Taking a closer look at the impact of the SQF Complex Fire on the big trees
As we have noted before, the SQF Complex Fire (also known as the Castle Fire), has had a profound impact on the giant sequoia groves in the Sierra Nevada. As of mid-October, about 16,563 acres have burned in the giant sequoia range (roughly 34 percent of the range), most of which is old growth.
The larger issue is fire severity. Fire-resilient giant sequoia are likely to survive a low-to moderate-severity fire, which could really be largely restorative by reducing fuels and tree density. In contrast, high-severity fire that consumes nearly everything in its path is too hot for giant sequoia to survive. Although significant seedling regeneration may still occur—since the cones need heat to open—the ancient trees that are killed in this type of fire are irreplaceable. Using satellite data tracking images both pre-fire and post-fire, we were able to get preliminary figures for fire severity in the giant sequoia groves that burned in this fire. We will refine these numbers as the smoke in the area settles. Some areas burned at low to moderate fire severity (green and orange colors on the map), and in these areas the fire likely had some restorative effects. But, as shown in the map and outlined in the table, the preliminary fire severity data suggest that roughly 40% of the burned areas within the sequoia groves burned at high-severity, which means there will be potentially very large losses of ancient giant sequoia in this one fire.
Giant sequoia are not only fire resilient, they are fire dependent for their regeneration, but fire exclusion has dramatically reduced their fire resilience. Both Yosemite and Sequoia-Kings Canyon National Parks have restored several groves using prescribed fire and some mechanical thinning, but most of the groves in the range still need restoration to be fire resilient in the warming climate.
2020 has been a record fire year not only for California, but for its impacts on giant sequoia as well. With heavy fuel loads as a result of fire exclusion and the warming climate, severe fires that kill giant sequoia have dramatically increased in the last five years. According to CalFire data, roughly 25% of the range burned in wildfires between 1910-2015. In the last five years, 65% of the range has burned – 33% of it in 2020 alone. Although giant sequoia need fire, these groves were generally in a heavily fuel-loaded state prior to these recent fires, leading to high severity and loss of ancient monarchs.
These fires are raising an alarm bell. But even as this is a story of loss, I still feel hope for the sequoia, because we know what we need to do to ensure that these ancient giants persist on the landscape. We need to restore more “good fire” so that the ancient trees—the oldest of which had survived hundreds of wildfires prior to fire exclusion—survive into the future.