2021 wildfire in Central California
The 2021 KNP Complex Fire was a large wildfire in Sequoia National Park and the Sequoia National Forest in Central California's Tulare County. After lightning ignited the Paradise and Colony fires in the southern Sierra Nevada on September 9, the twin blazes combined into the Complex and burned a total of . The fire was not declared contained until mid-December, after several atmospheric rivers delivered rain and snow to the mountains. The number of firefighting personnel reached more than 2,000 and firefighting costs surpassed $170 million.
The KNP Complex forced the communities of Three Rivers, Wilsonia, and Cedar Grove to evacuate, and caused the temporary closure of Sequoia and Kings Canyon National Parks while damaging roads, trails, and cabins within. The fire also heavily impacted the endangered giant sequoia, which grows in less than a hundred natural groves in the western Sierra Nevada. National Park Service scientists calculated that the KNP Complex Fire killed roughly 1,300–2,400 large giant sequoias (hundreds more died in the Windy Fire in the Sequoia National Forest, which burned contemporaneously). The fires are estimated to have killed three to five percent of the total population of large giant sequoias.
Background.
The KNP Complex Fire took place during a severe fire season for the western United States, and particularly for California. During the state's 2021 wildfire season nearly 2.6 million acres () burned: the second largest area on record after 2020. The national preparedness level hit the maximum level of 5 on July 14 and remained there until September 20, the longest period on record.6 Officials took drastic measures to try and limit new ignitions: between August 31 and September 15, the U.S. Forest Service’s Pacific Southwest Region closed all of California's national forests to public use because of fire conditions.
Fuels and climate.
In the decades preceding the fire, average temperatures in the Sierra increased measurably even as precipitation did not. This trend was driven partly by climate change. Climate change and consequent warming in California has helped produce hotter and more severe droughts, such as the one California endured between 2012 and 2016. Acute stress from that drought killed many trees in the Sierra Nevada, particularly at middling elevations.The lack of water also crippled trees' abilities to resist the predations of bark beetles, which resulted in "greatly elevated mortality" for many major tree species in Sequoia National Park, including the ponderosa pine, the sugar pine, the incense-cedar, and the white fir. Annual tree mortality rates nearly doubled in the park just between 1983 and 2004. A park representative estimated in 2021 that Sequoia and Kings Canyon National Parks held over one million beetle-killed trees that were helping drive the KNP Complex Fire.
California saw its second-driest water year ever in 2020–2021, exceeded only by that of 1923–1924. It was the driest ever water year on record for the southern Sierra Nevada, with of rainfall compared to the region's average of . The summer of 2021 was also California's hottest ever recorded. The hot and dry conditions kept vegetation moisture levels "critically low".24
The drought and dead trees added to the high levels of vegetation that had already accumulated in Sierra Nevada forests. Prior to European-American settlement, frequent fires of lower severity occurred, leaving most sequoia trees unharmed and aiding regeneration in the forest by consuming dry fuels. This ceased in the 20th century when the U.S. federal government began extinguishing every wildfire as a matter of policy. This led to elevated fuel loads in forests, including giant sequoia groves.
Not until the 1960s was fire reintroduced to some groves. While approximately used to burn naturally and annually in the Sequoia and Kings Canyon parks, as of 2022 the parks burned only around annually in prescribed burns. Much of the KNP Complex Fire footprint had no recent wildfire burn history.24 A 2023 study identified "old, large-diameter fuels like fallen logs" as the likely culprit for the fire's high intensity after analyzing radiocarbon signatures in samples of the smoke, consistent with prior research demonstrating that fire suppression and the resulting accumulation of fuels have contributed to elevated fire intensities in the Sierra Nevada.
Progression.
September 9–14.
On the night of September 9, a series of thunderstorms moved through California, generating more than 1,100 cloud-to-ground lightning strikes across the state by the following morning. Over 200 strikes occurred in Sequoia and Kings Canyon National Parks. On September 10, three lightning-ignited fires were discovered in Sequoia National Park. One of them, the Cabin Fire, was found near Dorst Creek and fully contained at only .
The other two fires were the Colony Fire near Colony Peak, burning in a mixed conifer forest west of the Giant Forest and north of the Kaweah River, and the Paradise Fire west of Paradise Creek, south of the Kaweah River and burning in chaparral in rugged terrain. Campgrounds and park roads nearby closed and suppression efforts began, with handcrews on the ground and water and fire retardant drops from the air. With the combination of difficult terrain and dry weather conducive to fire spread, park officials warned that "the fires have spread potential and could affect operations in the coming days or weeks." The Colony and Paradise fires grew overnight to and respectively, with no containment. On September 11 the two fires, though still discrete, were christened the KNP Complex Fire.
Ground crews on the Colony Fire were beleaguered by flames and many hazardous snags. Meanwhile, the Paradise Fire's challenging location mid-slope with no safety zones or easy access caused officials to resort to an aircraft-only strategy, hoping to use water and fire retardant drops to keep the fire north of Paradise Ridge and south of the Kaweah River. By September 13, the area burned surpassed for the Colony Fire and for the Paradise Fire. Evacuations were ordered for the Mineral King area, and warnings instituted for Three Rivers. The response was still hampered by the rough terrain, as officials noted that ground access to the Paradise Fire had proved "impossible" thus far. Only 130 personnel were engaged on the incident.
