Cooler, wetter parts of Pacific Northwest likely to see more fires

(FEBRUARY 29, 2024) Forests in the coolest, wettest parts of the western Pacific Northwest are likely to be at risk this year. Dangers include increases in burn probability, fire size, and number of blazes. That's because the climate continues to get warmer and drier, according to new modeling led by an Oregon State University scientist. The study's lead author, Alex Dye, says this is important to study. We need to adapt to the changes in order to keep people, animals, and property safe.

Dye is a faculty research associate in the OSU College of Forestry. He worked with the U.S. Forest Service. They conducted wildfire simulation for more than 23 million acres of forest land west of the Cascade Range crest in Oregon and Washington. The simulations showed that by the 30-year period beginning in 2035, many areas could see at least twice as much fire activity as was observed during the prior 30 years.

Forests in all of the affected areas are key parts of multiple socio-ecological systems in the Northwest, Dye said. That means more fire will likely put pressure on everything from drinking water sources and timber resources to biodiversity and carbon stocks.

“The moist, highly productive forests of the Northwest don’t get fire as often as other parts of the West, like California or eastern Oregon,” Dye said. “But fire does naturally occur in the PNW ‘Westside’ as we call it –  the fire regimes are actually quite complex in this region. It can be challenging to assess fire probability in an environment where there isn’t a lot of empirical information about the fire history to build models.”

Because the Westside doesn't usually have many fires, people don't think of the risks as high. And scientists don't often focus on this region. But recent big blazes such as those that occurred in the Northwest around Labor Day 2020 showed what can happen when severe fire strikes Westside areas.

“And what if fires like that were to start happening more frequently in the near future?” Dye said. “What if that once every 200 years became once every 50 years, or once every 25 years as climate change brings hotter and drier conditions to the region?”

Climate is just one factor influencing wildfire, he noted, but it is an important one. He sees the findings as a crucial planning tool to help the Northwest prepare for a rapid acceleration of fire over the next few decades.

“Describing the possibilities of how, when and where climate change could affect fire regimes helps bracket everyone’s expectations,” he said. “Particularly important among our findings are new insights into the possibility of shifts towards more frequent and large fires, especially those greater than 40,000 [99,000 acres] hectares as well as shifts toward more fires burning at the beginning of fall when extreme weather has the potential to increase fire spread."