Now, even that shrunken sequoia forest is under threat. Wildfires have killed off nearly one-fifth of all large sequoias across their native range over the last decade; a steep loss for a species that can live for thousands of years.
A new study, published in the journal Forest Ecology and Management, finds those losses aren't inevitable. Researchers at the University of Nevada, Reno studied Mountain Home Demonstration State Forest, home to the world's largest old-growth sequoia grove, after the 2020 Castle Fire burned through the entire property. Some parts of the forest had been thinned or deliberately burned in the 15 years before the fire, while others hadn't.
The difference was stark. Sequoias in untreated forest died at more than double the rate of those in treated areas, said Bryant Nagelson, the study's lead author.
"Our survival rate was about twice as high as the survival rate in areas that had not received any kind of recent treatment within that 15-year window," he said.
Sarah Bisbing, a UNR forest ecologist and study co-author, said the strategy is essentially beating a wildfire to the punch.
"We have burned up the fuel ahead of a fire, so when a fire arrives, there is limited fuel to actually be able to burn on that landscape," she said.
Giant sequoias evolved alongside fire — their cones even need heat to release seed. But more than a century of fire suppression across the West has let fuel pile up in most groves, making today's fires burn hotter than the trees are built to withstand.
Bisbing said that the same imbalance exists in forests across the West, many of which are carrying decades of unburned fuel as the climate warms. That’s a mismatch that researchers say makes proactive treatment like prescribed burns and fuel-reduction increasingly urgent well beyond California's sequoia groves.
Both researchers pointed to the Great Basin bristlecone pine as another example of long-lived, narrow-range trees that could benefit from the same approach.
“For all remaining old-growth forests across the West, we’re talking about relatively small native ranges,” Nagelson said. “So, that is a point of optimism for me. That when we boil it down to a small area, we can really make a difference through prescribed fire.”
This story was produced by the Mountain West News Bureau, a collaboration between Boise State Public Radio, Wyoming Public Media, Nevada Public Radio, KUNR in Nevada, KUNC in Northern Colorado, KANW in New Mexico, Colorado Public Radio and KJZZ in Arizona as well as NPR, with support from affiliate newsrooms across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
