File:Washburn Fire in Yosemite National Park (MODIS 2022-07-13).jpg

English: On the afternoon of July 7, 2022, a fire was spotted burning near the Washburn Trail in the Mariposa Grove area of Yosemite National Park, California, triggering a rapid full-attack response from firefighters. With 1,045 personnel active, the Washburn file has grown to 3,516 Acres as of July 12 and is 17 percent contained. The cause is under investigation, but the Yosemite Superintendent has been quoted as explaining that the Washburn Fire is considered a “human start”, as there was no lightning on the day it ignited.

The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of the Washburn fire on July 11. Large red hot spots mark the area where the thermal bands on the instrument detected high temperatures. Combined with the copious gray smoke, which rises and blows northwestward from the scene, the hot spots represent the location of the actively burning fire.

According to a report published on InciWeb Incident Information System on the evening of July 12, “The area in which the fire is burning contains a very heavy accumulation of fuels (trees in various forms and stages) on the ground as well as part of the understory. This old growth habitat is a combination of dead large diameter trees and timber litter on the ground (many feet thick in some cases) in combination with thick growing conifers and shrubs, much of which has been largely untouched for many decades. The more than 500 mature giant sequoias of the Mariposa Grove are adjacent to these fuels and have so far avoided serious damage from the Washburn Fire. Most of these trees are over 2000 years old and have experienced fire many times throughout their lives.”

Giant sequoias are equipped with a thick and fire-resistant bark, making them able to survive low intensity blazes. The trees also require intermittent fire for reproduction—the seeds only germinate after a fire. Fire also clears the underbrush and competitive plants, creating fertile soil that allows seeds to take root.

The fire and response activity has caused closure of part of Wawona Road (Highway 41) and the Mariposa Grove until further notice. Some residents of the town on Wawona have had to evacuate. Most of the park remains open to visitors, but heavy smoke may be experienced at times.

Weather plays an important role in fire suppression or growth. Unfortunately, hot, dry weather is expected to continue in the region for the next several days. This will result in active to very active fire behavior in heavy dead and down fuels. Growth of the fire, especially on the east flank, is to be expected in the short term, despite full-suppression efforts. Some of the large trees, such as the Grizzly Giant, do have sprinkler systems already in place, and this should assist in protecting at least individual trees.