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The science and work that went before the fire: Fuel treatments can reduce fire intensity

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  • 5 min to read

Even when there are no wildfires to fight, fire personnel and land managers are working to mitigate future ignitions by rearranging or removing the fuels that feed them—trees and shrubs in both wild and developed areas. Called “fuel treatments,” crews usually undertake these projects in the off-season, and they can play a key role in fighting future fires. Fuels treatments in the area of the Pack Creek Fire gave firefighters safe places to work from and strategic areas to anchor their attack on the fire.

Land managers often plan fuel treatments in wildland areas adjacent to human developments to provide a buffer between that infrastructure and dense, fire-prone vegetation. That might mean sending crews into an area to thin out brush or trees with saws. Often those fuels are piled and burned in a controlled fashion during windows of ideal weather conditions. Another approach is chipping up trees with a mulching machine or masticator (often called a bull hog, after a brand name). During conditions likely to allow for a low-intensity burn, prescribed fire is a useful tool to reduce fuel loads.

Treatments like these help mimic the effects of fire in a natural cycle. For decades, land management agencies employed a “full suppression” strategy on all fires, which has resulted in a dangerous build-up of fuels in many areas.

“We've done a great job excluding fire from the landscape over the past hundred years, but now we're feeling the repercussions of that, because we actually need to have fire on the landscape,” said Jason Kirks, the fuels program manager for the Bureau of Land Management in Moab . “But we can't, because we have infrastructure—we have homes, we have roads… so we just can't let wildfire go where it used to go.” With fuel treatment strategies, land managers can achieve many of the benefits natural fires provide, while eliminating or minimizing the risks associated with wildfire.

In a report from the BLM, the Forest Service, and the Utah Division of Forestry, Fire and State Lands, (Interagency Pack Creek Wildfire/Fuels Treatment Interaction Success Report) officials analyzed how fuel treatments in the Pack Creek area affected fire behavior. It says that land managers have treated 1,555 acres of Forest Service lands surrounding the Pack Creek subdivision, using mastication; thinning, piling and burning; and prescribed fire. The BLM also treated 260 acres of fuels in that area, following the treatments with reseeding of desired plants.

Kirks, who is a qualified firefighter and provided leadership during the first day of the Pack Creek Fire, said those thinning projects, some of which had been conducted over a decade ago, were effective in slowing down the fire and moderating its behavior. Without those treatments, the fire would have traveled much faster and more intensely.

“The fuels treatments allowed us to take a tactical stand on the fire in these locations because the fuels were a lot thinner,” said Kirks. “Farther back where there was no fuel treatment, it was a full-on crown fire, with group torching,” he said, pointing to a map of the fire. “When it came through here it was just more of a smaller surface fire,” he said, indicating the location of the fuels treatment. He explained that fuels treatments are not meant to stop a fire, but rather to slow it down to allow firefighters to engage.

“Without the fuels treatments, several thousand more acres would likely have burned around Pack Creek,” according to the interagency report.

Fuels treatments may also be used to encourage the development of a desired ecosystem—for example, a vegetation type that historically has established itself in burned areas, but that has receded under full fire suppression management strategies. For the BLM fuel treatment projects near Pack Creek, the interagency report says the main objective was to “restore ecological health of the site and the restoration of a fire-adaptive ecosystem.” Crews thinned existing trees and cheatgrass and reseeded the land with native and non-native grasses and forbes.

Wildland/Urban Interface

The Pack Creek subdivision, which suffered damage and loss from the Pack Creek Fire, is an example of what fire managers call “Wildland/Urban Interface,” or WUI—a place where human-made infrastructure abuts natural fuels that can carry fire. In 2018, environmental scientists published an analysis of data showing that between 1990 and 2010, WUI area in the United States expanded by 33%, making it the fastest growing land use type in the lower 48, according to a summary of the research available on a United States Forest Service website.

