Standing strong: Prescribed burns aid sequoias in surviving wildfire

Giant sequoias in Yosemite National Park have survived their first wildfire in more than a century because of intentional burning to remove undergrowth beneath the towering trees. Prescribed burns have proven to be effective methods to help prevent wildfires. 

First Look

A famed grove of giant sequoias in Yosemite National Park survived its first wildfire in more than a century, thanks to efforts to regularly burn the undergrowth beneath the towering trees, a forest ecologist who toured the site said Tuesday.

Small, intentionally lit fires over the past 50 years essentially stopped the fire in its tracks when it hit the Mariposa Grove and allowed firefighters to stand their ground and prevent flames from doing more than charring the thick bark on the world’s largest trees, Garrett Dickman said.

“We’ve been preparing for the Washburn Fire for decades,” said Mr. Dickman, who works for the park. “It really just died as soon as it hit the grove.”

The fire that started Thursday near the grove had burned 5 square miles Tuesday, but was 22% contained and moving away from the largest grove of sequoias in the park. Based on prevailing winds, it was unlikely to return to the grove.

The blaze started near a trail. Authorities said it wasn’t from lightning and wouldn’t comment on whether it was sparked accidentally, intentionally or through negligence.

Hundreds of visitors and residents were evacuated from the nearby community of Wawona on Friday and the grove and southern entrance of the park were closed. The rest of Yosemite remained open, though it has been blanketed in heavy smoke at times.

Some of the sequoias were charred by flames that reached 70 feet up their trunks, but Mr. Dickman said he surveyed the grove and did not think any of the trees would die. The Galen Clark tree, a large tree at the top of the grove named for the park’s first guardian, was one of the few named trees that burned.

“It got a little bit of heat,” Mr. Dickman said. “But from the pictures I’ve seen it, too, is gonna survive.”

The sequoias are adapted to fire – and rely on it to survive. But more than a century of aggressive fire suppression has left forests choked with dense vegetation and downed timber that has provided fuel for massive wildfires that have grown more intense during an ongoing drought and exacerbated by climate change.

So-called prescribed burns – most recently conducted in the grove in 2018 – mimic low intensity that help sequoias by clearing out downed branches, flammable needles, and smaller trees that could compete with them for light and water. The heat from fires also helps cones open up to spread their seeds.

While intentional burns have been conducted in sequoias since the 1960s, they are increasingly being seen as a necessity to save the massive trees. Once thought to be almost fire-proof, up to 20% of all giant sequoias – native only in the Sierra Nevada range – have been killed in the past five years during intense wildfires.

The Monitor reported on prescribed burns last May:

Wildfire is a growing scourge across the American landscape. In California and other Western states, a combination of prolonged drought and climate change have heightened the risk of uncontrollable and sometimes deadly fires. But it’s a problem in many other places. ...  Fire experts, land managers, government agencies, and even the public have increasingly embraced the idea that the best defense against wildfires is regular burning. They say low-intensity, carefully managed fires can thin overgrown forests and reduce the buildup of fuels like pine needles, dead grass, fallen trees, and thick brush that produce more intense and destructive fires.

Fighting fire with fire, however, is a risky endeavor and has occasionally gotten out of control.

In New Mexico, firefighters were working Tuesday to restore mountainsides turned to ash by the largest wildfire in the state’s recorded history that broke out in early April when prescribed burns by the U.S. Forest Service escaped containment following missteps and miscalculations.

The Santa Fe County Commission in an afternoon meeting blasted federal officials and unanimously passed a resolution calling on the Forest Service to conduct a more comprehensive environmental review as it looks to reduce the threat of wildfire in the mountains that border the capital city.

The Mariposa Grove, home to over 500 mature giants, and Yosemite Valley were protected by President Abraham Lincoln in 1864 – almost a decade before Yellowstone became the first national park in 1872 and decades before Yosemite was added to the system in 1890.

Mr. Dickman said the grove had not seen a wildfire in over 100 years. Several large blazes have come close in the past decade but they stopped before reaching the grove.

The current fire remains small by those standards and has not been driven by wind. But it is burning in a forest littered with dense stands of trees killed by bark beetles and drought, as well timber blown down in a powerful windstorm last year that also toppled more than two dozen sequoias.

The previous prescribed burns in the grove gave firefighters a chance to set up sprinklers to protect trees that have lived longer than 3,000 years and grow above 300 feet in height.

So far in 2022, over 35,000 wildfires have burned nearly 4.7 million acres in the United States, according to the National Interagency Fire Center, well above average for both wildfires and acres burned.

In Utah, smoke and ash emanating from a growing wildfire in rural Tooele County blew into Salt Lake City on Saturday. By Monday night, the Jacob City Fire had grown to 6.4 square miles, with 19% containment, officials said.

Elsewhere in Utah, firefighters contending with heavy winds battled the 15.9 square-mile Halfway Hill Fire in Filmore. Law enforcement on Saturday arrested four men who investigators said abandoned a campfire that ignited the blaze.

The story was reported by the Associated Press.