California heat builds as crews protect Yosemite sequoias

Smoke and flames rise as the forest burns at Yosemite National Park in California, United States on July 10, 2022. The fire is burning around the Mariposa Grove of Giant Sequoias. (Photo by Neal Waters/Anadolu Agency via Getty Images)

Neal Waters | Anadolu Agency | Getty Images

A heat wave was developing in California on Monday but winds were light as firefighters battled a wildfire that poses a threat to a grove of giant sequoias and a small community in Yosemite National Park.

The Washburn Fire on the western flank of the Sierra Nevada had scorched about 3.6 square miles by Monday morning, an increase of about 300 acres (121 hectares) overnight, according to an incident update.

The fire was a threat to more than 500 mature sequoias in the park's Mariposa Grove and the nearby community of Wawona, which has been evacuated.

The area in the southern portion of Yosemite was closed to visitors but the rest of the national park remained open.

Mariposa Grove and Yosemite Valley have been protected since President Abraham Lincoln signed legislation in 1864.

Visitors check out the view from the east end of the Wawona Tunnel into Yosemite Valley, showing three major landmarks, from the left, El Capitan, Half Dome and Bridalveil Fall, obscured by thick smoke in the area from the wildfire burning to the south in the Mariposa Grove of Giant Sequoias, at Yosemite National Park, California, U.S., July 9, 2022. 

U.s. National Park Service | Reuters

A sprinkler system was set up within the grove to maintain moisture, and there were no reports of severe damage to any named trees, including the 3,000-year-old Grizzly Giant.

"Fortunately, the Mariposa Grove has a long history of prescribed burning and studies have shown that these efforts reduce the impacts of high-severity unwanted fire," a National Park Service statement said.

A heat advisory was issued for the Central Valley sprawling below the Sierra while up in the fire area a high of 88 degrees (31 Celsius) was forecast for Wawona.

The giant sequoias, native in only about 70 groves spread along the western slope of the Sierra Nevada, were once considered impervious to flames but have become increasingly vulnerable as wildfires, fueled by a buildup of undergrowth from a century of fire suppression and the impact of drought exacerbated by climate change, have become more intense and destructive.

Lightning-sparked wildfires over the past two years have killed up to a fifth of the estimated 75,000 large sequoias, which are the biggest trees by volume and a major draw for tourists.

There was no obvious natural spark for the fire that broke out Thursday next to the park's Washburn Trail. Smoke was reported by visitors walking in the grove.

A fierce windstorm ripped through the grove more than a year ago and toppled 15 giant sequoias, along with countless other trees.

The downed trees, along with massive numbers of pines killed by bark beetles, provided ample fuel for the flames.

In Utah, smoke and ash emanating from a growing wildfire in rural Tooele County blew into Salt Lake City on Saturday. By Sunday afternoon, the Jacob City Fire had grown to 5.9 square miles (15.3 square km), with zero containment, officials said.

Elsewhere in Utah, firefighters contending with heavy winds battled the 12.4-square-mile (32.2-square-km) Halfway Hill Fire in Filmore. Law enforcement on Saturday arrested four men who investigators said abandoned a campfire that ignited the blaze.

So far in 2022, over 35,000 wildfires have burned nearly 4.7 million acres (1.9 million hectares) in the U.S., according to the National Interagency Fire Center, well above average for both wildfires and acres burned.