Yosemite's imperiled sequoias to be wrapped with fire-resistant foil

The largest grove of giant sequoias in Yosemite National Park was closed Friday and hundreds of people ordered evacuated nearby as a wildfire burning through dense forest became the latest in recent years to threaten the world’s largest trees.

A team was being sent to the Mariposa Grove to wrap some of the massive trunks in fire-resistant foil to protect them as the blaze burned out of control, said Nancy Phillipe, a Yosemite fire information spokesperson.

More than 500 mature sequoias were threatened but there were no reports of severe damage to any named trees, such as the 3,000-year-old Grizzly Giant.

The cause of the fire was under investigation and the rest of the park remained open as nearly 300 firefighters tried to control the flames with the help of two water-dropping helicopters and an air tanker dumping flame retardant, Phillipe said.

The giant sequoias, native in only about 70 groves spread along the western slope of California’s Sierra Nevada range, 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 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.

There was no obvious natural spark for the fire that broke out Thursday next to the park’s Washburn Trail, Phillipe said. Smoke was reported by visitors walking in the grove that reopened in 2018 after a $40 million renovation that took three years.

The grove, which is inside the park’s southern entrance, was evacuated and no one was injured.

The fire had grown to 466 acres (188 hectares) by Friday evening, authorities said.

Evacuation orders were issued Friday for the grove along with the nearby community of Wawona — which is surrounded by the park — and the Wawona Campground, where about 600 to 700 people were staying in a campground, cabins and an historic hotel.

A fierce windstorm ripped through the grove a year-and-a-half 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, but winds Friday were calm and the fire was not spreading rapidly.

The park has used prescribed burns to clear brush around the sequoias, which helps protect them if flames spread farther into the grove.

"When the unwanted fires hit those areas, it tends to slow the rate of spread and helps us gain some control," Phillipe said.

In the Sierra foothills, 80 miles (128 kilometers) to the northwest of the Yosemite fire, some evacuation orders were lifted as containment grew to 70% on the Electra Fire that had burned 7 square miles (18 square kilometers).

The fire broke out near Jackson on Monday and temporarily forced about 100 people celebrating the July 4th holiday along a river to seek shelter in a Pacific Gas & Electric Co. facility.