All over the world, people are fascinated by the largest and oldest trees, and giant sequoias are no exception. Growing to immense sizes over thousands of years, these ancient trees seem immortal. But in just two years, we’ve lost 13-19 percent of mature giant sequoias over 4 feet in diameter, and scientists are concerned about the future of the species.
What’s killing sequoias?
Sequoias are adapted to frequent natural fire and depend on it to reproduce. In recent years a combination of unnatural fuel buildup from fire suppression practices combined with climate change-driven drought and rising temperatures have created conditions where wildfires burn larger and hotter, not only killing unprecedented numbers of sequoias but also severely limiting their ability to reproduce. Drought-stricken sequoias are now also vulnerable to bark beetle attacks. Scientists and land managers are working on learning more about sequoia mortality and taking action to protect this iconic species.
Sequoias by the Numbers
- Over 85% of all sequoia grove lands burned in wildfires between 2015 and 2021, compared to only about 25% in the previous century.
- In 2021, the KNP Complex and Windy fires burned 6,109 acres of sequoia grove area in 27 separate groves.
- Over 1,000 acres of sequoia grove area burned at high severity, where regeneration may be limited and sequoia seeds may burn in a fire or be washed away by fire-related erosion.
- Between 2,261 and 3,637 sequoias over four feet in diameter were killed by the KNP Complex and Windy fires or will die within the next 3-5 years. This represents 3-5% of the entire population of sequoias.
- 436 acres may be vulnerable to total sequoia loss, including 335 acres on NPS lands.
- In 2020, 10-14% of all sequoias were lost in the Castle Fire (also known as the SQF Complex Fire).
- From 2015 to 2017, the average mortality rate of sequoias was 84% in areas that burned at high severity. This includes both initial mortality, where sequoias are killed during a fire, and delayed mortality, where sequoias die up to five years after a fire because of the fire’s impacts.
- During a hotter drought in 2014, scientists observed unprecedented and extensive sequoia foliage dieback, and 33 giant sequoias died standing in areas not recently impacted by fire.
Threats to Giant Sequoias
Giant sequoias are known for their resistance to insects and disease and their fire-adapted life cycle. While mature giant sequoias did die from fire impacts, the hotter drought of 2012-2016 appears to have been a tipping point for giant sequoias and other Sierra Nevada mixed-conifer forests.
Digging Deeper on the Research
For researchers, analysts, reporters, and anyone looking to dive deep into some of the latest data on giant sequoias, we’ve gathered resources and partner links to help you navigate the landscape. If you are looking to share a resource or report with our coalition members, please get in touch!
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