Wednesday, April 17

With Yosemite’s giant sequoias at risk, firefighters place hope in prescribed burns | California

A wildfire has burned more than 2,720 acres in Yosemite national park, sparking global concern for the cherished groves of ancient and iconic tall trees clustered among the picturesque mountainsides. The fire, which was 22% contained Tuesday morning, also forced evacuations in the town of Wawona and caused the park to partially close to visitors. It’s possible that the blaze will smolder for weeks, even as containment increases.

As the Washburn fire crept closer to the Mariposa Grove, home to hundreds of giant sequoias, including the 3,000-year-old Grizzly Giant, which stretches over 200ft into the sky, firefighters installed protections for trees, setting up sprinkler systems to tame flames that might meet their bases with a bump of humidity and moisture.

But although these mitigations are effective tools against the onslaught of extreme fire intensity that has been a main culprit in killing swaths of sequoias in recent years, experts and officials are hopeful that work done well ahead of the wildfire will go even further to protect them. Prescribed burning and thinning treatments that remove dense and dried fuels from the forests may end up being instrumental in helping to reduce the worst effects.

In backburning operations, firefighters light smaller fires along containment lines that are easily managed, to remove fuel and stop a fire from spreading. Photograph: National Park Service

The blaze is big, and the rough terrain burning has made the perilous firefight, but it has not yet caused a calamity due to favorable weather and gentle winds. Officials are optimistic firefighters can corral the fire before a trifecta of dire conditions – devastatingly low humidity, rising temperatures, and strong gusts – send flames into a rage. Even with the added risks from a severe and record drought that’s left landscapes patched, there is still a good chance that this fire will do more good than harm.

“Recently there has been this association between fire and bad outcomes because the fires have been absurdly, apocalyptically intense,” said Daniel Swain, a climate scientist at the Institute of the Environment and Sustainability at the University of California, Los Angeles, noting that more ferocious fires in the west may erupt in the coming months. “This fire – so far – has not been a catastrophe.”

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Earlier prescribed burns may help protect the sequoias

California’s Mediterranean climate evolved with fire, and forested ecosystems rely on the renewal offered by a burn. Indigenous nations ignited cultural fires to cull overgrowth from the land and help clear space for new trees to thrive. But over the last century, white settlers instituted fire suppression as a practice. As the forests became more crowded, the climate crisis turned up the dial, creating a new kind of fire – one that threatened even the most resilient trees adapted for flames.

Fueled by a combination of poor land management and intensifying conditions, extreme fire intensity has devastated sequoia groves. Close to a fifth of the world’s sequoias they were killed in fires in the last two years alone.

“We have seen incredibly severe fires in these giant sequoia groves that have essentially incinerated the entire forest and turned the giant, ancient trees into matchsticks,” Swain said. But this fire has behaved differently due to timing early in the season and prescribed fire treatments and thinning – the removal of trees often required to ensure prescribed burns don’t escape control and become infernos.

Smoke over trees and a small shop
Smoky conditions in Yosemite national park. Photograph: National Park Service

The flames may move into areas that haven’t been treated, where there’s been a buildup of dense dead and downed trees that turn to kindling along the forest floor. But, aided by burn scars from recent blazes that reduced the load and conditions that are, so far, more favorable, Washburn could be a healthier fire, more like those that historically burned through this region.

“Right now we are fortunate to have relatively mild winds,” said Stanley Bercovitz, a public information officer with the interagency team managing the fire response. Temperatures are high, but have lingered beneath 100F, and relative humidity has not dropped into the single digits.

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Bercovitz added that, although the timing has been helpful, risks are still high and conditions are ever-changing. “Right now there are a lot of resources available but that could all turn around in three days – there could be two new huge fires and there would be no resources available.”

There’s always a chance that conditions will shift. If the flames creep into areas that are densely covered with desiccated vegetation, it could be caused by a more catastrophic burn. “We have stopped fires for the last 100 years – and we are paying the price,” Bercovitz said of the overgrown landscapes still ripe for ignition. “We have created a nightmare situation.”

The firefight has challenged crews working to contain the blaze, officials said Monday, but they emphasized that confidence remains high. Smoke has cloaked the surrounding areas, causing unhealthy air quality in places where throngs of tourists remain outside. There are also structures at risk, along with cherished spaces within the park.

“There are tremendous values ​​at risk in this fire,” Yosemite’s superintendent, Cicely Muldoon, said during a community meeting on Monday night, noting the town of Wawona and the Mariposa Grove, which she referred to as the “root of the whole national park system”. “I know these closures are super hard,” she added, but “the team has made some awesome progress.”

Although the risks are extremely high, the fire behavior has left many optimistic. There has been a change in perspective in how to dull fire risks that could help threatened areas navigate the growing intensity expected in the years ahead. Backed by climate scientists, ecologists and fire officials, prescribed burning and other treatments are more often deployed.

“We have learned a lot in the five decades since we started suppressing fire – the unintended consequences of fire suppression,” said Kelly Martin, former chief of fire and aviation management at Yosemite, who oversaw some of the treatments now protecting Mariposa Grove from an escalation in fire conditions. The work not only helped reduce risk, but also spurred sequoia regeneration, ensuring that seeds could better reach the soil.

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firefighter walks through woods with fire ahead of them
An early morning backburning operation near the south entrance of Yosemite. Photograph: National Park Service/EPA

“The problem is we didn’t recognize the dangers that were lurking outside the grove and the potential for large wildfires to hit these groves from the outside,” she said, noting that her team amended its suppression plans before her 2019 retirement. Those plans are already having an impact on crews working to contain the Washburn fire.

“Over the decades the park has been doing prescribed burns in the Mariposa Grove that now has protected the grove and allowed the firefighters a safer, more effective place to control this wildfire,” Martin said. “That’s what we are seeing play out now.”

Across the west more of this work is being done, but as conditions have grown more intense the window to perform them safely is shortening. There’s also a significant amount of catch-up that needs to be done, and most agencies are abysmally behind in treating the landscapes.

Plans that were in place have also been challenged by a small minority of environmentalists, who have raised concerns that thinning is just logging in disguise. Earlier this month, a federal judge halted tree thinning and removal projects in Yosemite after the Earth Institute, an environmental non-profit, filed a lawsuit against the park. The plan would have culled trees less than 20 inches in diameter that were dead and downed.

That’s one reason, Martin said, that, if this fire is able to achieve that desired mosaic on this landscape, leaving some patches unburned while opening parts of the thick forest canopy to biodiversity, it will have a positive impact.

“Nature has a way of understanding and doing this work that’s been going on for centuries,” she said. “When you see it on the landscape it is a sight to behold when it comes back the following year.”

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