Arizona Public Radio | Your Source for NPR News
Play Live Radio
Next Up:
0:00 0:00
Available On Air Stations
Science and Innovations

Thinning the Forest, Part 1: Prescription

Melissa Sevigny

Northern Arizona is home to the largest ponderosa pine forest in the world. If you’ve ever hiked through it, you’ve probably seen trees marked with brightly colored paint. That paint is a kind of map for the logging companies that thin the woods and make them more fire-resistant. But which trees get to stay and which have to go—and who makes those decisions? KNAU’s Melissa Sevigny reports.

Devon Suarez grew up in Heber and his family has been in the logging business since the sixties. He always wanted to follow that tradition. "I guess it was always a little dream I had," he says. "I used to play cars with my best friend, we had our own logging company and all that. So I guess it finally came true!"

Credit Melissa Sevigny
Devon Suarez, contractor

He started Suarez Forestry last year and has a contract to clear trees at the Chimney Springs restoration site north of Flagstaff. Suarez says there are a lot of misconceptions about what he does. "We’re not clear cutting, we’re not taking old growth. We are thinning the forest to make it healthier."

But how do you create a healthy forest? Loggers like Saurez are guided by splashes of paint on the pines: orange for “leave” trees and blue for “cut” trees. The paint’s put there by a Forest Service timber marking crew. Saurez used to work on one before he started his own company.

"Making those decisions, I think it comes with a huge responsibility," Suarez says. "Even when I was timber marking I’d say, man, that’s a lot of power for one person." 

Credit Melissa Sevigny
Trees marked with orange paint at Chimney Springs
Credit Melissa Sevigny
Logs waiting for transport

But Saurez isn’t alone in making these choices. The process starts with a “prescription”—like a doctor’s prescription, but for trees. Mark Nabel, a silviculturist for the Coconino National Forest, says, "It’s really where the art and science come together. You’re trying to leave a condition that looks somewhat natural but also reduces the risk of fire and has value for wildlife."

It’s a balancing act to meet all of those goals. Nabel walks through a site and decides how big the tree groups should be and how much space should be cleared between them. Spacing matters because the whole idea is to prevent wildfires from climbing into the crowns and leaping from one clump to another.

But Nabel says there’s wiggle room for aesthetic considerations. "If they’ve got forks or they’ve got some odd shape to them we might leave those trees just because they provide a little bit of visual diversity across the landscape," he says.

This prescription is handed to a timber marking crew. They fan out through the forest with cans of spray paint. But this site, Chimney Springs, is a testing ground for a more modern method.  

Neil Chapman, program manager for The Nature Conservancy, explains: "Instead of a spray can they’ve got a tablet."

Credit Melissa Sevigny
Mark Nabel and Neil Chapman

The Nature Conservancy partnered with the U.S. Forest Service and logging contractors to experiment with forest thinning practices. He says paint is the time-honored traditional method, but it’s expensive and slow. Switching to digital maps on computer tablets could cut marking costs in half. "They’re just communicating it differently," Chapman says. "So instead of communicating what trees to take and what trees to leave with paint, they’re creating maps that they can share with the logger that do that."

It’s one small tweak to the process that Chapman hopes will speed up restoration work in northern Arizona, which has been plagued by high costs and missed deadlines.

"Accelerating the pace and scale of this restoration work is really important to make sure that we prevent the catastrophic fires, as much as possible, as soon as possible," he says.

And to make sure the forest that’s left behind after thinning is the one Arizonans want.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
Related Content