The effects of wildfires are long lasting and pernicious. Ecosystems and economies can take years, even decades, to fully recover. But fires in the forest can cause other, previously unseen, disturbances to the ecosystem.

Areas that have burned see an increase in the pace of snowmelt for as many as 15 years after the flames go out, according to a study published last week in the journal Nature Communications by researchers from Portland State University.

Kelly Gleason, lead author and assistant professor at Portland State, said the impacts are far-reaching and can endure for years.

“This fire effect on earlier snowmelt is widespread across the West and is persistent for at least a decade following fire,” she said in a statement. Her team found that, on average, snow in burned areas melted five days earlier than in areas that did not burn.

Like most things having to do with fire and ice, it all comes down to heat.

When a fire burns through an area, the loss of foliage means less shade and more direct sunlight on the snow. Black soot from burned trees and shrubs absorbs more heat from the sun than the otherwise white surface of snow. Increased heat absorption means faster snowmelt.

"Snow is typically very reflective, which is why it appears white, but just a small change in the albedo or reflectivity of the snow surface can have a profound impact on the amount of solar energy absorbed by the snowpack," said co-author Joe McConnell, a hydrology professor at the Desert Research Institute in Reno, Nevada. "This solar energy is a key factor driving snowmelt."

Researchers found that 11 percent of forests across the Western U.S. are seeing earlier snowmelt as a result of wildfires.

In many places across the arid west, snowpacks act as reservoirs, providing crucial water for agriculture, hydroelectric power and recreation. It also acts as a bulwark against future fires, keeping essential moisture in ecosystems that are prone to fire.

That moisture loss — coupled with hotter, drier fire seasons fueled by climate change — can be the jumping off point for a catastrophic feedback loop, Gleason said.

"Snow is already melting earlier because of climate change," she said. "When it melts earlier, it's causing larger and longer-lasting fires on the landscape. Those fires then have a feedback into the snow itself, driving an even earlier snowmelt, which then causes more fires. It's a vicious cycle."

-- Kale Williams

kwilliams@oregonian.com

503-294-4048

@sfkale

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