Ignited on July 24, 2024 by arson near Chico, California, the Park Fire burned 429,000 acres with much of it in Lassen National Forest. The center of this massive fire was the Ishi Wilderness, which last burned extensively in 1990--this was the 131,000 acre Campbell Fire--and smaller fires burned in 1994, 2013 and 2014. Historically, this entire area burned with high frequency, which regularly kept fuels in check. Without regular fire, this ecosystem accumulates fuel which then can burn at uncharacteristically high severity during extreme weather. 

These maps show initial fire severity for the Park Fire, including WorldView 3 imagery immediately after the fire burned for the southern part of the burn that includes part of the Ishi Wilderness.  Also notable in summer 2024 was insect defoliation, that apparently was caused by the Douglas Fir Tussock Moth in the northeastern part of the burn. This defoliation occurred shortly before the fire passed through and appears to not have affected fire severity.  Within mid and higher elevations that burned there are notable differences in fire severity to trees. Low-severity fire was extensive near streams, and these topographic features often functioned as refugia from higher severity fire, even though they apparently burned in the understory. There may be delayed mortality, however. There also appear to be extensive areas of open pine woodland with mature trees that died and other areas with possible survival. Future imagery (in 2025) will show the extent of tree mortality more accurately.