A new study published in the International Journal of Wildland Fire found that, contrary to what has been claimed in some of the news coverage of recent forest fires, there is not a trend toward increasing fire severity in the Sierra Nevada. Previously, those who claimed that fire severity was increasing relied primarily on two publications by Jay Miller of the Forest Service (Miller et. al 2009, Miller and Stafford 2012).
However, Dr. Chad Hanson and Dr. Dennis Odion found that the Miller studies left out hundreds of thousands of acres of fire data from their analysis. In contrast, Hanson and Odion used all of the available fire severity data for the Sierra Nevada, and that data showed no trend toward increasing fire severity.
Furthermore, they found that rate of high severity fire since 1984 has been lower than it was historically. These results refute some of the main claims we see on this blog and elsewhere.
Research in the Sierra Nevada range of California, USA, has provided conflicting results about current trends of high-severity fire. Previous studies have used only a portion of available fire severity data, or considered only a portion of the Sierra Nevada. Our goal was to investigate whether a trend in fire severity is occurring in Sierra Nevada conifer forests currently, using satellite imagery. We analysed all available fire severity data, 1984–2010, over the whole ecoregion and found no trend in proportion, area or patch size of high-severity fire. The rate of high-severity fire has been lower since 1984 than the estimated historical rate. Responses of fire behaviour to climate change and fire suppression may be more complex than assumed. A better understanding of spatiotemporal patterns in fire regimes is needed to predict future fire regimes and their biological effects. Mechanisms underlying the lack of an expected climate- and time since fire-related trend in high-severity fire need to be identified to help calibrate projections of future fire. The effects of climate change on high-severity fire extent may remain small compared with fire suppression. Management could shift from a focus on reducing extent or severity of fire in wildlands to protecting human communities from fire.