United States forestland is an important ecosystem type, land cover, land use, and economic resource that is facing several drivers of change including climatic. Because of its significance, forestland was identified through the National Climate Assessment (NCA) as a key sector and system of concern to be included in a system of climate indicators as part of a sustained assessment effort. Here, we describe 11 informative core indicators of forests and climate change impacts with metrics available or nearly available for use in the NCA efforts. The recommended indicators are based on a comprehensive conceptual model which recognizes forests as a land use, an ecosystem, and an economic sector. The indicators cover major forest attributes such as extent, structural components such as biomass, functions such as growth and productivity, and ecosystem services such as biodiversity and outdoor recreation. Interactions between humans and forests are represented through indicators focused on the wildland-urban interface, cost to mitigate wildfire risk, and energy produced from forest-based biomass. Selected indicators also include drought and disturbance from both wildfires and biotic agents. The forest indicators presented are an initial set that will need further refinement in coordination with other NCA indicator teams. Our effort ideally will initiate the collection of critical measurements and observations and lead to additional research on forest-climate indicators.
Wildfire is an annual threat for many rural communities in the Pacific Northwest region of the United States. In some severe events, evacuation is one potential course of action to gain safety from an advancing wildfire. Since most evacuations occur in a personal vehicle along the surrounding road network, the quality of this network is a critical component of a community’s vulnerability to wildfire. In this paper, we leverage a high-resolution spatial dataset of wildfire burn probability and mean fireline intensity to conduct a regional-scale screening of wildfire evacuation vulnerability for 696 Oregon and Washington rural towns. We characterize each town’s surrounding road network to construct four simple road metrics related to the potential to quickly and safely evacuate: (1) the number of paved lanes leaving town that intersect a fixed-distance circular buffer; (2) the variety of lane directions available for egress; (3) the travel area that can be reached within a minimum distance while constrained only to movement along the paved road network; and (4) the sum of connected lanes at each intersection for the road network within a fixed-distance circular buffer. We then combine the road metrics with two metrics characterizing fire hazard of the surrounding landscape through which evacuation will occur: (1) burn probability and (2) mean fireline intensity. By combining the road and fire metrics, we create a composite score for ranking all towns by their overall evacuation vulnerability. The most vulnerable towns are those where poor road networks overlap with high fire hazard. Often, these towns are located in remote, forested, mountainous terrain, where topographic relief constrains the available road network and high fuel loads increase wildfire hazard. An interactive map of all road quality and fire hazard metrics is available at https://www.fs.fed.us/wwetac/brief/evacuation.php.
Although a natural ecological process, wildfire in unhealthy forests can be uncharacteristically destructive. Fuel treatments—such as thinning, mowing, prescribed fire, or managed wildfire—can help reduce or redistribute the flammable fuels that threaten to carry and intensify fire. Using both field-tested data and computer simulations, Pacific Northwest Research Station scientists are addressing critical questions such as Are we treating enough of the landscape to restore fire-adapted forests? Are fuel treatments effective at changing fire behavior? Together with land managers, fuel planners, and other partners, our scientists are helping public land management agencies move toward a future of fire-resilient forests and communities.
Many socioeconomic constraints exist for biomass removals from federal lands in the western U.S. We examine several issues of importance, including biomass supply chains and harvesting costs, innovative new uses for bioenergy products, and the policy framework in place to provide incentives for biomass use. Western states vary greatly in the extent and utilization of forest resources, the proportion of land under federal ownership, and community and stakeholder structure and dynamics. Our research—which focused on the socioeconomic factors associated with biomass removal, production, and use—identified several important trends. Long-term stewardship projects could play a role in influencing project economics while being conducive to private investment. State policies are likely to help guide the growth of biomass utilization for energy products. New markets and technologies, such as biofuels, for use in the aviation industry, torrefied wood, mobile pyrolysis, and wood coal cofiring could greatly change the landscape of biomass use. Social needs of residents in wildland urban interfaces will play an important role, especially in an era of megafires. All of these trends—including significant unknowns, like the volatile prices of fossil energy—are likely to affect the economics of biomass removal and use in western forests.
