US Forest Service Study Finds Climate Significant Factor in Wildfires

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The recent increase in wildfires in the Western United States is due to a complex relationship between climate and fuels, not just higher temperatures or longer fire seasons, according to a study conducted by the U.S. Forest Service and university scientists. This is the most detailed examination of wildfire in different ecosystems so far and will appear in the current issue of the journal Ecological Applications.

"We found that what matters most in accounting for large wildfires in the Western United States is how climate influences the build up - or production - and drying of fuels," said Jeremy Littell, a research scientist with the University of Washington's Climate Impacts Group and lead investigator of the study. "Climate affects fuels in different ecosystems differently, meaning the future wildfire size and, likely, severity depends on interactions between climate and fuel availability and production."

Scientists used fire data from 11 western states and 19 ecosystems spanning the years 1916 to 2003 to look at the climate-fire relationship. They constructed models of total wildfire area burned and then compared those fire models with monthly divisional climate data from each state, according to a news release from the U.S. Forest Service Pacific Northwest Research Station.

The study confirms that in years with low precipitation and high temperatures, fuels dry out, resulting in more fires. It also provided new insight on the relationship between climate and fires. In shrubland and grassland, when there is high precipitation one year followed by dry conditions the next year, there are more fuels resulting in larger wildfires, according to the study.

"These data tell us that the effectiveness of fuels reductions in reducing area burned may vary in different parts of the country," said David L. Peterson, a research biologist with the Forest Service's Pacific Northwest Research Station and one of the study's authors. "With this information, managers can design treatments appropriate for specific climate-fire relationships and prioritize efforts where they can realize the most benefit."

Findings suggest that if the climate continues to warm, more areas in the northern portion of the West can be expected to burn. This corroborates what researchers projected in previous studies. Wetter areas like the west side of the Cascade Range, that are not as prone to fire now, may be more fire prone by mid-century if climate projections hold and weather becomes more extreme, according to the study.

To read the study, visit http://www.esajournals.org/doi/pdf/10.1890/07-1183.1.