On a hot afternoon in California’s Sequoia National Park, Alexis Bernal squints up at the top of a 200-foot-tall tree.

“That is what we would call a real giant sequoia monarch,” she says. “It’s massive.”

At 40 feet in diameter, the tree easily meets the definition of a monarch, the name given to the largest sequoias. It’s likely more than 1,500 years old.

Still, that’s as old as this tree will get. The trunk is pitch black, the char reaching almost all the way to the top. Not a single green branch is visible.

“It’s 100% dead,” Bernal says. “There’s no living foliage on it all.”

The scorched carcasses of eight other giants surround this one in the Alder Creek grove. A fire science research assistant at UC Berkeley, Bernal is here with a team cataloguing the destruction.

It’s not easy to kill a giant sequoia. They can live more than 3,000 years and withstand repeated wildfires and droughts over the centuries.

Now, with humans changing both the climate and the landscape surrounding the trees, these giants face dangers they might not survive.

Last year, the Castle Fire burned through the Sierra Nevada, fueled by hot, dry conditions and overgrown forests. Based on early estimates, as many as 10,600 large sequoias were killed — up to 14% of the entire population.

“This is unprecedented to see so many of these large old-growth trees dead, and I think it’s a travesty,” says Scott Stephens, fire scientist at UC Berkeley, as he surveys the damage. “This is pure disaster.”

With extreme fires increasing on a hotter planet, scientists are urgently trying to save the sequoias that remain. Researchers from federal agencies and universities are teaming up to find the sequoia groves at highest risk. The hope is to make them more fire-resistant by reducing the dense, overgrown vegetation around them, before the next wildfire hits.

But one year later, the sequoia groves are again under threat. At the time of publication, wildfires burning in Sequoia National Park are within a mile of a grove with thousands of sequoias. Firefighters are battling to contain the blazes.

“It’s hard to see these trees that have lived hundreds to potentially thousands of years just die,” Bernal says, “because it’s just not a normal thing for them.”