Quantifying large-scale impacts of cattle grazing on annual burn probability in Napa and Sonoma Counties, California

This research paper examines the impact of cattle grazing on wildfire risk in Napa and Sonoma Counties, California, by quantifying changes in average annual burn probability under different grazing scenarios. The authors calculated burn probabilities for 2001–2017 using mixed-effects regression models combined with a range of grazing intensities and extents. Scenarios represented current grazing conditions, ungrazed conditions, adding grazing to high-priority landscapes, and grazing the full study area. 

The study estimated that under current grazing conditions, cattle grazing reduces average annual burn probability by 45% compared to ungrazed conditions, from 9.9% to 5.4%. Adding grazing to high-priority landscapes identified by CAL FIRE decreased average annual burn probability in those areas by 82%, from 7.6% to 1.4%, compared with current grazing conditions. Their findings suggest cattle grazing benefits the study area by reducing overall burn probability, and that extending its use to treat fuels in priority areas in and around the wildland-urban long-term interface could further reduce fire risk on community-adjacent lands. Land managers may find cattle grazing a valuable long term fuel-management tool at the landscape scale.