How forest management changed the course of the Washburn fire and the fate of Yosemite’s giant sequoias (Sequoiadendron giganteum)

Abstract

Background The Washburn fire started on July 7, 2022 in the lower Mariposa Grove in Yosemite National Park, posing immediate threats to the iconic giant sequoias (Sequoiadendron giganteum), critical Pacific fisher (Pekania pennanti) habitat, and the community of Wawona. The wildfire quickly gained national attention and the public followed Yosemite’s firefighting efforts closely. In the aftermath of the Washburn fire, we evaluate how decades of fire management and recent roadside thinning in the Park shaped the tactics and outcomes of this wildfire. Fuels reduction and prescribed fire have been at the core of Yosemite’s fire management program since the 1970s and much of this activity has been concentrated in the two areas where firefighting operations were most successful in protecting key resources. We use long-term fire effects monitoring data, airborne light detection and ranging data, and operational perspectives to link together science, management, and fire operations. Results Successful initial attack and suppression efforts kept fire out of the Mariposa Grove and the community, where topography and the distribution of heavy fuels largely drove fire behavior throughout the course of the fire. We demonstrate the cumulative effects of decades of fuels treatments in reducing two major drivers of fire behavior – tree density and fuel load – and highlight substantially lower ladder fuels and fire severity in treatment units compared to untreated areas within the Washburn fire footprint. Conclusions We show how repeated prescribed fire and fuels treatments can promote forest structure indicative of frequent-fire regimes, moderate extreme fire behavior, improve the ability to protect key resources of concern, and increase human safety in the face of unplanned wildfire. Strategically placed prescribed fire and fuels treatments surrounding the Washburn fire were key considerations in wildfire suppression tactics and were instrumental in protecting the Mariposa Grove.

Pyrogeography in flux: Reorganization of Australian fire regimes in a hotter world

“…Hysteresis in climate-plant-fire relationships or changes in human fire management may either help resist or exacerbate state change (Bowman et al, 2022). Such emerging management strategies include reintroducing herbivores to reduce fuels (Johnson et al, 2018), using low-flammability plants as green fire breaks (Cui et al, 2019), mechanically removing woody fuels (Furlaud et al, 2023), letting fires burn under appropriate conditions (Boisramé et al, 2017), reseeding populations that collapsed under frequent fire (Bassett et al, 2015), rapidly deploying fire-fighting teams to protect sensitive biodiversity (Hankin et al, 2023;Kelly et al, 2020), and assisting forests to reach lower-flammability mature states (Zylstra et al, 2022(Zylstra et al, , 2023. Crucially, fire management will likely benefit from the ancient wisdom of Indigenous-led fire management, involving fine-tuned application of fire when each vegetation type requires it (Bowman & Sharples, 2023;Steffensen, 2020).…”

Forest thinning and prescribed burning treatments reduce wildfire severity and buffer the impacts of severe fire weather

“…The primary goal of forest thinning and prescribed burning for fuel reduction, hereafter fuel treatment, is to mitigate the effects of wildfire on ecological and human communities by moderating fire behavior and reducing fire severity outcomes (Agee & Skinner 2005;Finney 2001). Reducing wildfire severity is a key management objective in dry mixed conifer forests in the western USA, where over a century of fire exclusion has increased fuel loadings (Hankin et al 2023;Knapp 2015;Knapp et al 2013;Stephens et al 2015) and aridity associated with climate change is contributing to more intense fire behavior (Abatzoglou & Williams 2016). Together, such changes have resulted in larger and higher severity fires than those that were experienced historically (Hagmann et al 2021;Parks & Abatzoglou 2020).…”

Forest restoration and fuels reduction work: Different pathways for achieving success in the Sierra Nevada

“…In contrast, burning or thinning alone had either lesser or no effects, compared with untreated controls. A recent study found that prescribed fire and forest thinning were critical in preventing high-severity wildfires from impacting the Mariposa giant sequoia (Sequoiadendron giganteum) grove in Yosemite National Park (Hankin et al, 2023) further adding to the literature of the effectiveness of fuel treatments.…”