Iconic sagebrush ecosystems of the American West are increasingly at risk from an accelerated cycle of wildfire and annual grass invasion that destroys thousands of hectares of sagebrush annually and threatens sensitive wildlife species, such as greater sage-grouse. Thus, rangeland and wildlife managers are challenged with finding methods to effectively thwart this novel disturbance regime, and increasingly look toward networks of fuel breaks as management tools. Fuel breaks may minimize catastrophic losses of sagebrush by reducing hazardous fuel loads, disrupting fuel continuity, and facilitating staging of initial attack and suppression operations, but an extensive evaluation of effectiveness at broad spatiotemporal scales is lacking. To fill this need, we conducted a retrospective analysis to assess biotic and abiotic factors influencing the effectiveness of fuel breaks at halting or altering wildfire spread across the Great Basin of North America (an area of 54,172,709 ha). We leveraged over 30 years of spatially explicit data describing annual wildfire events coupled with extensive geodatabases describing fuel break placement to construct linear mixed-effects models that tested a suite of variables associated with fire behavior, including: wildfire characteristics; fuel break treatment type, maintenance and accessibility; surrounding landcover; fuel loadings; soil conditions; weather; and topography.
Results/Conclusions
We identified over 2400 wildfire events associated with fuel breaks. On their own, fuel breaks did little to halt wildfires or alter their behavior. However, preliminary results indicate that larger fire size, smaller proportions of fuel breaks encountered by fire, and highly productive soil types at higher elevations reduced the probability of fuel break success. In contrast, fuel breaks located at lower elevations characterized by low lower fuels-loads and with likely greater accessibility for fire suppression and initial attack increased success probability. We also found variation in the effectiveness related to different treatment types, whereby fuel breaks either planted with fire resistant perennial vegetation (“green strips”) or stripped of vegetation (“brown strips”) had higher effectiveness than mowed fuel breaks when breached by wildfire. This novel study can help managers ultimately identify areas best-suited for targeted fuel break installations and better assess associated trade-offs between probable fire suppression effects and disturbance to sagebrush ecosystems produced by fuel break installation and maintenance. Findings are preliminary and provided for timely, best science.