Giant Sequoias

Giant sequoias have lived with fire for thousands of years. Their thick, spongy bark insulates most trees from heat injury, and the branches of large sequoias grow high enough to avoid the flames of most fires. Also, fire’s heat releases large numbers of seeds from cones, and seedlings take root in the open, sunny patches where fire clears away fuels and kills smaller trees. But starting in 2015, higher severity fires have killed unprecedented numbers of large sequoias.

The hotter drought of 2012-2016 was a tipping point for giant sequoias and other Sierra Nevada mixed-conifer forests. This article highlights the following impacts to giant sequoias: higher severity wildfires resulting in the death of thousands of large giant sequoias, bark beetles as a newly observed cause of death, and acute foliage dieback as a short-term response to drought. Responses to these changes require coordination with many partners and more public outreach.

Although some giant sequoia trees have stood for thousands of years and are adapted to withstand frequent low and mixed severity fires, preliminary estimates suggest that the 2020 Castle Fire killed between 31 to 42% of large sequoias within the Castle Fire footprint, or 10 to 14% of all large sequoias across the tree’s natural range in the Sierra Nevada. This translates to an estimated loss of 7,500 to 10,600 large sequoias. These estimates may change as we acquire new data.

The 2021 fire season included two large wildfires (both started by the same lightning storm in early September) that burned into a large number of giant sequoia groves. Given the impacts of the 2020 Castle Fire to sequoia groves, where losses were estimated at 10-14% of the entire Sierra Nevada population of sequoia trees over 4 feet in diameter, there is significant concern by sequoia managers and the public regarding the impacts of these new fires.

During 2020 and 2021, two major wildfires burned through twenty-eight different sequoia groves within Sequoia and Kings Canyon National Parks (SEKI). An estimate puts up to 14,000 sequoias, or 19%, of all large sequoias on earth killed in recent wildfires. Burned Area Rehabilitation (BAR) funding, in response to the 2020 Castle Fire and 2021 KNP Complex Fire, allowed park managers to begin planning for sequoia reforestation and work beyond.