Why is fire 5 times more likely to burn in the Great Basin than the Colorado Plateau?

Fire is five times more likely to burn in the northern Great Basin than in the southern Great Basin and Colorado Plateau (Littell et al. 2009). While the abundance and distribution of invasive annual grasses are likely influencing present-day regional fire occurrences in the northwestern Great Basin, Columbia Basin, and Snake River Basin, they do not represent the only reason for increased fire frequency in these regions. Seasonal patterns of lightning ignitions in the northwestern Great Basin coincide with the season of peak surface fine fuel abundance and low fuel moisture content (Miller et al. 2019, see maps 3-18, pg. 114).

Large western fire events (more than 1,000 acres) between 2000-2014. Depicted are fire event timing (month of start) and percentage of summer precipitation (Derived from David Board 2018)