Pile Burning Explained

Lately, you may have seen smoke coming out of the Ashland Watershed on cold and rainy days. We’ve been hard at work conducting pile burns, which are an example of “good fires” that can prevent “bad fires” in your forest. Here’s why… 

Smoke from a pile above Ashland on a January morning. (Photo by Evan Barrientos/The Nature Conservancy)

Tree and brush thinning is an essential part of forest restoration and wildfire safety. By removing some of the dense vegetation in that accumulated during a century fire suppression, we make it  harder for ground fires to climb into the canopy, where they grow fast and intense. However, the branches and small logs cut down, referred to as slash, would actually increase fire danger during the summer if left in place.

Slash left over from thinning presents a fire hazard (and a mess) if left alone. (Photo by Evan Barrientos/The Nature Conservancy)

To lower wildfire risk and set the stage for beneficial fire, which are our ultimate goals, we need get rid of slash. The most effective and efficient way to do so is often to pile and burn it. After work crews finish thinning a site, they pile the slash and leave it to dry under polyethylene sheets. These sheets play the important role of helping piles dry. Studies show that properly covered piles burn more cleanly and efficiently compared to uncovered piles, which means the sheets actually reduce air pollution.

Piles drying in a thinned restoration unit. Once slash has been piled, it cures for a year in order to burn cleanly and efficiently. (Photo by Evan Barrrientos/The Nature Conservancy)

When autumn rains thoroughly soak the forest, we begin pile burning. Igniting hundreds of little bonfires in a forest may seem unsafe at first, but because piles stay dry under the polyethylene sheets they can be ignited when the rest of the forest is too wet to burn. This is why we time our pile burns with the wet season. Once lit, piles are monitored and tended by crews until completely extinguished.

A crew member ignites a burn pile on a snowy morning. Piles can burn under surprisingly wet conditions, which helps ensure safety. (Photo by City of Ashland)

After piles are reduced to ash, we’re left with a forest where wildfire response is safer and more effective. By burning fuels proactively, we can reduce fuels during weather that will carry smoke up and away from communities, an option that wildfires don’t give us. On a large scale, this lets us increase community fire safety and decrease the amount of smoke during summer. This type of planned, proactive burning is what we mean when we say “good fire prevents bad fire.”

Pile burn smoke rises up and away from Ashland under ideal weather conditions. This work reduces the risk of heavy smoke during the wildfire season. (Photo by City of Ashland)

Thinning and pile burning are important steps in the larger process of forest restoration. As we continue to conduct pile burns this year, you’ll occasionally see smoke in the air. Know that it’s coming from good fire that’s making our forest safer and healthier. To learn more about controlled burns, check out this fact sheet. To receive updates on when and where they’ll occur, click here.

Lead author: Evan Barrientos, Monitoring and Outreach Assistant, The Nature Conservancy


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