Despite large changes in forest management and fire suppression, climate strongly influences wildfire activity in the northern Rocky Mountains, according to research published by a team of University of Idaho and U.S. Geological Survey scientists.

The increase in wildfires in the past 30 years coincides with an increase in warm, dry summer conditions, according to the study. The same is true for a period in the early 20th century, including the dramatic fires of 1910. During a cooler, wetter period in the mid-20th century, fire activity decreased.

The team used previously published records documenting burned areas in Idaho and western Montana and compared fire patterns to seasonal climate records revealing the flammability of forest vegetation. The findings were published last week in the peer-reviewed journal PLOS ONE, in a paper lead by Philip Higuera, associate professor in the University of Idaho’s College of Natural Resources. 

Wildfires are a natural component of most forests across the 46,000-square-mile study region, and the team wanted to better understanding how climate relates to periods of widespread burning — and if and how the relationship between climate and wildfire activity changed over the last 110 years.  

While climate and fire have been tightly linked over the past century, the work also suggests increased burning over the past several decades has been larger than expected based on climate alone, potentially related to the lack of burning during the mid 20th century.

“Climate has enabled fire across the Northern Rockies for the past hundred-plus years despite the significant role that humans have played in managing our lands. Our results suggest climate variability and change will continue to shape fire activity across the forests of the interior northwest,” says John Abatzoglou, UI associate professor of geography and coauthor of the study.

With warmer, drier conditions predicted in the future, many scientists expect large wildfires will become more common. By understanding the links between climate and wildfires in the past, this study helps provide context for understanding current wildfires and how forests may respond to future climate change.

Much of the Northwest and Northern Rockies are already in “moderate” or “severe” drought this summer.

“The tight link between fire and climate documented by this research suggests the potential for an unusually large fire season across much of the region,” Higuera said.

Jeremey Littell, co-author on the paper, is a research scientist with the Alaska Climate Science Center. The project was funded by the National Science Foundation and the University of Idaho. 

University of Idaho Press Release