Dec 11, 2017

What fire researchers learned from Northern California blazes

California
USA
by
Elizabeth Shogren
,
High Country News
A prescribed burn at California’s Bouverie Preserve last spring cleared tall grasses and downed limbs from around the giant old oak trees. Photo: Justin Sullivan, Getty Images
A prescribed burn at California’s Bouverie Preserve last spring cleared tall grasses and downed limbs from around the giant old oak trees. Photo: Justin Sullivan, Getty Images

The acrid smell of charred wood still permeates the air as Sasha Berleman, a fire ecologist, and I walk along a dirt path up through the middle of a canyon in the Bouverie nature preserve in Sonoma Valley. On the left side, the earth is black as tar, and scorch marks as tall as a person scar the trunks of the mature oak trees scattered throughout the field. But on the right side, the ground is tan and brown, and you have to look hard at the still-green oaks to see any evidence of the fire that raged through here just a few weeks before. It’s no mystery to Berleman why the fire behaved so differently on the two sides of the trail at Audubon Canyon Ranch’s Bouverie Preserve. When flames hit the field on the left of the path, they met a dense wall of thigh-high grass that hadn’t been mowed, grazed or burned for 20 years. The flames must have been 5 or 6 feet tall. On the right side, however, Berleman had set a prescribed burn just this spring.

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For more than a century, people have been snuffing out fire across the West. As a result, forests, grasslands and shrub lands like those in the Bouverie reserve are overgrown. That means that, when fire escapes suppression, it’s more destructive. It kills more trees, torches more homes and sends far more carbon into the atmosphere, contributing to climate change.

The devastating fires that hit Bouverie and a large swath of Northern California’s wine country in October killed 42 people and destroyed nearly 7,000 buildings. In California’s Sierra Nevada in recent years, megafires have burned at much greater severity than those forests ever saw in the past, killing trees across large landscapes and unleashing enormous quantities of carbon. The remedy, Berleman and many other scientists say, is to reintroduce fire to the landscape by allowing more natural fires to burn and setting controlled burns when weather conditions minimize the risk of a catastrophic blaze.

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Further complicating the picture is climate change — the major factor behind the longer fire seasons and bigger fires. This creates a feedback loop, where megafires exacerbate climate change, which then encourages even bigger wildfires. One study found that from 1984 to 2015, climate change doubled the area burned by wildfires across the West, compared to what would have burned without climate change.