge caused by the high pH, which increased the solubility. The DOC concentration decreased in all treatments towards the end of the experiment owing to an increase in protonation caused by nitrate formation (nitrification). The C/S ratio in the organic matter of the leachates from the limed humus was lower than that in the control leachates. A positive correlation between DOC leaching and biological activity, measured as soil respiration, was found in humus material that had received the two highest lime applications.

Abstract  Extreme wildfire events are becoming more common and while the immediate risks of particulate exposures to susceptible populations (i.e., elderly, asthmatics) are appreciated, the long-term health effects are not known. In 2017, the Seeley Lake (SL), MT area experienced unprecedented levels of wildfire smoke from July 31 to September 18, with a daily average of 220.9 μg/m3. The aim of this study was to conduct health assessments in the community and evaluate potential adverse health effects. The study resulted in the recruitment of a cohort (n = 95, average age: 63 years), for a rapid response screening activity following the wildland fire event, and two follow-up visits in 2018 and 2019. Analysis of spirometry data found a significant decrease in lung function (FEV1/FVC ratio: forced expiratory volume in first second/forced vital capacity) and a more than doubling of participants that fell below the lower limit of normal (10.2% in 2017 to 45.9% in 2018) one year following the wildfire event, and remained decreased two years (33.9%) post exposure. In addition, observed FEV1 was significantly lower than predicted values. These findings suggest that wildfire smoke can have long-lasting effects on human health. As wildfires continue to increase both here and globally, understanding the health implications is vital to understanding the respiratory impacts of these events as well as developing public health strategies to mitigate the effects.

Abstract  Wood ash fertilization increases the pH and concentration of dissolved organic carbon (DOC) in the soil solution and enhances the activity of soil microorganisms. However, it is unknown whether DOC or pH is primarily responsible for the increase in microbial activity. We designed an experiment to separate the effects of DOC and/or pH on soil microbial activity using suspensions of humus extracts and bacteria that had not previously been exposed to wood ash fertilization. After a 3-week incubation, DOC extracts were obtained from control (DOCC) and ash (DOCA) treatments with carbon concentrations of 9.1 and 32.5 mg C l−1, respectively. These extracts were supplied to bacterial suspensions at concentrations of 0 and 5 mg C l−1. We controlled for pH by matching adjustments, i.e. the original pH of the DOCC extract was 4.5 and its adjusted pH was 6.9, whereas the DOCA extract was pH 6.9 originally and pH 4.5 adjusted. The relative bacterial growth rate (RBGR), as measured by 3H-thymidine incorporation, increased in suspensions of 5 mg C l−1 DOC as compared to control suspensions of 0 mg C l−1. At pH 6.9, RBGR was higher for both DOC extracts than at pH 4.5. These results suggest that both DOC and pH influence microbial activity. As the growth rate at pH 6.9 with DOCA was higher than with DOCC, the quality of the DOC extract must also play a role since the carbon concentration was controlled for. The decrease in relative abundance of hydrophobic and hydrophilic acids in DOCA compared to DOCC indicates a quality shift. As measured by DGGE banding patterns, the bacterial community structure changed over the course of the 24-h experiment in the following three trials, all of which received 5 mg C l−1: DOCC at pH 6.9 and DOCA at pH 4.5 and 6.9. These results demonstrate that both the DOC origin (control vs. ash) and the pH influence a subset of the bacterial community.

Abstract  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.

Abstract  Across the globe, rising temperatures and altered precipitation patterns have caused persistent regional droughts, lengthened fire seasons, and increased the number of weather-driven extreme fire events. Because wildfires currently impact an increasing proportion of the total area burned, land managers need to better understand reburns – in which previously burned areas can modify the patterns and severity of subsequent fires. For example, knowing how long past fire boundaries can function as barriers to fire spread may empower decision-makers to manage some wildfires as large-scale fuel treatments, or alternatively, determine where prescribed burning or strategic wildfire management are required. Additionally, a clear understanding of how prior burn mosaics influence future fire spread and burn severity is critical knowledge for landscape and fire-dependent wildlife habitat planning under a rapidly changing climate. Here, we review published studies on reburns in fire-adapted ecosystems of the world, including temperate forests of North America, semi-arid forests and rangelands, tropical and subtropical forests, grasslands and savannas, and Mediterranean ecosystems. To date, research on reburns is unevenly distributed across the world with a relative abundance of literature in Australia, Europe and North America and a scarcity of studies in Africa, Asia and South America. This review highlights the complex role of repeated fires in modifying vegetation and fuels, and patterns of subsequent wildfires. In fire-prone ecosystems, the return of fire is inevitable, and legacies of past fires, or their absence, often dictate the characteristics of subsequent fires.

