Strategically placed buffers help slow the spread of wildfire 

California’s annual rangelands are famous for their green, rolling hills in winter and spring. But as the grass dries out, these landscapes become highly flammable and pose a significant fire risk. According to CAL FIRE’s Wildfire Activity Statistics Annual Reports, grass fires were the most common type of vegetation burned in the Central Sierra counties of El Dorado, Amador, Calaveras, and Tuolumne. From 2019 to 2023, they accounted for approximately 78% of all acres burned in the region, averaging about 3,033 acres annually (CAL FIRE, 2019–2023).

Mitigate wildfire risk by reducing fine fuels and adding fuel breaks

Reducing fine fuels is a critical proactive step in mitigating wildfire risk, especially in high-priority areas where grasslands border human activity. Fuel breaks are often most effective when placed near likely ignition sources, such as roads or powerlines, and around vulnerable assets like homes, communities, or critical infrastructure. In both cases, these strategically placed buffers help slow the spread of wildfire, improving the chances of containment and reducing the risk of catastrophic damage. Every year, fuel breaks are created and maintained by private landowners and livestock producers, county road and public works crews, local Fire Safe Councils, Resource Conservation Districts, CAL FIRE, private contractors, and others. 

Methods for creating and maintaining effective fuel breaks include targeted grazing

Common techniques include mowing, herbicide application, prescribed fire, grading, cultivating, and targeted grazing. Choosing the right method depends on many factors, including site conditions, ownership, ecological concerns, and available resources.

Targeted grazing can make a lot of sense on annual rangelands because it leverages livestock’s natural foraging behavior to turn fine fuels into marketable weight. This reduces labor for landowners and generates income for producers. Fuel breaks can protect ranchers from losing feed to fires that start along roads, and just as importantly, they help protect surrounding communities from fires that may start on the pasture. However, implementing fuel break grazing typically requires fixed or temporary infrastructure, often electric fences, parallel to the outer perimeter fence to concentrate grazing for the desired fuel reduction.

Virtual fencing as a flexible, labor-saving alternative to fenced fuel breaks

In June 2024, UCCE tested whether virtual fencing (VF) could provide a more flexible, labor-saving alternative to fenced fuel breaks by eliminating the need for an inner physical fence while still achieving comparable fuel reduction. The trial was conducted on a privately owned pasture adjacent to the city of Sutter Creek. After a productive growing season, the grass stood over 3 feet tall in many areas and averaged 4,269 pounds of dry forage per acre (the equivalent to about 71 bales of hay per acre, assuming 60 pounds per bale). Several homes stood within 50 feet of the fence line, making the fuel load a clear fire hazard. Removing such fuels could help achieve the 100’ of defensible space that CAL FIRE recommends.

Thirty-seven cattle of mixed age and breed with no prior exposure to VF were selected for this trial (Figure 1 Left). A single VF base station was placed near the trial site to allow the collars to properly communicate. After an 8 day training period, the herd was confined to a 150 foot wide grazing area between the outer hardwire perimeter fence and the VF boundary. The herd received salt and protein supplement during the trial to account for the decreasing forage quality of the dry grass. These were placed away from water and loafing spots to encourage more uniform utilization. Over 19 days, the herd grazed the 7.7 acre fuel break down to 780 pounds per acre (about 13 bales of hay per acre), an 82% reduction of flammable fuels (Figure 1 Right).

Figure 1. Left: Herd wearing VF collars. Right: Results of the fuel break grazing. The dashed line shows where grazing stopped along the VF boundary. 

The herd respected the VF boundary 99% of the time (Figure 2), being contained by the audio cues alone 81% of the time (Figure 3). Visually, the livestock appeared calm throughout the trial. The only water in the pasture were troughs placed inside the fuel break. As VF boundaries only prevent animals from leaving an area, the few cattle who did escape would eventually return voluntarily, drawn either by thirst, supplement, or the presence of the herd.

Figure 2. GPS locations (blue dots) of the herd during the 19-day trial. These points outline the location of the fuel break in relation to the city of Sutter Creek. 

Figure 3. Top: Percentage of audio and electric pulse cues received by the herd each day. The livestock learned to respond primarily to the audio cues alone as the trial proceeded. Bottom: Audio and electrical pulse count for the 37 member herd per day. Fuel Break 1 was the smallest and therefore required the most cues for containment. Given the herd size of 37 cows, ~600 cues per day equates to about 1 cue per animal every 1.5 hours.

Virtual Fencing offers extraordinary levels of flexibility compared to traditional fencing

Compared to physical fencing, VF offers extraordinary levels of flexibility to adapt grazing and exclusion areas to meet ongoing management needs. In this trial, a newly paved road crossed the fuel break, so we split the fuel break into two VF zones to exclude livestock from the road. The herd was easily moved to the second fuel break after grazing the first.

The primary tradeoff with using VF in this trial instead of electric fence was the width of the fuel break. While John Allen, the participating rancher in this trial, typically installs 60 foot wide fuel breaks using electric fencing, we chose a 150 foot wide VF to account for GPS inaccuracy and to reduce stress on the animals from excess audio and electric pulse cues. While this wider area provided a greater level of protection from wildfire, it also took approximately twice as long to graze to the same level of fuel reduction. 

“VF is quicker, easier, and more reliable than the electric fence we use nearby to graze a firebreak along the roadway. Also, it’s probably better suited to cows rather than calves that are going to the market,” says rancher John Allen.

Trial suggests Virtual Fencing may be an effective way to create linear fuel breaks in rangelands

This trial suggests that VF is an effective solution to install linear fuel breaks in fire prone rangelands, and it will likely gain value as the technology continues to mature. This application seems most practical as an added benefit for ranchers and land managers who have invested in VF to improve other areas of their operation, such as monitoring and managing livestock across vast or difficult-to-fence areas, as is common in many summer ranges. In this scenario, VF collars could be deployed slightly earlier in the season to schedule fuel break installation in critical areas just before cattle are moved to summer pasture.

Want to learn more?
Reach out to Brian Allen at brallen@ucanr.edu

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This work was funded by the USDA Natural Resources Conservation Service.

References
1) California Department of Forestry and Fire Protection (CAL FIRE). (2019–2023). Wildfire Activity Statistics Annual Reports. https://www.fire.ca.gov/our-impact/statistics