Fire and Sequoias
Giant sequoias are adapted to periodic fire. Sequoia bark typically protects the trees against significant damage. At up to 24 inches thick and extremely fibrous, sequoia bark not only resists burning but also insulates the tree against fire’s heat.
Fire also prepares the bare, mineral soil required by sequoia seeds for germination. It burns off undergrowth and trees that compete for the abundant sunlight young sequoias require. The reproductive success of giant sequoias demands only that each tree produce one maturing offspring over its lifespan of several thousand years.
Scientists estimate that approximately 20 percent of the naturally occurring sequoias in the Sierra Nevada have burned in wildfires in the past two years alone. The sheer number of trees lost in such a short period is a disheartening and shocking development, particularly given that sequoias rely on fire to reproduce. But the sort of high-intensity wildfires that have wreaked havoc throughout the American West in recent years are like nothing the sequoias have ever experienced. Cedar Grove was the only area that did not experience fire in 2021.
“The fires these trees have evolved with are not the fires we see burning today,” says Garrett Dickman, a wildfire botanist with Yosemite National Park. “The fuels around these trees are drier and the fuel loads are way higher than these forests have ever seen before.”
“If you go through the old literature on giant sequoias, you cannot find a single instance of a tree being killed by an insect,” says Nathan Stephenson, a scientist emeritus with the U.S. Geological Survey and one of the foremost experts on sequoias. “It may have happened, but it was so rare that no one had ever seen it.”
It is happening now. Stephensen has counted dozens of old-growth trees in Sequoia National Park that have succumbed to the elements in the past decade—an occurrence he had seen only twice in his previous 35 years of observation.
The International Union for the Conservation of Nature has listed sequoias as endangered due to their dwindling numbers. The U.S. Endangered Species List has them categorized as threatened, and new consideration may be underway after the recent devastation that has forest scientists on high alert.