Abstract  Wildland fire smoke is a complex mixture of air contaminants that have the potential cause adverse health effects. Individuals can be exposed occupationally if they work as wildland firefighters or public exposure from ambient air that is contaminated with smoke from a nearby or distant wildland fire. Previous studies of public exposure to smoke have suggested that wildland fire smoke can cause adverse respiratory health effects and possibly increased mortality and cardiovascular health effects. What the research means for healthy workers is less clear. For example, in wildland firefighters, minor decrements in lung function may be at least partially reversible after periods of recovery (no exposure), but even temporary clinically significant adverse effects from occupational exposures are unacceptable outcomes. This work combines a comprehensive literature review with extensive smoke exposure concentration data for wildland firefighters to estimate health risks specific to wildland fire smoke. First, we conducted a literature review to identify smoke components that present the highest health hazard potential, the mechanisms of their toxicity, and reviewed epidemiological studies to identify the current gaps in knowledge about the health impacts of wildland fire smoke exposure for firefighters and the public. Next, we examined wildland firefighter exposures, explored predictors of smoke exposures to determine factors influencing smoke exposure for wildland firefighters and estimated exposure to air pollutants using carbon monoxide (CO) as an indicator pollutant. Lastly, we estimated disease risk in wildland firefighters for exposure to particulate matter from smoke using firefighter specific breathing rates with existing exposure response relationship information for risk of lung cancer, ischemic heart disease and cardiovascular disease from cigarette smoking, which produces particulate matter with a similar size range. From the literature review, we found that respiratory events measured in time series studies as incidences of disease-caused mortality, hospital admissions, emergency room visits and symptoms in asthma and chronic obstructive pulmonary disease patients are the health effects that are most commonly associated with public exposure to wildland fire smoke. A few recent studies have also determined associations between acute wildland fire smoke exposure and cardiovascular health end-points. From this review, we concluded that there remains a need for research on acute and longer term effects of wildland fire smoke exposure. The health effects of acute exposures beyond susceptible populations and the effects of chronic exposures experienced by the wildland firefighter are largely unknown. Longitudinal studies of wildland firefighters during and/or after their firefighting career could help elucidate some of the unknown health impacts of cumulative exposure to wildland fire smoke, establish occupational exposure limits, and help determine the types of exposure controls that may be applicable to the occupation. We found that among 83 firefighters at prescribed burns, and 417 at project wildfires, the Occupational Safety and Health Administration (OSHA) 8-hour exposure level of 50 ppm for CO was exceeded 3.5 percent of the time at prescribed fires and 5.6 percent of the time at project fires. Adjustments recommended for altitude, work rate and duration of exposure would increase these percentages. We identified that crew type, main work task and duration, and downwind position from the fire were factors that influenced exposure to CO and respirable particulate matter, but only main task and duration were important predictors for respirable crystalline silica exposure. Linear regression results indicated that CO measurement is a reasonably useful real-time gauge of the inhalation hazard from smokederived particulate matter. The exposure data also found that respirable crystalline silica was a soil-derived hazard that exceeded shift-average OSHA Permissible Exposure Limits from 6.7% to as much as 28% of the time, depending on incident type. Using epidemiology studies to understand the exposure-response relationship for PM, we found that firefighters were at an increased risk for long-term health effects from smoke exposure. The risk for lung cancer mortality increases nearly linearly with exposures over time and is more strongly influenced by exposure duration than are the risks of death from cardiovascular or ischemic heart disease. On the other hand, the risk of cardiovascular mortality rises steeply for doses in the range we estimated for firefighter exposures but flattens out at higher exposures to PM. The data presented in this paper clearly identify the crews and activities most likely to exceed occupational exposure limits and firefighters may have a an increased health risk from smoke exposures.