Yosemite's giant sequoias will be all right, expert says

The Rim fire in and around the west side of Yosemite National Park jumped today to 160,980 charred acres, with new evacuations in areas outside the park. Firefighters were able to declare 20% containment, helped today by water drops from DC-10 tankers, diminished winds and some easier terrain. More than 3,750 fire personnel are on the Rim fire, according to the 8 p.m. update from the command post.

The fire has been racing through Sierra forest where the era of wildfire suppression has allowed the amount of fuel to build up. This fire is burning hotter and faster than any in modern Sierra Nevada history, according to the LA Times. "This is it. This is the big one," Yosemite Fire Chief Kelly Martin told the paper.

With the Rim fire racing through the forest on the western edge of Yosemite, concern has turned toward the park's two small stands of giant sequoia trees in that sector, the famed Tuolumne and Merced groves. The National Geographic talked to an expert from Cal State Humboldt who said to relax: the giant trees are well suited to withstand wild fires, even this one. From the story:

"These two groves are precious resources that the public is concerned about, and rightly so, because they are amazing," Stephen C. Sillett told National Geographic. Sillett is an ecologist with Humboldt State University who specializes in tall trees....But Sillett said placing sprinklers around the sequoias in Yosemite isn't really necessary. "The main thing they are doing with sprinklers is appeasing the public, who are worrying about how ugly the area will look when they visit later and that some trees are going to die," he said.

"The big trees are going to be fine," Sillett explained. "Smaller, weaker, non-giant sequoias will die, but it's not so much that they are protecting the trees."

Sillett said full-grown sequoias are adapted to survive even the hottest wildfires. They have fibrous, fire-resistant bark that can grow up to two feet thick. Although fires can damage the biggest trees, they usually don't kill them.

Giant sequoias are the world's largest single trees by volume. They reach an average height of 160 to 279 feet (50 to 85 meters) and average diameter of 20 to 26 feet (6 to 8 meters). Record trees have been identified at 311 feet (94.8 meters) and 56 feet (17 meters) in diameter. The oldest known giant sequoia is estimated at 3,500 years old.

The giant sequoias, the earth's biggest trees, are unique features of California's landscape. They are found only in about 70 groves along the western flank of the Sierra Nevada. The second largest tree on Earth, the President in Sequoia National Park, was photographed for National Geographic by Michael Nichols. Sillett appears in this video from the President. And really, if you can't appreciate the majesty of the giant sequoias, you are beyond hope.

From a story by David Quammen in the December 2012 issue of National Geographic:

Giant sequoias are gigantic because they are very, very old.

They are so old because they have survived all the threats that could have killed them. They’re too strong to be knocked over by wind. Their heartwood and bark are infused with tannic acids and other chemicals that protect against fungal rot. Wood-boring beetles hardly faze them. Their thick bark is flame resistant. Ground fires, in fact, are good for sequoia populations, burning away competitors, opening sequoia cones, allowing sequoia seedlings to get started amid the sunlight and nurturing ash. Lightning hurts the big adults but usually doesn’t kill them. So they grow older and bigger across the millennia.

Another factor that can end the lives of big trees, of course, is logging. Many giant sequoias fell to the ax during the late 19th and early 20th centuries. But the wood of the old giants was so brittle that trunks often shattered when they hit the ground, and what remained had little value as lumber. It went into shingles, fence posts, grape stakes, and other scrappy products. Given the difficulties of dealing with logs 20 feet thick, broken or unbroken, the trees were hardly worth cutting. Sequoia National Park was established in 1890, and automobile tourism soon showed that giant sequoias were worth more alive.

One thing to remember about them, as Steve Sillett explained to me during a conversation amid the trees, is that they withstand months of frigid conditions. Their preferred habitat is severely wintry, so they must be strong while frozen. Snow piles up around them; it weights their limbs while the temperature wobbles in the teens. They handle the weight and the cold with aplomb, as they handle so much else. “They’re a snow tree,” he said. “That’s their thing.”

The coast redwoods of Northern California grow taller in some cases, but do not contain as much mass as the giant sequoias.

Photo from the President in Sequoia National Park, National Geographic/Michael Nichols