Winter grazing can reduce wildfire size, intensity and behaviour in a shrub-grassland

An increase in mega-fires and wildfires is a global issue that is expected to become worse with climate change. Fuel treatments are often recommended to moderate behaviour and decrease severity of wildfires; however, the extensive nature of rangelands limits the use of many treatments. Dormant-season grazing has been suggested as a rangeland fuel treatment, but its effects on fire characteristics are generally unknown. We investigated the influence of dormant-season (winter) grazing by cattle (Bos taurus) on fuel characteristics, fire behaviour and area burned in Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) shrub-grassland communities in south-eastern Oregon, USA. Winter grazing was applied for 5 years before burning and compared with ungrazed areas. Winter grazing decreased fine fuels and increased fine fuel moisture, which reduced flame height and depth, rate of spread and area burned. Winter-grazed areas also had lower maximum temperature and heat loading during fires than ungrazed areas, and thereby decreased risk of fire-induced mortality of important herbaceous functional groups. These results suggest that winter grazing may be a fuel management treatment that can be applied across vast shrub-grasslands to decrease wildfire risk and fire intensity to mediate climate change effects on wildfire activity.