Some of the oldest trees on Earth -- the giant sequoias -- are facing new challenges

LEILA FADEL, HOST:

Giant sequoias are survivors. They can live more than 3,000 years. But in a changing climate, the trees have become more vulnerable. NPR's Julie Depenbrock brings us this postcard from Sequoia National Park.

JULIE DEPENBROCK, BYLINE: On the day I visit the park, a drone flies overhead.

(SOUNDBITE OF DRONE)

DEPENBROCK: It's here to detect signs of stress in General Sherman, the world's largest tree. Clay Jordan is the superintendent of Sequoia National Park.

CLAY JORDAN: So they found a little bit of beetle activity in the canopy of the tree, but not anything to cause us great concern at this point.

DEPENBROCK: The beetle he's referring to is the sequoia bark beetle, which had coexisted peacefully with the trees.

JORDAN: Until just a few years ago, we didn't have a single instance where this beetle has killed a giant sequoia, and now we have a few dozen.

DEPENBROCK: Jordan says climate-change-driven drought has likely weakened the trees. The National Park Service, along with the U.S. Geological Survey, found in 2021 that warming temperatures mean more bark beetles and more vulnerable sequoias. But it's not the sequoias' only threat, says park ranger Tina Carpenter.

TINA CARPENTER: With the two most severe recent wildfires that we've had, between 2020 and 2021, we lost 13-19% of the giant sequoia species.

DEPENBROCK: Carpenter is giving a tour of the park.

CARPENTER: We're going to walk the trail up to the General Sherman tree.

DEPENBROCK: In 2021, as wildfire encroached, General Sherman was wrapped in fire-resistant material. The more-than-2,000-year-old tree was safe, but others were scorched. Carpenter points to two trees nearby.

CARPENTER: With these trees here, we can also see a fire scar, where the fire burned the bark back, exposing the wood beneath it, leaving this triangular-shaped scar.

DEPENBROCK: Giant sequoias need fire. It helps release seeds and create space for saplings to flourish. For more than a century, humans have been putting out wildfires. Now, they're trying to return it to the land in a controlled way.

CARPENTER: So when we prescribe fire to the landscape, we're actually trying to bring the health of the landscape back.

DEPENBROCK: But catastrophic fire, fueled by climate change, can overwhelm the trees. With wildfire season in sight, these threats are top of mind for the park.

CARPENTER: We're here to preserve and protect these places, so future generations also get to experience that, as well.

DEPENBROCK: Carpenter says the thousand-year-old sequoias that were lost to fire can't be recovered in this lifetime - but maybe the next.

Julie Depenbrock, NPR News, Sequoia National Park. Transcript provided by NPR, Copyright NPR.