, Volume 12, Issue 1, pp 16-32

First online:

Quantitative Evidence for Increasing Forest Fire Severity in the Sierra Nevada and Southern Cascade Mountains, California and Nevada, USA

  • J. D. MillerAffiliated withFire and Aviation Management, USDA Forest Service, Pacific Southwest Region
  • , H. D. SaffordAffiliated withUSDA Forest Service, Pacific Southwest RegionDepartment of Environmental Science and Policy, University of California Email author 
  • , M. CrimminsAffiliated withDepartment of Soil, Water and Environmental Science, University of Arizona
  • , A. E. ThodeAffiliated withSchool of Forestry, Northern Arizona University

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Recent research has concluded that forest wildfires in the western United States are becoming larger and more frequent. A more significant question may be whether the ecosystem impacts of wildfire are also increasing. We show that a large area (approximately 120000 km2) of California and western Nevada experienced a notable increase in the extent of forest stand-replacing (“high severity”) fire between 1984 and 2006. High severity forest fire is closely linked to forest fragmentation, wildlife habitat availability, erosion rates and sedimentation, post-fire seedling recruitment, carbon sequestration, and various other ecosystem properties and processes. Mean and maximum fire size, and the area burned annually have also all risen substantially since the beginning of the 1980s, and are now at or above values from the decades preceding the 1940s, when fire suppression became national policy. These trends are occurring in concert with a regional rise in temperature and a long-term increase in annual precipitation. A close examination of the climate–fire relationship and other evidence suggests that forest fuels are no longer limiting fire occurrence and behavior across much of the study region. We conclude that current trends in forest fire severity necessitate a re-examination of the implications of all-out fire suppression and its ecological impacts.


California fire ecology fire severity burn severity Sierra Nevada Sierra Nevada Forest Plan Amendment relative differenced Normalized Burn Ratio