That night, the Paradise Fire spread down-slope to the north, crossing the Middle Fork of the Kaweah River and the Generals Highway. Park employees at the Ash Mountain Headquarters Complex and in employee housing nearby evacuated. Both fires expanded considerably over the course of the following day (September 14), taking the Paradise Fire's total burned acreage to more than and the Colony Fire to more than . Sequoia National Park closed to the public.
September 15–October 1.
On September 15 and 16, both fires grew moderately and on every flank. With the arrival of a Type 1 incident management team, the number of personnel on the incident grew to more than 400, even as the combined size of the two fires reached more than . As the Colony Fire moved within of the Giant Forest, containing the General Sherman tree and thousands of other giant sequoias, firefighters began to protect specific trees by removing vegetation from around their bases and covering parts of the trees in a protective foil wrap, usually used to protect structures and for firefighters' emergency shelters.
On September 17, the Colony and Paradise fires met and merged in the drainage of the Marble Fork of the Kaweah River. Smoke that had stifled the combined fire's northeastern portion cleared away, and the resulting ventilation allowed the fire to grow. The northern portion of the blaze pushed up and out of the Marble Fork into the Halstead Creek drainage in a "extreme head fire run", according to a National Park Service post-fire assessment, burning the entirety of the Suwanee Grove at almost entirely moderate to high severity. The fire also entered the westernmost edge of the Giant Forest grove for the first time, in the vicinity of the Four Guardsmen trees, but firefighters' protective efforts ensured all four survived. The total burned area reached by September 18 as the complex became one of the highest-priority wildfires in the nation.
The complex slowly grew to just over by September 21, causing Kings Canyon National Park to close. Portions of both parks east of the Pacific Crest Trail in the High Sierra remained open. As crews prepared for the fire's potential arrival in the Lost and Muir sequoia groves, the fire moved through the Giant Forest and reduced in intensity as it met areas that had already been treated with prescribed fire. Meanwhile, California Department of Forestry and Fire Protection (Cal Fire) personnel constructed control lines along Paradise Ridge to help check the fire's growth on its southern end.
In late September, a high-pressure system settled in place over the area: higher humidity levels and lower temperatures, combined with a thick smoke inversion, stifled fire behavior somewhat even as the lack of visibility prevented aircraft from flying. Despite this, on September 24, fire activity ticked up as flames moved down from the conifer forests into the grass and oak woodlands closer to the visitors center in the foothills, and leapt past firefighters and their control lines on Paradise Ridge. Burnout operations helped catch the fire in the Mineral King Road and Ash Mountain areas. A giant sequoia killed by the fire fell across the Generals Highway, blocking travel between the northern and southern portions of the fire until equipment could be mustered to cut through it.
During the last week of September, the fire grew by several thousand acres per day, driven by gusty west winds. As its footprint increased, mandatory evacuation orders were issued on September 30 for Eshom and Hartland Camp in Tulare County. These orders were expanded on October 1 to include Grant Grove Village, Wilsonia, and Cedar Grove in Kings Canyon National Park, and Big Meadows, Weston Meadows, and Quail Flat areas in Giant Sequoia National Monument. Approximately 158 homes were threatened between those in Sequoia National Park, in the Lodgepole area, and in the communities of Three Rivers and Hartland. On September 30, the fire crossed the North Fork of the Kaweah River, and entered the lower portion of the Pierce Creek drainage to the north. On October 1, the fire pushed up through Pierce Creek, over the lower parts of the Redwood Mountain ridge, and into Redwood Canyon,296 taking the total burned area to more than .
October 1–October 5.
For the next two days, the fire backed down into Redwood Canyon, burning through Big Springs Grove and making occasional runs up towards Big Baldy (a high granite ridge to the east).296 Redwood Mountain Grove was singled out for concern—park officials knew that its southern section lay on a steep slope and was littered with excess fuel. Firefighters had begun burnout operations in the grove on October 1. Officials also decided to apply an experimental polyacrylamide fire retardant gel to the canopies of the giant sequoias, and some was dropped on trees in Muir Grove. Smoky conditions kept aircraft away from Redwood Mountain Grove, preventing gel drops there, and before long the wildfire outpaced the firefighters' burnout operations.
By October 3, the fire's footprint spanned over . The fire spotted across Mineral King Road, provoking evacuation orders for Sierra King Drive, Hammond, and Oak Grove. That evening, part of the fire still burning near Pierce Meadow surged up the western side of Redwood Mountain. By morning, it had merged with a fire front burning up through Redwood Canyon, and the combined head of the fire burned the central portion of the canyon, scorching the southern part of Redwood Mountain Grove at high severity.296 The fire burned hot in the canyon, putting up convective pyrocumulus or pyrocumulonimbus clouds visible from the far side of the Sierra Nevada. In the sequoia grove itself the fire generated winds strong enough to strip bark and foliage from the sequoia trees, and flames likely climbed into the canopies of the sequoias, moving from tree to tree as a crown fire. The fire's run took it across Generals Highway near Stony Creek. The Tulare County Sheriff’s Office issued immediate evacuation orders for Mineral King Road and Mineral King Drive. The fire's intensity subsided upon reaching Big Baldy and parts of the grove that had previously been treated with prescribed fire.296 The Redwood Canyon area growth took the fire's total burned area to just shy of by October 5.
October 5–December 16.
Following the blow-up in Redwood Canyon, shifts in the weather began to enable firefighters to gain the upper hand. On