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U of I research provides guidance on fuel breaks

By John O’Connell

University of Idaho

MOSCOW, Idaho – An ongoing University of Idaho study should help officials with the federal Bureau of Land Management’s Twin Falls District Office better understand how and where to build fuel breaks for controlling wildfires.

Tim Prather, a professor in the Department of Plant Sciences within the College of Agricultural and Life Sciences and senior associate director of the U of I Rangeland Center, and Eva Strand, associate professor of rangeland ecology and management with the College of Natural Resources, are leading the research.  

Fuel breaks comprise fire-resistant vegetation, enabling the BLM and rural fire protection associations to get a foothold toward controlling the spread of wildfires.

The research team has been evaluating the species composition and effectiveness of 120 miles of linear fuel breaks adjacent to gravel roads throughout BLM land within the Magic Valley. They’re paying especially close attention to the role cattle grazing plays in maintaining viable fuel breaks.  

“The big issue here is the fires are going to do a number of different things,” Prather said. “They continue to degrade the sagebrush steppe, so that has a conservation impact in that we see less area available for several different animals in the environment. In that the fires are impacting the ability of ranchers to utilize those areas, that’s a significant economic hit as well.” 

Erik Kriwox, fire ecologist with the BLM’s Jarbidge Field Office, and other BLM officials collaborated with the researchers in selecting which fuel breaks to study.

The research data will also help inform planning of about 80 linear miles of additional fuel breaks scheduled for construction within Kriwox’s territory.

“It was really good coordination on U of I’s part to loop us in so we could make those recommendations of if you’re going to do this research here’s where we would like you to do it that would be the most valuable to us,” Kriwox said. “Even questions like orientations were questions that I had. Should we be focusing fuel breaks on north-south roads because the fires usually burn east to west or west to east?”

The three-year project started in October 2021. Kayla Johnston, a Ph.D. student studying forestry, range and fire sciences in CNR, has wrapped up her field work assessing 45 locations within fuel breaks south of Shoshone and in the desert between Twin Falls and Mountain Home.

She gathered data from two designated plots at each location – one within the fuel break and one nearby.  

Near Shoshone, fuel breaks have been fenced off 800 meters wide and up to 400 meters off the roadway, accommodating targeted grazing of cheatgrass as a fire-management tool.

Within the desert, Johnston is evaluating fuel breaks established in 2016 and 2017. She’s collected data on vegetation cover by species, fuel load and plant height within the fuel breaks.

Some of the species commonly planted within fuel breaks, such as forage kochia, are not native to the West but are chosen because they remain green throughout the season and don’t grow tall.  

“One question I’m asking is if the non-native species are spreading outside of the fuel break,” Johnston said. “In my 45 plots, I saw maybe one or two forage kochia plants outside of the fuel breaks, so not really.” 

She is also evaluating targeted grazing, grazing of fuel breaks included within pasture and no grazing for their effectiveness in fuel break maintenance.  

In 2021, when it was dry, Johnston found fuel breaks with native perennial grasses and forbs that were not grazed had excessive vegetation compared with the grazed pasture nearby. She’s concluded fuel breaks with native grasses should be mowed or grazed even in dry seasons.

In fuel breaks incorporated into pasture, cows attracted by lusher vegetation overgrazed certain spots, creating a situation in which highly combustible weeds could become established.  

“Grazing is a great way to reduce fuels, but it’s got to be applied to the landscape very mindfully,” Johnston said.  

Johnston plans to pore through fire records to determine if average wildfire sizes have shrunk over time where fuel breaks have been installed.

She’s participated in regular Zoom calls with officials from the BLM and landowners with rural fire protection associations to update them on her progress.  

“Fuel breaks are not meant to stop a fire. They’re meant to be another tool when firefighters are out there to stop a fire,” Johnston said. “When a fire breaks through one part of it, if there’s another fuel break not too far away firefighters can go and try to corral the fire next to it. Having a network of fuel breaks is really beneficial.” 

Katherine Lee, an associate professor of agricultural economics and rural sociology, is conducting an economic study assessing the costs and benefits of building and maintaining fuel breaks.

Part of Lee’s study will assess the value of forage for livestock grazing saved by fuel breaks versus the cost of creating and maintaining various types of fuel breaks.

“I think that would be a really key piece to see come out of that study, having something else to support putting funding into these projects — this is how much we’ve invested and this is how much it affects the permittees,” said Tony Erickson, supervisory fire management specialist with the BLM’s Twin Falls District.