Even in a state with a fire season and forests that have adapted to fire, this was bad. And while the 2020 wildfires have been the worst we’ve seen in the West, they’re not going to get better anytime soon. Forests are a complex system, and so there are many reasons for more fires over a longer season, such as ignition sources (like lightning or downed power lines), forest management and climate change.

Climate change is the biggest factor, according to Stanford University climate researcher Noah Diffenbaugh. He was lead author on a paper published in the August issue of Environmental Research Letters that found that over the last four decades, the area burned by wildfires in California each year has increased tenfold. That’s a 1,000 percent increase annually on average. “About half of the increase is attributed to global warming,” he says. He also notes that four of the five largest fires in California history were burning at the time of our interview in September 2020.

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The study found that California has seen an increase in average temperature of about 1.8 degrees Fahrenheit (1 degree Celsius) and decreases in average precipitation of about 30 percent over four decades. Those numbers add up to the number of fall fire days with an extreme chance of fire being double what they were in the early 1980s.

In Oregon — as well as Alaska, the Northwest, the Southwest and the Great Plains — average temperatures are up by about 1.5 degrees Fahrenheit (0.8 degrees Celsius). When the fires began this year, 80 percent of the state was in at least a moderate drought, and we’ve had a state of drought every year since 2000 but one. Drought stresses trees, and stressed trees have a harder time fending off diseases and insect infestations. Those trees die. Dead trees don’t absorb the carbon dioxide created by burning fossil fuels. Dead trees also burn very easily.

When fires burn intensely enough to reach the crowns of tall trees, it can exacerbate the climate change that’s causing larger fires in the first place. According to the 2018 National Climate Assessment:

Wildfires can also increase forest openness by killing midstory and overstory trees, which promotes earlier snowmelt from increased solar radiation. This, in turn, leads to more winter runoff and exacerbates dry summer conditions, especially in cooler interior mountains.

Forestry Management and Fire Suppression

There’s another factor in these large intense fires: The fact that we rush to put them out. Over the past century or so, fire suppression efforts have been too effective. By putting out every single wildfire, even those that don’t threaten homes or other infrastructure, we’ve allowed fuel to accumulate in the forest. The U.S. Forest Service noted that “frequent, low- to moderate-intensity fire” is a key ecosystem process.

Diffenbaugh, along with many other climate change and wildfire experts, agrees with that assessment. “Humans have been managing vegetation and managing fires for millennia,” he says. He went on to explain that there’s a long history of both scientific research and indigenous practices that have provided a lot of evidence for which approaches to wildfire risk work, including controlled burns. Forestry practices that reduce fuel also reduce the chance that fires will reach the crowns of adult trees. Controlled burns and smaller, more frequent fires could eventually bring us back to the pre-fire-suppression baseline.

This isn’t something that can be reversed in a year or two, though. By some estimates, we’d need to allow 20 million acres to burn at lower intensities in order to correct a century of overly zealous wildfire suppression.

Using controlled burns to address fuels and taking steps to address climate change, such as adhering to the 2015 Paris Agreement, could reduce wildfire risk by 2050. But we can’t forget the humans involved. The 79 percent of the fires burning on forestry lands in Oregon in 2020 were human caused. That means anything from a downed powerline to a spark from a car’s dragging exhaust pipe or the blade of a lawn mower striking a rock.

“All fires result from multiple ingredients coming together,” Diffenbaugh says. “This is also true for effective solutions. The answer to what is causing wildfire risks has multiple dimensions, and what will reduce risk also has multiple dimensions. Is it one or the other? The answer for the cause and the answer for the solution is always in the intersection.”

On a Thursday night, thunderstorms finally arrived in northwest Oregon and swept the smoke out of the valley. The fires were still burning — and they would burn for weeks — but firefighters were gaining ground and beginning to contain even the largest of them. Many people who had evacuated were allowed to return to their homes. And in Portland, we could finally open our windows and let in fresh air.

This story is part of Covering Climate Now, a global journalism collaboration strengthening coverage of the climate story.





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