Road map for adapting dry forests to new fire regimes

In a paper published this week in Ecological Applications, Andrew Merschel, James Johnston and Meg Krawchuk of the OSU College of Forestry also join other researchers in acknowledging the role of Indigenous fire stewardship in past and present landscapes and the value of restoring that stewardship -- intentional low-severity burning that reduces fuels and is important culturally.

The Oregon State team was among dozens of scientists across the western United States who teamed up on three papers that the journal published simultaneously, all dealing with approaches for managing fire-dependent forests following a century of fire suppression and in the face of climate change. Collectively the scientists analyzed more than 1,000 published papers going back more than 100 years.

"Exceptionally hot, dry weather has already fueled dozens of fires across the west in 2021, including the 400,000-acre Bootleg fire in south central Oregon," said Krawchuk, a forest ecologist who has been researching approaches for societal adaptation to fire for years. "A hundred years of federal policy that prevented regular surface fires in these forests has led to forests that are too dense and packed with brush and allow fires to ignite and spread easily. Our team wants to give land managers and others across the region a clear picture of the best available science and how they can use it to make good decisions about managing landscapes."

Krawchuk, Merschel and Johnston collaborated with lead author Keala Hagmann of the University of Washington and others to provide a framework for assessing changes in landscape conditions since suppression became the basis for federal forest fire policy following the Great Fire of 1910. That blaze killed 87 people, destroyed several towns and burned an area roughly the size of Connecticut -- 3 million acres of forest in Idaho, Montana, Washington and British Columbia.

"We helped summarize knowledge about how fire shaped the landscape for hundreds of years using a variety of sources, including historical records and tree ring research," Johnston said. "We've shown that millions of acres of forest have significantly departed from their historical condition and need restoration."

Vegetation patterns in fire-excluded areas tend toward homogenous, with generally more dead vegetation both on the ground and in the canopy, which means more fuel.

"Current conditions are much more vulnerable to the direct and indirect effects of seasonal and episodic increases in fire and drought, especially in a climate that's rapidly warming," Merschel said. "But management that realigns or adapts fire-excluded conditions to the increases in fire and drought can help ecosystems and human communities."

Merschel notes that at nearly 414,000 acres, the Bootleg fire covers almost half as much acreage as burned in Oregon during the entire 2020 fire season and describes it as an "ecological catastrophe."

"Early reconnaissance indicates an almost total mortality of trees, most significantly the old growth trees that make up the structural backbone of forest ecosystems," Merschel said. "This didn't have to happen and similar disasters don't have to happen again if we as a society decide to invest in ecologically based forest restoration and climate and wildfire adaptation strategies. Those sorts of investments would dampen the intensity of the fires and create more options for communities and forests."

Merschel said that historical records for nearly 1 million acres of fire-dependent ponderosa pine forests show that prior to 1918, a surface fire burning more than 200,000 acres happened about every 15 years. The frequent fires resulted in minimal fuel accumulation and led to forests that were resistant to fire and drought, with trees commonly 300 years old or older.

"Ignoring how frequent fire made those outcomes possible will continue to have tragic consequences," he said. "We can't rely on suppression to prevent megafires in fire-dependent forests. We need restoration that includes careful reintroduction of low-intensity surface fires as part of a viable strategy for adapting forests and communities to climate change, and our window for implementing them is closing fast."