Grazing Fuel Breaks In The Wildland Urban Interface

Managing fuel loads is a significant challenge in California’s Wildland-Urban Interface (WUI), where urban areas are most at risk from devastating wildfires. A fuel break is a managed area where vegetation is reduced to create a gap that slows or halts the spread of wildfires. Electric fencing is often employed on annual grasslands to guide livestock along pasture edges, reducing grass levels to the point where a fire cannot cross that boundary. Previous research demonstrated that grazing to approximately 500 pounds of forage per acre will successfully halt the spread of fire across annual rangeland (citation). Virtual fencing (VF) offers a modern approach to implementing these critical fuel breaks without the need for the interior electric fence. 

In June 2024, we used Gallagher eShepherd collars on a herd of 37 mixed-age cattle to test the efficacy of VF in containing livestock along a narrow (120-foot-wide) fuel strip on a supplemental diet of trace mineral salt and protein lick. The trial took place on an annual grassland pasture in the Sierra Nevada foothills, adjacent to the city limits of Sutter Creek, CA. The Sutter Creek Fire Protection District requires property owners within the district to create a 12-foot fuel break around their properties. The 2024 spring in the Sierra foothills was exceptionally productive for forage production, ranging from 2,000 to 8,000 pounds per acre, but the time allotted for this trial was insufficient to graze the pasture to the desired levels. Over 24 days, livestock reduced the available forage from 4,296 pounds per acre to 790 pounds per acre, a reduction of 81% of the total available forage.

During this trial, the collars successfully contained the entire herd within the very narrow fuel breaks 99% of the time. While a few cattle strayed beyond the VF during the trial, the pasture's only water source was within the VF area, prompting them to return when thirsty and remain contained. The VF functions like a one-way gate, allowing cattle to leave but allowing them back without penalty. Notably, one cow lost her collar due to it being too loose. Using the mobile app, we were easily able to recover the collar in the field. Despite no longer wearing a collar, the cow mostly stayed within the intended area, likely influenced by the rest of the herd and the proximity of the water source.