Human-started wildfires expand the fire niche across the United States
Document Type: Journal Article
Author(s): J. K. Balch; B. A. Bradley; J. T. Abatzoglou; R. C. Nagy; E. J. Fusco; A. L. Mahood
Publication Year: 2017

Cataloging Information

  • Anthropogenic Wildfires
  • climate change
  • data set
  • Earlier
  • fire regimes
  • fire starts
  • forests
  • fuel moisture
  • human caused fires
  • ignition
  • ignitions
  • impacts
  • Increase
  • lightning caused fires
  • Modern Fire Regimes
  • regimes
  • severity
  • wildfire causes
  • wildfires
Record Maintained By:
Record Last Modified: June 1, 2018
FRAMES Record Number: 55551
Tall Timbers Record Number: 33613
TTRS Location Status: Not in file
TTRS Call Number: Available
TTRS Abstract Status: Okay, Fair use

This bibliographic record was either created or modified by the Tall Timbers Research Station and Land Conservancy and is provided without charge to promote research and education in Fire Ecology. The E.V. Komarek Fire Ecology Database is the intellectual property of the Tall Timbers Research Station and Land Conservancy.


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, where as 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.

Online Link(s):
Balch, J. K., B. A. Bradley, J. T. Abatzoglou, R. C. Nagy, E. J. Fusco, and A. L. Mahood. 2017. Human-started wildfires expand the fire niche across the United States. Proceedings of the National Academy of Sciences of the United States of America, v. 114, no. 11, p. 2946-2951. 10.1073/pnas.1617394114.