How to save an ancient, giant tree from a wildfire

More than a century ago, natural John Muir took President Theodore Roosevelt to camp beneath an ancient, gnarled tree in Yosemite National Park.
The tree, known as the Grizzly Giant, was more than 2,000 years old, stood more than 200 feet tall and spread branches that were several feet in diameter. Soon after, Roosevelt, who described the tree and its surrounding grove as a “temple,” extended federal protections for the park in the Sierra Nevada of California.
In the past several days, however, the Grizzly Giant has been threatened the Washburn fire, which has torn through more than 3,000 acres of brush and timber in the southern part of the national park, and prompted evacuation orders for the tour-driven community of Wawona, California.
“We have to go to the ends of the earth to protect this tree,” said Garrett Dickman, a forest ecolog with Yosemite National Park, who is helping to manage the efforts to protect the Mariposa Grove of Giant Sequoias, the largest and most popular of the park’s three clusters with more than 500 mature trees.
“The past couple years have been a real wake-up,” he added. “We never thought the giant sequoias would really burn.”
California’s giant sequoias have faced particularly fierce wildfires since 2015, the result of climate change and a lack of frequent fire over the prior century, according to the National Park Service. The imminent threat — which has now reached some of the state’s most exalted trees — has prompted scients and firefighters to take exceptional steps to save them.
To protect the Grizzly Giant, authorities have set up a sprinkler system that runs intermittently, pumping 15 to 20 gallons of water per minute at the base of the tree to increase humidity, Dickman said. They are clearing debris from the ground, he added, as well as chopping down smaller trees that could ignite the ancient sequoias.
In other recent fires, firefighters have swaddled the trees in a flame-retardant foil, pumped foam onto them and showered them in pink fire retardant. Dickman said he had also considered pointing mers into the air near at-risk trees to create a “wall of water.” In other instances, he said, arbors have climbed up the giant trees to check for embers or to lop off their burning limbs.
During last year’s Windy fire, which burned through more than 1,700 acres in the Giant Sequoia National Monument, smokejumpers — firefighters who usually leap into an active fire zone parachute — spent about two days making their way up a smoldering tree, he said.
It took some workshopping, Dickman added. “How do you climb a tree that’s on fire?”
The Mariposa Grove, scients say, is probably less at risk than some other giant sequoia groves, given the decades of prescribed burning the National Park Service that they hope has prepared it well to avoid the most serious consequences of a wildfire.
On Tuesday, the fire was 22% contained and moving north, said Stanley Bercovitz, a spokesperson for the U.S. Forest Service. More than 600 firefighters have been working to put out the blaze.
The fire has already burned slowly along parts of the grove’s floor. Scients and authorities say the priority is to ensure it does not reach the tree canopy. Sequoias can withstand some heat and scorching on their trunks, but flames that reach the crown can torch them, as if it were a giant matchstick.
Once a majority of a giant sequoia’s leaves are gone, it can lose its photosynthetic capacity and die, Nate Stephenson, a scient emeritus in forest ecology for the U.S. Geological Survey, said. Although giant sequoias need some fire to regenerate, Stephenson added, “the conditions that fires are burning under right now have changed.”
While wildfires occur throughout the West every year, scients see the influence of climate change in the extreme heat waves that have contributed to the intensity of fires this summer. A majority of Mariposa County is also in exceptional drought, the U.S. Drought Monitor’s highest ranking. Trees affected drought will compete for limited water, and the stress can help make them more susceptible to insect infestation.
In a 15-month period between 2020 and 2021, an estimated 13% to 19% of the world’s population of sequoia trees were killed or mortally wounded, according to a report the National Park Service. The number is especially staggering, scients say, given how few died in the preceding centuries.
“I’ve counted a lot of dead giant sequoias, and I don’t like it,” said Dickman, the forest ecolog, who spent last fall counting the trees felled the Windy fire. At the end of the day, Dickman would get into his car, put his head on his steering wheel and sob.
“It’s like counting dead people,” he added. “It clobbered me.”
On Tuesday morning, officials said that the mature giant sequoias of the Mariposa Grove had “so far avoided serious damage” from the fire, and that they were feeling confident they could save them.
The cause of the Washburn fire was under investigation, but it was most likely caused humans, Cicely Muldoon, superintendent for Yosemite National Park, said at a community meeting Monday evening.
“As you all know, there was no lightning on that day,” Muldoon said.