The General Sherman giant sequoia and surrounding groves of ancient giant sequoias are in danger of being scorched by wildfires.

The KNP Complex Fire – made up of the Colony and Paradise Fires – is burning in the southern Sierra Nevada mountain range east of Visalia, California as of September 20, 2021. The complex, started by lightning on the morning of September 10, has grown to 23,743 acres within the Sequoia and Kings Canyon National Parks. The fire is at 0 percent containment.¹

The nearby Windy Fire, located in the Giant Sequoia National Monument, is being treated by firefighting units as a separate fire from the KNP Complex Fire. It is also a major threat to the region and to the Tule River Indian Reservation.² At 23,801 acres, it is only 4 percent contained.

Though the fires reached as far as Long Meadow Grove, home to the Trail of 100 Giant Sequoias, it is unknown whether any trees were damaged or lost. The park and part of nearby Three Rivers were evacuated last week.

The largest trees in the world, giant sequoias are usually adapted to some fires as sequoia bark can resist burning, heal with new growth, and the trees are insulated against heat. However, too many fires over a sequoia’s lifetime can prevent its bark from healing and result in death. Bark beetles, drought, and fire at the base of sequoia trees can also result in their deaths.

The largest known single-stem tree in the world, General Sherman is 275 feet tall and believed to be between 2,300 and 2,700 years old.³ Firefighters have wrapped up the tree in protective foil in hopes of protecting it from the fire.

Hazardous air quality envelopes mountains

Air quality declined sharply in towns surrounding the fire, particularly for mountain and valley communities along the Kaweah River and further south to Lake Isabella. Kernville reported dangerously high concentrations of PM2.5 resulting in an air quality of 538 – far above the lowest level for “hazardous” air, 301.

Hazardous air quality, the worst air quality possible on the air quality index, was also measured in Camp Nelson, near the Giant Sequoia National Monument.

Further north in Kaweah and Three Rivers, air quality ranged from unhealthy to very unhealthy – not quite hazardous, but still dangerous enough to endanger the general public.

Wildfire smoke can drift thousands of miles from its source. Smoke from the complex of fires may be affecting air quality as far south as Lancaster.

Pictured: Air quality in the southern Sierra Mountains ranged from unhealthy to hazardous in communities near the fire. General Sherman is located near Red Fir. Source: IQAir

Wildfire smoke carries toxic airborne pollutants on the wind. Particulate matter is the biggest component found in smoke, including PM2.5 and ultrafine particles (UFPs). PM2.5 are particulates measuring 2.5 micrometers in diameter or less, while UFPs are smaller than .1 micron in diameter.

PM2.5 and UFPs can be absorbed into the bloodstream once inhaled; from there, they can damage all organs in the body.

Pictured: Camp Nelson’s air quality measured hazardous level air quality at 388. The trailhead for the 100 Giants Trail at Long Meadow Grove is located at the southern end of the Windy Fire. Source: IQAir

Conditions ripe for extreme fire season

The 2021 western wildfire season has been busy due to hot, dry conditions, and those factors are making the KNP Complex Fire difficult to control. Timber litter, brush, chaparral, short grass, and old snags – dead or dying trees – are all fueling the complex fire.⁴ In addition, steep terrain is creating a challenge in accessing difficult to reach fires.

In recent years, human-induced climate change has spurred longer and more intense wildfire seasons. Climate change has resulted in record heat waves and an extensive drought, creating ideal conditions for wildfires in a wide geographic region stretching from British Columbia, to Northern California and from Minnesota to Colorado. Extreme heat in British Columbia, Washington State, and Oregon helped fuel incredibly destructive Northwest Pacific Coast fires in August.

Wildfire smoke from the western wildfires turned the skies over the East Coast vibrant colors as airborne pollutants blanketed most of North America in July 2021.

Other California fires

The KNP Complex Fire isn’t the only blaze firefighters are contending with in California. There are nine other major fires left to extinguish, at varying levels of containment.⁵ Most are in Northern California.

As of September 20, the Caldor Fire is 72 percent contained. The fire had threatened South Lake Tahoe in early September. That danger has since passed, and tourists are returning to the community.⁶

The Dixie Fire, once the largest single source fire and the second largest fire of any kind in California history, is 90 percent contained. The fire has been burning since July 13.

Other northern California fires include:

• Tiltill Fire: 2,350 acres, 90% contained
• Antelope Fire: 145,632 acres, 88% contained
• Monument Fire: 218,457 acres, 53% contained
• River Complex: 195,779 acres, 50% contained
• McCash Complex: 84,471 acres, 22% contained

The French Fire, 28 miles from Bakersfield in Southern California, once ranged over 26,535 acres but is 98 percent contained.

In 2021, there have been 71 large fires reported in 12 states, scorching 3,219,092 acres in the United States alone. There have been 6,224 total fires in Canada as of September 15, burning 10,329,000 acres.⁷ Major fires have also been reported during the 2021 wildfire season in Greece, Turkey, Italy, and Siberia.⁸

The takeaway

Hazardous air quality is a danger to human health – but so is any measurement of air pollution. When air quality is poor, there are ways to take back control over one’s breathing space:

• Use an air quality monitor to uncover air pollutants in your community.
• Shut doors and windows to prevent wildfire smoke from affecting indoor air quality.
• Use an air purifier for wildfire smoke to keep airborne pollutants out of your home, office, school, or car.
• If you must go outdoors, put on an air pollution mask.