What Effects Tree Thinning Has On Wildfires NPR's Ari Shapiro talks to Matthew Hurteau, a forest ecologist at University of New Mexico, about the effectiveness of tree clearing and thinning in preventing wildfires or mitigating their intensity.

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What Effects Tree Thinning Has On Wildfires

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The Mendocino Fire in California is now the largest in the state's modern history, and it's just one of several wildfires consuming the state. The Trump administration wants to expand commercial logging in California's national forests. And the president has suggested that this could limit the intensity of wildfires. To understand the relationship between tree clearing and wildfires, Matthew Hurteau joins us now. He's a forest ecologist at the University of New Mexico. Welcome.

MATTHEW HURTEAU: Thank you, Ari.

SHAPIRO: What effect does tree thinning have on wildfires?

HURTEAU: The influence that thinning has is that it alters the way that fire interacts with the forest. So by reducing the number of small-diameter trees, you break what we call a fuel ladder from the forest floor into the canopy of the overstory trees. And then the other thing is is that the crowns of the overstory trees are further apart, which makes it more challenging for fire to move from one tree crown to the next.

SHAPIRO: Sounds like you're saying if the trees are a little less dense the fire will move a little less quickly. Is that right?

HURTEAU: Yeah. And generally speaking, it can stay - it stays on the forest floor, or is more likely to. It will only torch small groups of trees.

SHAPIRO: So if that's the impact of tree thinning, what about clearcutting, just kind of taking down a forest or a section of forest altogether?

HURTEAU: Yeah, so there is - I mean, you know, if we wanted to make a forest asbestos-proof, you could clear-cut them and pave it, right?

SHAPIRO: (Laughter) Hard to set fire to a parking lot.

HURTEAU: Yeah. The basic fact of the matter is if we do that, we lose the forest, and we lose all of the ecosystem services that forests not only provide to us but also in terms of, you know, having a functioning ecosystem in that place and habitat for wildlife, watershed protection and all that. So the - a lot of the forests, these dry forests that, like, are burning in California now, historically had relatively frequent fire in them. And it's an integral process in these systems. And if we go in and clear all the trees, you know, we haven't actually solved the problem.

SHAPIRO: You said that getting rid of smaller diameter trees makes a difference in terms of how fast a fire might spread, but I could imagine that if I'm a logging company, those smaller diameter trees are going to give me a lot less wood for the effort it takes to remove them.

HURTEAU: Yeah. When we - when we implement a thinning treatment on national forest lands and we're just taking what are called non-merchantable trees of small diameter because they don't have an economic value, per se, typically what happens is that those thinning operations are funded by taxpayer dollars. So the Forest Services management budget pays to remove those trees from the forest.

SHAPIRO: I know that environmental groups and logging companies are often at odds with one another. Do you think this is an area where they can kind of come to an agreement on a policy that makes everybody happy?

HURTEAU: So there are examples where these stakeholder groups have come together and agreed upon solutions to the, you know, the large hot wildfire challenge that we're facing. And there's a great example in the Dinkey Creek watershed in the Sierra Nevada where you have both conservation groups and, you know, forest products industry folks involved at the table, as well as tribal members and land managers and communities. And they have been able to navigate some of these challenges and come up with solutions that work for the group.

SHAPIRO: Matthew Hurteau is a forest ecologist at the University of New Mexico. Thanks for speaking with us today.

HURTEAU: Thank you, Ari.

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