Photo: George Wuerthner.

I frequently read anecdotes and even research suggesting that “active forest management” can successfully slow or stop wildfires. In my experience, many of these claims ignore the role of changing weather conditions in fire control. For instance, despite the efforts of over 10,000 firefighters, the 1988 Yellowstone fire was only extinguished by snowfall on September 11, which finally enabled control of the fire.

The Milli Fire on Oregon’s Deschutes National Forest is a more recent example of how changing weather led to false claims that active forest management “saved” the community of Sisters, Oregon, from the wildfire.

In 2017, the Milli Fire charred approximately 24,000 acres. It burned within 4 miles of Sisters, Oregon, where proponents of active forest management, including the Deschutes Collaborative and Forest Service, claim fuel reductions slowed the fire’s advance and “saved” the community.

Local politicians, county commissioners, and even Oregon Senator Merkley now refer to the Milli Fire to justify increased federal spending on fuel-reduction projects.

But, like so much happy talk from agencies and other organizations, there is more nuance to the explanation than is readily admitted. The details tell a different story from the one promoted by fuel reduction advocates.

A bit of history. A lightning strike on August 11, 2017, within the Three Sisters Wilderness near Black Crater Lake ignited the flames. The fire took a month to contain fully, and at its peak, 675 firefighters were engaged in suppressing the blaze.

Area where “salvage” or post-fire logging occurred after the 2012 Pole Creek Fire. The Milli Fire burned through this same area just five years later. Despite the fuel reduction of two previous fires, including the Pole Creek Blaze, the wind-driven Milli Fire pushed through this area. Photo by George Wuerthner

By August 18, the Milli Fire was burning through the pathway of two previous fires—the Black Crater and Pole Creek blazes. According to the incident reports, “high winds and hot dry weather” made containment difficult.

Keep in mind that by this time, the Milli Fire was under active suppression efforts, with hundreds of firefighters, bulldozers, air tankers, and helicopters working to contain it. Crews cleared heavy fuels along the fire line using bulldozers and other heavy equipment while ground crews continue to burnout areas within the fire line to strengthen containment.

The August 18th Incident report provides details: “Abundant sunshine will lead to another warm and dry day across the fire on Friday. Highs are forecast to climb into the 70s and 80s, with relative humidity lowering to the teens and 20s. Winds are forecast to increase with gust potential from the west at 25 mph or greater. The Haines index will remain a 5 due to the dry and unstable conditions.” Red flag conditions prevailed.

The extreme weather conditions persisted into the next day, August 19. As the Central Oregon Dispatch Fire Information for August 19 reported, “strong winds caused the fire to spot across the containment line this afternoon, pushing the fire 2-3 miles east and southeast towards subdivisions on the edge of the city of Sisters.”

This is a complicated graphic, but the different colors represent the daily advancement of the Milli Fire. The long green segment shows how the fire initially grew eastward towards Sisters. The orange, yellows, and red are areas burned after the wind shifted blowing the blaze back up to the Cascades.

By August 20, the weather began to change, and cooler temperatures and higher humidity slowed the fire. However, as during the previous day, the Incident Report declared that “Weather is expected to continue to be a challenge, with the possibility of wind-driven embers igniting spot fires ahead of the main fire.”

By August 21, the blaze had grown to 10,496 acres, with 644 firefighters on scene. However, that evening of August 21, the Incident Report noted a shift in wind direction from the Southeast, which pushed the fire back west and north into the Three Sisters Wilderness away from Sisters.

This graphic shows (in gray) areas that were “commercially thinned” prior to the fire. Note that the thinning did not stop the fire, and overall, the tree mortality was of “mixed” severity, like much of the thinned forest.

By September 8, rain and the fact that the fire was burning through lava flows helped slow the fire’s advance, aided firefighters in containing the blaze, and led to a reduction in the number of firefighters to 59.

How to interpret the fire’s progress. First, note that the Milli Fire initially burned through two previous blazes. Both of these fires resulted in a “fuel reduction,” which apparently did not slow the blaze. The Milli Fire also burned through recent “hazardous fuel reductions,” meaning past thinning projects. Again, with no effect on the fire’s progress.

