Researchers point to climates change’s dramatic effects
The forests that surround the Methow Valley will look very different in a future shaped by rapidly advancing climate change, according to two fire ecology researchers who led a “Wildfire Walk” through forests of the Twisp River drainage last week.
Hosted by the Methow Conservancy, the walk provided perspectives on the past, present and future of Methow Valley forests from Susan Prichard, a Methow Valley resident and fire ecologist with the University of Washington, and Paul Hessburg, a landscape ecologist with the U.S. Forest Service’s Pacific Northwest Research Station.
The walk began at the Twisp River Sno-Park, on U.S. Forest Service land about 12 miles upriver from Twisp. Hessburg had sober warnings about the effects of climate change on the dry forests of eastern Washington. Gesturing to surrounding stands of Douglas fir and ponderosa pine trees, he predicted a changed landscape by 2050 due to reduced snowmelt and moisture.
“This forest is going to change tremendously. There will just not be enough water …to grow these forests. The ponderosa pine will be the dominant species” because it has a tap root that allows it to survive with less water than other species, he said.
“The evidence is so overwhelming that we have to have a discussion about what we want for our forests,” Hessburg said. “We’re in a world of hurt and I’m deeply concerned we will not use our time to (protect) forests as glorious as these in the upper watershed.”
Altered by suppression
Forests in this region have been altered by years of fire suppression, becoming more densely packed with trees, said Prichard, who has studied how forest management practices like thinning and prescribed burning impact forests’ ability to survive wildfires.
Historically, naturally reoccurring small and medium fires helped prevent fuel buildup and created a patchwork or mosaic pattern in forests, with burned areas that created natural fire breaks that limited the spread of wildfires, Prichard said. But increasingly today, Western forests are experiencing massive wildfires that devastate large swaths of forest, a phenomenon that is exacerbated by climate change.
Indigenous people in the West recognized the benefits of fire on the landscape, and would routinely set fires in spring to clear underbrush, open up land for grazing and crops, and prevent larger fires, Hessburg said. “Fire exclusion started when tribes were moved from the landscape,” he said.
Wildfire suppression policies adopted by the Forest Service in the early 1900s have meant that natural fires have been suppressed for decades, allowing forests to become unnaturally dense and more vulnerable to massive fires, Hessburg said.
Missing the mosaics
“We are missing the small to medium mosaic fires,” Prichard said. “We’re used to seeing understories like this,” she said, pointing to stands of closely growing trees and forest floors thick with underbrush and dead wood.
“A patchwork of meadows, shrublands and open savannahs are critical components of forest survival,” Hessburg said.
The impacts of climate change and drought are already being seen in the region, with evidence of “drought injury” to trees in the Entiat and Chelan drainages, making them more vulnerable to disease and insect infestations, Hessburg said.
Walking beside the Twisp River, he pointed to Douglas fir trees that are infested with dwarf mistletoe, a parasite that can kill the trees. The mistletoe acts as a “ladder fuel” for fire, carrying fire from the forest floor up into the canopy of the tree where it would “burn like a roman candle” and spread to surrounding trees, Hessburg said.
Other Douglas fir trees in the area have been killed by pole beetles, which attack “low vigor trees” weakened by lack of water, he said. “This is an early indication that those trees are not matched to the site … and they seeded-in 20 to 30 years ago,” he said.
Threatened by beetles, pathogens, drought and fire, landscapes like the Twisp River drainage need treatments like thinning and prescribed burning to make them more resilient in the face of climate change, the researchers said.
Hessburg said those treatments should “discriminate against Douglas fir trees,” which he described as “a weed, a dandelion, a cockroach in the tree kingdom.”
“I’m strongly advocating (treatments) in low-elevation forests chock-full of fuel … thinning allows us to bring fire back” through prescribed burning, Prichard said. “A colleague described prescribed burning as giving the forest a bath.”
About 20 people participated in the Wildfire Walk, which was co-hosted by the Okanogan Conservation District and Fire Adapted Methow Valley.