Projected increases in western US forest fire despite growing fuel constraints

Abstract

Escalating burned area in western US forests punctuated by the 2020 fire season has heightened the need to explore near-term macroscale forest-fire area trajectories. As fires remove fuels for subsequent fires, feedbacks may impose constraints on the otherwise climate-driven trend of increasing forest-fire area. Here, we test how fire-fuel feedbacks moderate near-term (2021–2050) climate-driven increases in forest-fire area across the western US. Assuming constant fuels, climate–fire models project a doubling of forest-fire area compared to 1991–2020. Fire-fuel feedbacks only modestly attenuate the projected increase in forest-fire area. Even models with strong feedbacks project increasing interannual variability in forest-fire area and more than a two-fold increase in the likelihood of years exceeding the 2020 fire season. Fuel limitations from fire-fuel feedbacks are unlikely to strongly constrain the profound climate-driven broad-scale increases in forest-fire area by the mid-21st century, highlighting the need for proactive adaptation to increased western US forest-fire impacts.

Future climate risks from stress, insects and fire across US forests

“…Thus, these projections do not account for shifts in forest composition or distribution, interactions among risks, and carbon dioxide effects on plant drought stress. In particular, large‐scale impacts of fires, drought, or insects could substantially reduce biomass, and thus risk, although this is not likely to exert a material influence before the 2050s (Abatzoglou et al, 2021; Barbero et al, 2015). The risk projections also do not include impacts of land‐use management, considered to be a strong potential lever in fire risk (Smith et al, 2016) and to a lesser degree climate stress and insect risks.…”

“…In particular, large-scale impacts of fires, drought, or insects could substantially reduce F I G U R E 3 Risks for fire, climate stress-driven tree mortality, and insect-driven tree mortality (rows) averaged over the 2080-2099 period, separated by shared socioeconomic pathway (SSP) climate scenario (columns). Note that color-bars are substantially expanded relative to those in Figure 1 in order to visualise future projections that exceed historical risks biomass, and thus risk, although this is not to exert a material influence before the 2050s (Abatzoglou et al, 2021;Barbero et al, 2015). The risk projections also do not include impacts of land-use management, considered to be a strong potential lever in fire risk (Smith et al, 2016) and to a lesser degree climate stress and insect risks.…”

The 2019–2020 Australian forest fires are a harbinger of decreased prescribed burning effectiveness under rising extreme conditions

“…Although residual risk was greatly reduced in some areas after the 2019–2020 fire season, it remained substantial in other areas and was generally predicted to rise rapidly with fuel re-accumulation over the following five years. More work is needed to understand potential feedbacks between increasing fire activity, fuel accumulation and subsequent fire activity 8 .…”

Assessing Potential Safety Zone Suitability Using a New Online Mapping Tool

“…Burnovers are events in which flames overcome fire personnel, either on the ground or while in a vehicle, and entrapments are when firefighters become trapped by surrounding flames, unable to evacuate to safety [10]. As wildland fires increase in frequency, extent, and intensity, wildland firefighters may be put at heightened risk while working in the increasingly complex fire environment [11][12][13][14][15]. Passage of the Infrastructure Investment and Job Act in the US developing a requirement for federal agencies to "develop and adhere to recommendations for mitigation strategies for wildland firefighters to minimize exposure due to line-of-duty environmental hazards" further underscores the importance and continued policy relevance of wildland firefighter safety (see H.R.…”