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UM study: longer dry seasons leading to more severe fires

August 25, 2018

Changes in precipitation patterns have had direct impacts on the duration and severity of wildfires in the western United States, according to a recent study.

A team of scientists from the United States Forest Service and the University of Montana worked together on a study that examined summer rainfall totals in the western U.S. from 1979 to 2016.

Those studies showed that recent burn areas strongly correlate with a decrease in rainfall across approximately 31 to 45 percent of forested areas in 11 western states.

“Obviously, we’ve seen a dramatic increase in fires in the west and now we’re used to seeing long stretches without rain,” said Zack Holden, a scientist with the U.S. Forest Service who was the lead author on the study.

The research has shown that significant drops in summer precipitation and lengthening summer dry spells are major drivers of the increase in fire activity.

Previously, the belief was that the increase in fires was mainly due to warming temperatures and earlier snowmelt.

“Summer dry periods are tightly coupled to how warm and dry the air is during the fire season,” Holden said. “Longer windows without rain lead to more surface heating, which dries out woody fuels.

“It’s important to understand what drives forest fires.”

Holden said the Forest Service developed a plan that calls for building more fire-adaptive communities and thinning and harvesting more timber. He also said these conditions could lead to more fires at higher elevations, which would be more difficult to battle.

Charlie Luce, a USDA Forest Service research hydrologist and co-author of the study, said the maps of declining precipitation could help determine future drought patterns.

“Those can help us focus work near communities likely to experience continuing declines,” Luce said.

“This new information can help us better monitor changing conditions before the fire season to ensure that areas are prepared for increased wildfire potential. Further, it may improve our ability to predict fire season severity,” said Matt Jolly, USDA Forest Service research ecologist and co-author of the study.

The study was conducted as part of a larger project aimed at improving wildfire danger and drought monitoring.

UM hydrology and hydrologic modeling Associate Professor Marco Maneta was also a co-author.

“Decreases in precipitation and the increasing length of dry spells during the summer - a time when crop water demand in the arid west are highest - is not only exacerbating wildfires but could also have serious implications for western agriculture, especially in states highly reliant on rain-fed crops,” Maneta said.

The research was conducted by a team of scientists from the USDA Forest Service and the University of Montana, funded by NASA and the USDA, and was published this week in the Proceedings of the National Academy of Sciences.

The paper is online at http://www.pnas.org/content/

Reporter Scott Shindledecker can be reached at 758-4441 or at sshindledecker@dailyinterlake.com. early/2018/08/14/1802316115.

Reporter Scott Shindledecker can be reached at (406) 758-4441 or sshindledecker@dailyinterlake.com.

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