Extent of human-ignited wildfires

A study analyzes the extent of human-ignited wildfires in the United States. Climate change has been linked to increased US wildfire activity in recent decades, but the human role in igniting wildfires remains unclear. To determine the geographic and seasonal extent of human- and lightning-ignited wildfires in the coterminous United States, Jennifer Balch and colleagues examined more than 1.5 million government-recorded wildfires that were extinguished or managed by government agencies from 1992-2012. The authors found that human-ignited fires accounted for 84% of all wildfires and 44% of all burned areas. Furthermore, the human-ignited fire season was three times longer than the lightning-ignited fire season, and added an average of 40,000 wildfires per year. Human-ignited and lightning-ignited wildfires were dominant in over 5.1 million km2 and 0.7 million km2 of the coterminous United States, respectively. Wildfires were more likely to be human-ignited than lighting-ignited as fuel moisture increased, expanding the geographical and seasonal extent of wildfires. According to the authors, enacting policies that raise awareness in regions prone to human-ignited wildfires may help reduce fire risk and associated hazards. - Read at PNAS

Article #16-17394: “Human-started wildfires expand the fire niche across the United States,” by J.K. Balch et al.