This fall's wildfires in Sequoia and Kings Canyon national parks and the adjacent Sequoia National Forest possibly killed nearly 4,000 mature giant sequoia trees/NPS file

Wildfires that seared Sequoia and Kings Canyon national parks and neighboring Sequoia National Forest this fall claimed between 3 percent and 5 percent of the world's giant sequoias, according to the National Park Service. In simple numbers, the losses fall between 2,261 and 3,637 mature sequoias with a diameter of at least four feet.

The losses came from the KNP Complex, which burned mostly within the two national parks, and the Windy Fire, which burned mostly on the Sequoia National Forest, the Park Service announced Friday.

The impact assessment comes from a report compiled by a Burned Area Emergency Response team and was drawn from analysis conducted by scientists from the Nature Conservancy and the National Park Service. These giant sequoia groves are located across lands administered by Sequoia and Kings Canyon national parks, Sequoia National Forest, Tule River Tribe, UC Berkeley, and Save the Redwoods League, all partners in the Giant Sequoia Lands Coalition, established earlier this year to collaborate on strategies to protect these threatened trees.

These 2021 losses are being quantified in the wake of 2020s highly destructive Castle Fire in the same region, which resulted in the mortality of 10-14 percent of the world’s native population of large giant sequoias. After such devastating losses last year, there has been significant concern about the impacts of the 2021 fires.

The latest estimates include 1,330 – 2,380 trees within the KNP Complex footprint and 931–1,257 trees within the Windy Fire footprint. In total, 27 giant sequoia groves fall fully or partially within the perimeters of the fires. These estimates were calculated by comparing pre- and post-fire satellite imagery classified by fire severity, aerial reconnaissance, and on-the-ground assessments where possible.

While giant sequoias require periodic low-to-moderate intensity fire to maintain healthy ecology, a history of fire suppression across the American West has resulted in denser forests with high levels of fuel loading. In combination with hotter droughts driven by climate change, these conditions have changed how wildfire burns in the southern Sierra Nevada, resulting in large areas of high severity fire effects and massive fire events.

“The sobering reality is that we have seen another huge loss within a finite population of these iconic trees that are irreplaceable in many lifetimes,” says Sequoia and Kings Canyon National Parks Superintendent Clay Jordan. “As we navigate the complex process of restoring access to the parks, we will continue to work diligently with our partners in the Giant Sequoia Lands Coalition to become ever-better stewards of these incredibly special places, despite the enormous challenges we face.”

Some key areas, such as the Giant Forest in Sequoia National Park, experienced reduced fire severity, due in large part to a history of prescribed burning. As this year’s wildfires approached sequoia groves, firefighters deployed new tactics that reduced losses to these trees from high severity fire. Many areas within the fire footprints burned at low to moderate severity, and some areas did not burn at all.