Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests

Contemporary Wildfires Not More Severe Than Historically: More Fire of All Severities Needed to Sustain and Adapt Western US Dry Forests as Climate Changes

“…Earlier, high-severity fire from 1984-2012 was found to still be burning within the range of historical rates or was too low across 42 of 43 analysis regions, except California, in the 25.5 million ha of dry forests in the western USA [3]. However, new analysis, based on data from the U.S. government's Landfire program (www.landfire.gov, accessed on 4 November 2023), showed that recent fires in dry forests now have a higher percentage of high-severity fire than historically [4]. The percentage of fire of a particular severity is calculated from the percentage of total burned area that burned at a particular severity.…”

“…Alternatively, if there is recently just less low-to moderate-severity burned area, than historically, without more area burned at high severity, then restoring more low-to moderate-severity fire is all that is ecologically needed, as is supported by a large body of evidence. Several previous comparisons of recent and historical high-severity fire rates showed that area burned at high severity in dry forests is still lower recently than occurred However, new analysis, based on data from the U.S. government's Landfire program (www.landfire.gov, accessed on 4 November 2023), showed that recent fires in dry forests now have a higher percentage of high-severity fire than historically [4]. The percentage of fire of a particular severity is calculated from the percentage of total burned area that burned at a particular severity.…”

“…If more area of dry forests is burning at high severity recently than historically, then reducing high-severity fire is logical for sustainability, as concluded in Parks et al [4] and recent policy papers [5,6] based on a review by Hagmann et al [7]. Under the historical low-severity fire model used by these studies, changes in historical dry forests from logging, livestock grazing, and fire suppression allowed fuel buildup, leading to uncharacteristic high-severity fire [4][5][6][7].…”

“…However, Parks et al [4] recently added new evidence from government Landfire data (www.landfire.gov, accessed on 4 November 2023), although based on the rejected lowseverity fire model, showing that percent high-severity fire has increased. Landfire data, which include historical fire rates (e.g., fire rotation or mean fire interval) by fire severity (low, moderate, high) are reported to be based on expert opinions, informed by evidence, rather than based on primary scientific evidence itself [14].…”

Increases in understory plant cover and richness persist following restoration treatments in Pinus ponderosa forests

“…Low-severity, high-frequency fire is a natural process in many dry forests of the western United States and has long played a valuable role in important processes such as decomposition (Monleon, 1996), nutrient cycling (DeLuca & Sala, 2006), vegetative reproduction and germination of dormant seeds (Kerns & Day, 2018). Following a century of fire exclusion, expanded human populations, increased fuel biomass and continuity and human-altered climates have driven recent increases in fire size and the area burned at high severity, as well as shifts in fire seasonality (Balch et al, 2017;Parks et al, 2023). Such fire regime changes pose threats to the resilience and long-term persistence of many forests in the region and to the species that inhabit them, motivating ecological restoration treatments to reduce future fire severity by removing small trees and other hazardous fuels (Stephens et al, 2018).…”