Firefighters put the blaze under control on Thursday, with flames heading toward the signature grove of ancient giant trees in Sequoia National Park.
Using firing operations to burn flammable vegetation and other substances, before wildfires hit the vast forest, firefighters use their nemesis as a tool to stop, slow, or redirect fire. is one of.
The strategy comes with considerable risk if conditions change. But it is regularly used to protect communities, homes or valuable resources that are now at risk from fire, including groves of about 2,000 giant sequoias, including the General Sherman Tree, which by volume. The world’s largest.
Here’s how it works:
it’s all about the fuel
Three things affect how fast and hot a fire is: landscape, with fire burning rapidly on steep slopes; Flames with weather, winds and dry conditions; and fuel, the amount of material that can burn.
The first two can’t be controlled, but there are ways to reduce fuel long before any fires start – or even as soon as one is approaching.
“Of all the things that affect the behavior of fires, fuel is really where we can take action,” said Maureen Kennedy, a professor of wildfire ecology at the University of Washington.
Historically, low- to moderate-severity fires every five to 30 years burned excess brush and wood before fatal fires in the early 20th century, which led to aggressive firefighting and a US Forest Service policy to prevent fires. All the fires were suppressed by 10 am the next day. informed of.
This led to thick forests of dead trees, fallen logs and high brush accumulated over the past century, and more widespread fires.
slow fire by setting fire
For centuries, Native Americans have used fire to thin forests.
Scheduled burns under favorable weather conditions can help mimic low-intensity fires of the past and burn excess fuel when they are not at risk of getting out of control. If the fire eventually burns down the area, it will likely do so at a lower intensity and with less damage.
The idea is similar during a wildfire. Fire chiefs attempt to take advantage of changing winds or changing landscape to ignite an area before a fire occurs, depriving it of fuel.
“They’re trying to achieve the same effect,” Kennedy said. “They’re trying to control the fire behavior. They’re trying to get the fuel out of the fire that’s burning so intensely.
Of course, their goal is to better contain and control fire and protect more valuable resources. “
light fire safely
All wildland firefighters learn about burnout operations in basic training, but planning and executing a firing operation requires a higher level of training.
“You need to know how to fight a fire before you start a fire,” said Paul Broyle, former chief of fire operations for the National Park Service.
Burning an area between the front of the fire and a projected point – such as a fire outbreak or the Giant Forest in Sequoia – would have required the right conditions and sufficient time to complete the burnout before the fire could reach the fire line constructed by firefighters. Is.
Often such operations are performed at night when fires subside or their progress slows down as the temperature cools and the humidity increases.
The convection of fire draws winds in from all directions, which may help. As the fire climbs up steep terrain, burnouts will sometimes set up on the other side of a ridge, so any embers will land in an area where dry grass and brush have already burned.
Firing operations require a crew that ensures that the fire does not spread in the wrong direction. This may also include bulldozers cutting the flames or air tankers dropping retardants to further slow the flames.
Broyles said they all have to work in sync.
“Unless you follow up with the personnel, air tankers don’t put out fire on their own,” he said. “It’s like an army. You can’t get your enemy out of Hell without ground troops.”
While burnouts are commonly used, they can backfire if the winds blow or are not lit enough.
“When you put more fires on the ground, there’s a risk,” said Sequoia National Park spokeswoman Rebecca Paterson. “It has the potential to create more problems than it solves.”
Broyles said that at times he did not start the burnout on time and had to evacuate firefighters.
“Fortunately, in my case, we were not harmed,” he said.
Small flames to protect the giant sequoia
Patterson said on Thursday firefighters were conducting burnout operations on an almost microscopic level in the vast forest, moving from tree to tree. Ground cover and organic debris known as dust near the trees were being set ablaze, allowing the flames to travel away from the tree to form a buffer.
General Sherman and other giant conifers were wrapped in aluminum blankets to protect them from the extreme heat.
The park was the first in the West to use fixed fire more than 50 years ago and regularly burns some of its trees to extract fuel. Patterson said it was a cause for optimism.
“Hopefully, the Giant Forest will emerge from this unheard of,” she said.