A line of firefighters traversed the steep ridges near Blewett Pass last week. They resembled the green and yellow clad crews that poured into Kittitas County to battle raging wildfires last summer, but they ventured into the woods with a much different mission.
The U.S. Forest Service fire crews working in the Blue Creek area of the Okanogan-Wenatchee National Forest near Mineral Springs came to set fires rather than extinguish them. Shortly after they set out from a convoy of fire engines, underbrush in the area was aglow with flames.
The intentionally-set fires, called prescribed burns, might seem invasive and smoky at first glance.
But officials say they help return the forest ecosystem to a natural balance and prevent more destructive, high-intensity wildfires that send larger amounts of smoke into the sky.
Kimiko Nale, fuels technician for the Cle Elum Ranger District, hopes to burn 1,600 acres of the district in the same manner this year, but officials say they’re “barely putting a dent” in the amount of forest that needs work to return to a natural, more fire-resistant state.
“What we try to do with our prescribed fire and a lot of our thinning is to restore the forest to what is natural,” Nale said.
In the last 100 years, Nale says population growth in the western United States has resulted in larger numbers of people living in or near forested areas. That has spurred the suppression of more wildfires burning across the West in an effort to protect people and property.
“A lot of fires we have to suppress because they are threatening life or human property, but there’s a trade off to that,” Nale said.
Low-intensity fire plays a natural role in forests, Nale says. It helps to clean out the forest floor, removing smaller or unhealthy trees, so remaining trees have less competition for sunlight and water and can grow up healthy. Some trees need low-intensity fire to open their cones and spread seeds. Fire also returns nutrients to the soil and creates gaps in the trees, which provide wildlife with more space to roam and the ability to spot predators more easily.
“That’s what prescribed fire is trying to do, is sort of mimic those historic fires,” Nale said.
Prescribed burns are just one of a number of tools, including thinning and logging operations, used to restore forests to their natural state. Forest restoration tools work together, Nale said, and an area will typically be thinned, a process which removes brush and smaller trees, before it is burned to ensure a lower intensity fire. Prescribed burns sometimes aim to eliminate flammable debris leftover from logging and thinning.
Overgrown vegetation can make forests more susceptible to tree-killing insects and disease and weaken or even kill trees.
In addition, intense fire, seen in many wildfires that burn through unnaturally overgrown areas, can sterilize soils and destroy wildlife habitat.
“I think that’s one of the biggest problems we have in the forest, is overpopulation of trees,” Nale said.
Forest Service restoration projects attempt to return a natural balance of tree species to the area, which historically had more pine species and fewer firs than today.
Fire danger increases in areas overpopulated with trees and underbrush or filled with weak or dead trees.
In September 2012, a lightning storm rolled across Central Washington sparking more than 100 small fires, some of which would later grow to become the 66-square-mile Table Mountain Fire in Kittitas County and the 88-square-mile Wenatchee Complex Fire in Chelan County. Both fires burned through the fall, consuming large swaths of the Okanogan-Wenatchee National Forest. But Nale believes Forest Service prescribed burns and other forest restoration tools helped slow or contain the fires’ spread in some places.
“I think it was very effective,” Nale said of the forest restoration efforts’ ability to protect communities and slow last summer’s fires.
Restored forest areas have less fuel to keep a fire burning or move flames into the forest’s tree-top canopy.
“Once fire gets into the canopy of those trees, it becomes a crown fire, which we’re almost unable to control,” Nale said.
Firefighters on the ground don’t work directly against crown fires because of the danger involved.
“We try to move back to the next ridge, where we can actually build a line and let that fire once it moves back down to the forest floor, burn to our line and contain it there,” Nale said.
To lessen the risk of a controlled burn becoming a wildfire, Nale says Forest Service crews keep plenty of fire engines and personnel in a burn area and only light prescribed burns under certain weather conditions. Nale considers variables like wind speed and direction, temperature, humidity and the amount of moisture in vegetation that might fuel a fire before lighting prescribed burns. She also runs models to predict what kinds of fire behavior might occur after crews light a burn, and that information helps determine what resources she might need to ensure crews stay in control of the blaze.
“There’s a lot of science that goes on prior to actually igniting the prescribed burn,” Nale said. “Before we light the match or anything, I make sure that we are within that prescription, so the fire can stay controlled.”
Prescribed burns typically happen in the spring or fall, but exact timing can depend on the specific project and its location. Nale said wind is the hardest factor to work with in Kittitas County when planning burns. High winds can throw embers from a fire onto dry fuels outside control lines, creating smaller spot fires. They can also spread smoke into populated areas.
“We let them know prior to burning so they can either stay away from the area or do whatever they need to protect themselves,” Nale said.