Simulating an advancing fire front may be achieved within a Lagrangian or Eulerian framework. In the former, independently moving markers are connected to form a fire front, whereas in the latter, values representing the moving front are calculated at points within a fixed grid. Despite a mathematical equivalence between the two methods, it is not clear that both will produce the same results when implemented numerically. Here, we describe simulations of fire spread created using a level set Eulerian approach (as implemented in the wildland-urban interface fire dynamics simulator, WFDS) and a marker method (as implemented in FARSITE). Simulations of surface fire spread, in two different fuels and over domains of increasing topographical complexity, are compared to evaluate the difference in outcomes between the two models. The differences between the results of the two models are minor, especially compared with the uncertainties inherent in the modelling of fire spread
Predicting wildfire disasters presents a major challenge to the field of risk science, especially when fires propagate long distances through diverse fuel types and complex terrain. A good example is in the western US where large tracts of public lands routinely experience large fires that spread from remote wildlands into developed areas and cause structure loss and fatalities. In this paper we provide the first comprehensive assessment of where public wildlands potentially contribute wildfire exposure to communities in the 11 western US states. We used simulation modeling to map and characterize the composition of the source landscapes (firesheds) and recipient communities in terms of fuels, fire behavior and forest management suitability. The information was used to build a prototype investment prioritization framework that targets highly exposed communities where forest and fuel management activities are feasible. We found that simulated wildfires ignited on national forests can potentially affect about half of the communities in the western US (2560 out of 5118), with 90% of exposure affecting the top 20% of the communities (n=516). Firesheds within national forests, defined as areas that have the potential to expose communities to fire, were estimated at 35 million ha (62% of the total national forest area), and were almost three times larger than the affected community lands. Large contiguous areas of wildfire transmission were evident on a number of national forests. Only 22% of the fireshed area is forested, fireadapted, and lies within land management designations that allow mechanical fuels management. The methods demonstrate how cross-boundary exposure can be factored into prioritizing federal investments in hazardous fuels reduction on national forests in concert with community protection measures. The results can also help scale wildfire governance systems to match the geography of risk from large wildfire events, which augments existing assessments that do not explicitly identify the source of risk to communities.
In this report we provide a framework for assessing cross-boundary wildfire exposure and a case study application in the western U.S. The case study provides detailed mapping and tabular decision support materials for prioritizing fuel management investments aimed at reducing wildfire exposure to communities located proximal to national forests. The work was motivated by a number of factors, including a request from U.S. Department of Agriculture Undersecretary James Hubbard (Natural Resources and Environment) to assess community wildfire risk specifically from Forest Service lands, language in the 2018 omnibus bill (Public Law 115-141) calling for a national assessment of wildfire risk to communities, and newer shared stewardship initiatives (Clavet 2018). We used national FSim simulation outputs to (1) estimate cross-boundary wildfire among major land types (Federal, State, private); (2) quantify structure exposure to all western communities; (3) map sources of community wildfire exposure (firesheds); (4) characterize firesheds in terms of management opportunity and fuels; and (5) prioritize communities based on integration of exposure and fireshed characteristics. The study revealed that 1,812 communities in the western U.S. could potentially be significantly impacted by future wildfires (more than 1 structure per year on average). Ignitions on national forest lands will most likely affect 516 of these 1,812 communities (more than one structure per year on average). Of the total exposure, ignitions on national forest lands will expose an estimated 4,000 structures (21 percent of total) in the western U.S. per year on average. Due to administrative restrictions on national forest lands, only about half of the total exposure from national forest lands (2,200 structures) originates on lands where mechanical treatments and prescribed fire are either allowed or ecologically appropriate. The framework can guide future efforts aimed at quantifying community and other cross-boundary exposure situations, and the outputs can be used to help identify shared stewardship projects, and prioritize fuel and other management activities within public land management agencies.