The abstract of the research paper notes that WUI areas “pose the greatest risk to people due to the proximity of flammable vegetation,” and that structures are frequently burned in the WUI. Wildfires are most difficult to fight in the WUI, and the proximity of human activity to wildland areas means that wildfires ignited in the WUI are often human-caused.

Defensible space

It’s important, Kirks said, to consider and mitigate fire risks ahead of time in WUI areas. He explained some methods for mitigating fire risks and creating “defensible space” on private properties. For example, keeping trees cleared away from buildings.

“One juniper tree can put out flames 30 to 40 feet tall—just from one tree,” he said. If the wind is pushing those flames towards a structure and it’s located close by, there’s a high chance of ignition. However, ignition can also come from ember showers blowing from a fire that may be relatively distant from buildings.

“Those embers can land on roofs, they can land on rain gutters, they can land on piles of leaves, they're going to land on your landscaping—so all that stuff is now receptive fuel,” Kirks said. He advises property owners to keep their land clear of fuels, including raking up and disposing of leaves and pine needles. Bare ground, concrete, gravel, and metal roofs are all resistant to fire.

Even if not all mitigation strategies are practical for a property owner, at least implementing some of them can be helpful. Even removing one tree ahead of time could be crucial. Kirks said that just one mature juniper tree can weigh 2,000 pounds.

“We’re talking about 2,000 pounds of material that needs to be removed by human force,” he said. In an emergency, as when a fire threatens a property, there may not be time to safely and successfully undertake such an effort.

The interagency report mentioned above notes, “Years of thinning on private lands within the [Pack Creek] community by the Utah Division of Forestry, Fire and State Lands allowed fire resources [crews] to remain safely in the subdivision and save numerous structures.” Cleared areas provide safe ground from which to make a stand against the fire.

Pack Creek resident and former firefighter Scott Brown is quoted in the report describing how he regularly clears space around his home. “We have made several practices our routine, including keeping a 20 foot minimum ground vegetation barrier, trimming all annuals for 50 feet, limbing all nearby trees to 5 feet up, and chipping all dead woody fuel in that same radius,” Brown said. He cited the Colorado State Extension, Utah State Extension, and the Utah Department of Natural Resources as good sources of advice and information on defensible space, and said his family had taken advantage of a cost sharing program offered by the DNR for fuels reduction work.

“I am convinced that the advice we received, and our follow-through, saved our home during the Pack Creek Fire (that, and a bunch of incredible community dedicated firefighters from Grand County),” said Brown.

In an area like the Pack Creek subdivision, which abuts public land and expansive natural areas, property owners are likely keenly aware of their WUI status. However, any human-developed areas near natural fuel zones are considered WUI, including the Mill Creek and Pack Creek drainages in town and developments near the Scott and Norma Matheson Wetlands Preserve. Kirks explained that even though those areas feel urban, they can carry wildfire.

“There’s a lot of vegetation, a lot of brush, cottonwood trees—and even though it might be green and look really lush, all that vegetation that's been dying for years and years and accumulating, will carry a surface fire very rapidly,” warned Kirks. That proved true in the first days of the Pack Creek Fire, when intense fire defoliated and blackened cottonwood trees and willows in the riparian corridor that had been thick and green before the fire.

“I think a lot of times, people think they're safe in riparian zones because there's water. It looks nice. It's really green,” said Kirks. But in his experience, those lush areas can burn readily. Moab residents have seen that first-hand in the past and in recent years, in incidents like the Cinema Court Fire in 2018, which burned along Pack Creek in town and destroyed many structures, and several fires in the Scott and Norma Matheson Wetlands Preserve.

Land managers continue to monitor how fuel treatment areas regenerate and how they affect fire behavior. According to the interagency report, 87 intersections of wildfires with fuel treatments have been recorded since 2002 in the Canyon Country Fire Zone, which includes the Moab area. The fire management team that took over the Pack Creek Fire during its most intense and complex phase produced a storymap with more information on fuel treatments and fire behavior during the Pack Creek incident. It can be viewed at https://bit.ly/2SBAuGD