Some of the world’s oldest trees at risk in Yosemite wildfire

A raging wildfire in Yosemite National Park is burning in an iconic grove that contains some of the biggest and oldest trees on Earth, marking the latest bout of extreme summer weather exacerbated by climate change.

The blaze in the Mariposa Grove threatens to torch more than 500 mature giant sequoias, the largest species of tree in the world, as the fire continues to creep north. The Washburn Fire at the southern edge of the park in California has ballooned to 2,340 acres late Monday after doubling in size over the weekend.

“There has been a lot of activity and a lot of work by firefighters to protect the trees,” said Nancy Phillipe, a Yosemite park ranger and fire information officer.

Firefighters working from aircraft and on the ground in tough terrain are racing to hem in the fire before it destroys the gigantic trees that have inspired generations of trekkers and have attracted tourists from around the world.

Workers have even gone as far as to place orange sprinklers around the base of the Grizzly Giant, one of the most iconic sequoias in Mariposa Grove. The humidity from the mist provides a measure of “preventive first aid” if the fire gets too close, according to ecologist Garrett Dickman. “We really don’t want to leave this one to chance,” Dickman said while standing at the foot of the tree in a recent video on Facebook.

So far, none of the grove’s named trees - including the 209-foot Grizzly Giant as well as the Bachelor and Three Graces - are damaged, according to Phillipe. The fire is 25% contained as of Monday evening. The cause of the fire is still under investigation, Phillipe said.

The gargantuans, which can live for thousands of years, grow only in about six dozen groves along a narrow band on the western slopes of the Sierra Nevada.

Normally, the giant sequoia not only can thrive amid low- to medium-intensity forest fires - it needs them to survive. Its fibrous, bronze-colored bark resists burns and insulates the interior against the heat of periodic fires. Its tiny, oatmeal-sized seeds can only successfully take root in soil left bare by a blaze.

But recent fires, fuelled with vegetation killed by blistering drought and built up over years of fire suppression, are testing the mettle of nature’s most massive trees.

“We’re getting catastrophic fires at a magnitude that we haven’t seen before,” said Joanna Nelson, director of science and conservation planning for the Save the Redwoods League. “We’ve seen a really big uptick in fire extents and intensity and damage in the giant sequoia in particular since 2015.”

A wildfire sparked by lightning came dangerously close last year to General Sherman - a tree that is the world’s largest by volume and older than the Colosseum in Rome - before firefighters wrapped fireproof blankets around it and other giants in California’s Sequoia National Park, to the southeast of Yosemite.

Other giant sequoias have not been as fortunate. In total, three fires over the past three years have killed up to 19% of the entire population. An early melting of the Sierra Nevada’s snowpack in May is only turbocharging dry conditions this year.

The current Washburn Fire in Yosemite is also at the doorstep of Wawona, a community of about 160 within the park that is home to campgrounds as well as the historic Wawona Hotel. Normally swollen with tourists in the summer, the area cleared out after a mandatory evacuation order Friday.

The fire is casting a smoky pall over much of California. The haze blotted out the vistas of popular destinations in Yosemite such as Half Dome and El Capitan. It has grown so big that the Bay Area, some 150 miles away, was choking under an air quality advisory Monday due to the smoke.

Past blazes may help halt the current one. Officials said the fire’s march will be slowed as it approaches the footprint of a 2017 conflagration.

“That’s okay with us because what we have seen in the past is, when unwanted fire gets into a footprint area, then it tends to slow,” said Phillipe, the Yosemite park ranger.

For now, she urged visitors still streaming into other parts of the park to be patient as the southern gate remains shut: “There’s a higher impact on those other entrance stations since this one is closed.”