During these early days of the fire, the weather, dominated by hot, dry conditions (low humidity) and gusty winds, drove the blaze towards Sisters, Oregon.

Then, as reported above, by August 19, the fire was approaching Sisters, driven by winds. However, on August 20, the weather began to change. Cooler temperatures and higher humidity, combined with reduced wind, slowed the fire’s progress. Without high winds, the fire dropped to the ground. And this, when the Forest Service and Deschutes Collaborative assert, miraculously, that a prescribed burn slowed and halted the fire’s progress towards Sisters.

By August 21, the change in weather (and wind) was driving the fire westward and upslope into the higher elevations and lava fields of the Three Sisters Wilderness. This change in the wind and rain on September 8 finally allowed the Forest Service to contain the fire.

Apparently, it does not occur to the people promoting the Milli Fire as an example of how “fuel reductions” saved Sisters that perhaps the change in weather, particularly wind direction, had more to do with “saving” Sisters than the prescribed burn. After all, if two previous fires, hazardous fuel reductions, and a massive firefighting effort could not slow the fire, maybe something else—like a change in wind direction—was responsible for extinguishing the blaze.

The influence of wind on fire spread is not linear but exponential. A 20-mile-per-hour wind will spread a fire more than twice as much as a 15-mile-per-hour gust.

Keep in mind that wind negates fuel reductions. Wind-driven wildfires regularly blow embers miles ahead of the fire front, and easily go over, around, and through thinning projects, previous burns, and natural barriers.

For example, embers from the Eagle Fire that charred the Columbia Gorge were blown across the mile-wide Columbia River to ignite blazes on the Washington side of the waterway. If a mile-wide area without a stitch of fuel can’t stop a wind-driven fire, it’s delusional to think traditional fuel reductions will be effective under extreme weather conditions.

Looking from the Washington side of the Columbia River south to the Oregon side. The gray areas are forests charred by the Eagle Creek Fire, which jumped the Columbia River to ignite blazes on the Washington side. If the mile-wide Columbia River with zero fuel can’t stop a wind-driven fire. How delusional is it to suggest a little bit of prescribed burning or forest thinning can prevent a blaze under extreme weather conditions? Photo by George Wuerthner

Nevertheless, like so many wildfires, the Forest Service was quick to take credit for suppressing the blaze and celebrated its efforts. Watch this video that applauds the firefighters.

Notice how in several segments of the video, the wind is blowing hard. A couple of photos showing the smoke path being pushed across the horizon from the mountains towards the East (and Sisters. These images are one indication that wind was a significant factor in fire spread.

The Milli Fire eventually charred 24,000 acres, but some of that acreage resulted from back burns set to remove fuel from an advancing fire.

Advocates of active management suggest that forests east of the Cascades were historically open and park-like, and that, due to the alleged success of fire suppression, they are now “unhealthy” and naturally prone to extreme wildfires. However, other interpretations find that forests were more diverse and often naturally dense. They neglected to mention that most of the heavy growth at higher elevations was lodgepole pine, which tends to form impenetrable tangles. Lodgepole pine also tends to burn at high severity with long intervals between blazes.

I can’t definitively say the prescribed burn near Sisters didn’t help firefighters stop the blaze from advancing toward the community. Still, I suggest a much better explanation is likely that changing weather conditions, and thus Nature, did a great job of reversing the fire’s advance and “saved Sisters.”

The Forest Service is desperate to prove that its logging and burning fuel reduction program is effective, so it tends to ignore how much weather ultimately determines fire severity and spread. A far more efficient focus should be on reducing the flammability of communities.

As Forest Service researcher Jack Cohan has declared: “We’re spending huge amounts of money and not being very effective. In the wildfire world, we have this control attitude that’s dominated by people obsessed with a failed approach of control. We’re trying to control what we can’t control, and can’t be bothered to focus on what we can control. We will never be able to scale up wildfire policy for fire-adapted ecosystems as long as we have vulnerable communities.”

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