A Single Fire Killed Thousands Of Sequoias. Scientists Are Racing To Save The Rest

The world's largest trees are adapted to wildfires. But with fires getting more extreme, scientists warn that giant sequoias are running out of time.

Transcript

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California's wildfires are threatening some of the biggest trees in the world. The giant trees in Sequoia National Park can live for more than 3,000 years. But last year, a fire killed more than 10% of all of the sequoias. Scientists are now desperately trying to protect the others. Here's NPR's Lauren Sommer.

LAUREN SOMMER, BYLINE: It's not easy to kill a giant sequoia. The trees are among the largest living things on the planet.

ALEXIS BERNAL: That is what we would call a real giant sequoia monarch.

SOMMER: Alexis Bernal is standing next to that monarch, the name given to the oldest sequoias. She's a research assistant at UC Berkeley.

BERNAL: It's massive. Jenny, what was the diameter on this tree?

SOMMER: The trunk is 40 feet around. But it's pitch-black, scorched all the way to the top.

BERNAL: It's a hundred percent dead. There's no living foliage on it at all. Within just a hundred meters of us, I can see one, two, three, four, five, six, you know, seven, eight, you know, giant sequoia monarchs. And they're all dead.

SOMMER: Last year, the Castle Fire tore through these sequoia groves. It killed thousands of trees, as much as 14% of the entire population based on early estimates.

BERNAL: It's hard to see these trees that have lived hundreds to potentially thousands of years just die because it's just not a normal thing for them.

SOMMER: Not normal because sequoias can handle fire. Their bark is a foot thick. They tower over the rest of the forest without any low branches that might ignite.

SCOTT STEPHENS: These trees have been here 1,500 hundred years. So how many fires have they maybe withstood? Eighty?

SOMMER: Scott Stephens is a fire scientist at UC Berkeley. He says low-grade fires used to happen in these forests regularly, either from lightning strikes or used by Native American tribes to cultivate the land. But for the last century, fires were extinguished. The forests got a lot denser. And in a hotter climate, that's fueling extreme fires, the kind that can kill these giants. The research team is here to inventory the damage. But they're also looking for signs of hope.

STEPHENS: Two tiny sequoias here growing from a regeneration from the fire.

SOMMER: In the ashy dirt, Stephens finds tiny, green sprouts just an inch tall. Sequoias only release their seeds during a fire. The heat is what opens the cones. But the whole day we're there, the team only finds a dozen seedlings. They'd normally expect to see hundreds or thousands.

STEPHENS: Unless we see some regeneration of some of these sites, my goodness, you're not going to see sequoia here.

SOMMER: Climate change set the stage for the Castle Fire, says Nate Stephenson, who studied sequoias for decades as a scientist with the U.S. Geological Survey. Temperatures are rising. And in 2012, a drought hit. That turned the pine trees around the sequoias into kindling.

NATE STEPHENSON: The extra warmth that came with the drought pushed it into a whole new terrain. And that's what really helped kill a lot of trees. And they become fuel for fires.

SOMMER: This year, the sequoia seedlings that did sprout are contending with another hot, dry summer. Stephenson says most will not survive.

STEPHENSON: You have to wonder, well, what is going to happen there if we do nothing? There is talk maybe we need to go in there and plant trees seedlings to try to ensure that we get some trees back.

SOMMER: But the big question is, if you plant a tree that survives thousands of years, can it survive the climate it'll be living in then?

CHRISTY BRIGHAM: That is one of the gifts of giant sequoias - is that they force us to think in deep time. It forces us to confront the challenge of climate change.

SOMMER: Christy Brigham is head of resource management for Sequoia and Kings Canyon National Parks. She says planting new sequoias would be the backup plan. Right now, they're trying to protect the sequoias that are left. Her team, along with other federal agencies, are figuring out which groves are most at risk. Then they'll use controlled burns or other tools to make them more fire-resistant.

BRIGHAM: It is not too late. We can do better and - sorry. And people love these trees. So I just hope that we can take that love and translate it into immediate action.

SOMMER: Because the worst-case scenario is a Sequoia National Park with no sequoias. Lauren Sommer, NPR News. Transcript provided by NPR, Copyright NPR.