Human-started wildfires expand the fire niche across the United States

By Jennifer K. Balch, Bethany A. Bradley, J. Abatzoglou, R. C. Nagy, Emily J. Fusco, Adam L. Mahood. Proceedings of the National Academy of Sciences of the United States of America, 2017

860 citations recorded by the source corpus.

Significance Fighting wildfires in the United States costs billions of dollars annually. Public dialog and ongoing research have focused on increasing wildfire risk because of climate warming, overlooking the direct role that people play in igniting wildfires and increasing fire activity. Our analysis of two decades of government agency wildfire records highlights the fundamental role of human ignitions. Human-started wildfires accounted for 84% of all wildfires, tripled the length of the fire season, dominated an area seven times greater than that affected by lightning fires, and were responsible for nearly half of all area burned. National and regional policy efforts to mitigate wildfire-related hazards would benefit from focusing on reducing the human expansion of the fire niche. The economic and ecological costs of wildfire in the United States have risen substantially in recent decades. Although climate change has likely enabled a portion of the increase in wildfire activity, the direct role of people in increasing wildfire activity has been largely overlooked. We evaluate over 1.5 million government records of wildfires that had to be extinguished or managed by state or federal agencies from 1992 to 2012, and examined geographic and seasonal extents of human-ignited wildfires relative to lightning-ignited wildfires. Humans have vastly expanded the spatial and seasonal “fire niche” in the coterminous United States, accounting for 84% of all wildfires and 44% of total area burned. During the 21-y time period, the human-caused fire season was three times longer than the lightning-caused fire season and added an average of 40,000 wildfires per year across the United States. Human-started wildfires disproportionally occurred where fuel moisture was higher than lightning-started fires, thereby helping expand the geographic and seasonal niche of wildfire. Human-started wildfires were dominant (>80% of ignitions) in over 5.1 million km2, the vast majority of the United States, whereas lightning-started fires were dominant in only 0.7 million km2, primarily in sparsely populated areas of the mountainous western United States. Ignitions caused by human activities are a substantial driver of overall fire risk to ecosystems and economies. Actions to raise awareness and increase management in regions prone to human-started wildfires should be a focus of United States policy to reduce fire risk and associated hazards.

Subfields: Ecology, Global and Planetary Change, Safety, Risk, Reliability and Quality

View Paper: https://www.semanticscholar.org/paper/080c8ea7e54c99c0f5ac43b4cfb97d3662821769

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Citations in the corpus

Climate change is increasing the likelihood of extreme autumn wildfire conditions across California (2020, background): “)— across geographies and biomes [11, 12], and even when limited to lightning-caused fires [13, 14]— suggests that demographic and forest management factors alone are insufficient to explain themagnitude of the observed increase in wildfire extent over the past half-century.”
Influences of fire–vegetation feedbacks and post‐fire recovery rates on forest landscape vulnerability to altered fire regimes (2018, background): “↑ λ1 Increased ignitions or the targeting of ignitions in space and/ or time to coincide with fuel flammability; increases annual area burned Balch et al. (2017), McWethy et al.”
Assessing changes in global fire regimes (2023, background): “…modified vegetation type and density for 77% of the Earth’s terrestrial surface, primarily through agriculture, with myriad consequences for fuel characteristics and ignition sources (Balch et al., 2017a; Bowman et al., 2011; Marlon et al., 2008; Słowiński et al., 2022; Watson et al., 2018).”
Invasive grasses: A new perfect storm for forested ecosystems? (2020, background): “suppression, intense insect and pathogen outbreaks, increased anthropogenic ignitions, and other human disturbances (Dennison et al., 2014; Stephens et al., 2014; Jolly et al., 2015; Jones et al., 2016; Westerling, 2016; Balch et al., 2017; Stephens et al., 2018).”
Focus on changing fire regimes: interactions with climate, ecosystems, and society (2020, background): “One of the regions with the largest increases in wildfire globally is the western US (Dennison et al 2014, Westerling 2016, Balch et al 2017).”
Rapid growth of the US wildland-urban interface raises wildfire risk (2018, background): “While fires are an integral part of many ecosystems and the Earth system as a whole (6), humans have changed fire regimes globally (7) and throughout the United States (5), and climate change will increase fire frequency in the future, including in the WUI (8).”