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Planning for uncertainty: U.S. Forest Service prepares for climate change impacts on public lands

North Bridger logging

A slash pile near Fairy Lake Road can be seen below a recently logged section of the Custer Gallatin National Forest in the Bridger Mountains on Wednesday, Sept. 29, 2021.

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Areas where ponderosa pine forests burned years ago east of Livingston are showing little to no signs of recovery.

That’s according to Cathy Whitlock, Regents Professor Emerita of Earth sciences at Montana State University and co-lead on the newly released Greater Yellowstone Climate Assessment.

“There needs to be a seed-source for the forest to recover, and then those seeds need to become seedlings and develop into mature trees,” Whitlock said. “The concern is, at low elevations it’s just getting too dry for that to happen.”

Scientists predict that as drought and wildfire ramp up in the coming decades, forest ecosystems will change. In some parts of the Custer Gallatin National Forest, trees that die off may never grow back.

The Greater Yellowstone Climate Assessment, released this summer, describes past and projected climate-related changes in the 22-million-acre area that spans outward from Yellowstone National Park into northwest Wyoming, south central Montana and eastern Idaho.

Earlier snowmelt, loss of snowpack, longer growing seasons and reduced water availability will increase fire potential at all elevations through the middle of the century, according to the assessment.

The emerging conditions, combined with an increase in tree death due to various disturbances, could lead to rapid changes in forest ecosystems. At lower elevations, forested areas may become grasslands, it says.

At higher elevations, increased wildfire and bark beetle activity will change the composition of the forest. Over time, fast-growing trees that are better-adapted to wildfire will move into these areas, Whitlock said.

“It’s easy to lose trees because you just need a disturbance event,” Whitlock said. “The thing that will take decades is to see how the composition of the forest changes. You’re not going to notice it in a year, but you will notice it over the next few decades.”

Changes to tree cover, density and composition, especially at the upper and lower boundaries of forested areas, are already manifesting across the Custer Gallatin National Forest.

Across south-central Montana’s Ashland Ranger District, a series of uncharacteristically large wildfires resulted in a near 50% reduction in forest cover between the 1990s and 2012, said Gunnar Carnwath, the national forest’s plan revision ecologist.

“A lot of that (non-forested) area is likely going to regenerate naturally through planting efforts, but a lot of it is either not going to regenerate or will take a long time to regenerate,” he said.

At the upper reaches of the national forest, whitebark pine ecosystems are shrinking.

Warming conditions are exacerbating mountain pine beetle outbreaks and growth of the scaly, non-native blister rust fungus, which kills the high-elevation trees. Competition from shade-loving tree species like subalpine fir and wildfire are also causing the keystone pine species to decline, he said.

With more climate-driven changes looming, the U.S. Forest Service is finalizing a new land management plan for the Custer Gallatin National Forest, which will guide how the agency oversees the vast landscape for decades to come.

Spanning 3.1 million acres over two states — Montana and South Dakota — the national forest is one of the region’s most ecologically diverse, the Forest Service writes. It borders Yellowstone National Park along the park’s northern and western boundaries and holds about 1 million acres of wilderness.

Officials released a draft plan to the public in July, 2020. The broad, overarching document designates areas for conservation and recreation, guides uses of the forest and outlines strategies for wildlife management.

The Forest Service collected objections to the draft plan, then held meetings to hear from people who were against portions of it. People shared concerns about the draft plan’s vision for wilderness, wildlife management and land uses like recreation, logging and grazing.

Any changes to the draft plan in response to the objections are planned to be released in the final document, likely sometime this fall. There hasn’t been a forest plan revision since 1986 and 1987 — when the Custer and Gallatin National Forests were managed separately.

Maintaining the vast national forest’s “ecological integrity” as key stressors like climate change alter ecosystems is at the core of the new forest plan, according to Carnwath.

That means that unlike the 1986 and 1987 plans, managers designed the new plan in a way that aims to keep a set of specific, quantifiable ecological conditions out on the landscape, he said.

Those desired conditions include specific habitat characteristics that managers want to keep, like the types, sizes classes and distribution of trees in an area, for example.

If the agency can maintain this range of conditions across the landscape, then it can maintain habitat that supports the forest’s native plant and animal species, Carnwath said.

The Forest Service maintains that the draft plan’s direction will allow it to keep ecosystems healthy, but some feel the plan doesn’t allocate adequate forest protections, especially amid a rapidly-warming climate.


Custer Gallatin National Forest

Leverich Canyon Trail weaves its way into the Custer Gallatin National Forest on Sept. 29, 2021.

George Wuerthner, a photographer, ecologist and the author of dozens of books about environmental issues in the West, believes the draft plan gives the Forest Service too much leeway to tamper with forest ecosystems.

He worries that by logging and thinning trees often, the agency could inadvertently reduce forest resilience over time.

Human timescales are short, so it’s easier to consider what might happen on the landscape 50 years from now as the climate warms, but it’s harder to predict what might happen hundreds or thousands of years into the future, Wuerthner said.

“We need to be cautious in assuming we can manipulate the landscape and it won’t have consequences,” he said.

Trees have a varying genetic ability to adapt to and tolerate disturbances like wildfire, drought and pine beetle, so there’s a chance that frequent logging or forest thinning will take out stands of trees that have those adaptations, according to Wuerthner.

“We should allow natural evolutionary processes to occur without much manipulation of the forest,” he said. “Over time, trees that are more resilient to drought will regenerate, which will gradually increase forest resilience.”

Philip Higuera, an associate professor of fire ecology at the University of Montana, said that in a fast-warming climate, land management agencies face the challenge of determining when it’s best to resist inevitable changes, let those changes play out on their own or direct them over time.

There are scenarios where all three strategies make sense, he said.

In areas of high conservation value, managers often want to keep ecosystems from changing as long as possible. In remote areas like wilderness, taking a hands-off approach to management can make sense.

However, in many cases, doing nothing to direct change ignores important tools that managers have at hand to help humans more safely exist as conditions shift, Higuera said. Inaction on climate change over the past few decades now means people no longer have the luxury of doing nothing.

“There are a robust set of studies that demonstrate that one of the best ways to protect communities or values at risk is through fuels reduction treatments that are specifically aimed at modifying fire behavior,” he said.

Such treatments are already underway in the Bridger, Bangtail and Gallatin mountains outside of Bozeman, though the Bozeman Municipal Watershed project and North Bridgers Forest Health project were both approved under the old forest plans.

The municipal watershed project calls for approximately 4,700 acres of forest thinning and prescribed burning along the Gallatin front. Officials want to protect the city of Bozeman’s water, firefighters and homes in the event of a severe wildfire.

The North Bridgers project calls for about 2,300 acres of forest thinning and scattered clear cuts in the Bridgers and Bangtails. It was approved under a legal provision called a categorical exclusion. The provision allows managers to speed up projects in areas impacted by insects and disease.

Phil Knight, a conservation advocate from Bozeman and a member of Montanans for Gallatin Wilderness, said projects like those around Bozeman are problematic because they call for removal of large-diameter trees, which provide profitable timber.

Knight said that the older, large-diameter trees store more carbon, are aesthetically pleasing, provide important wildlife habitat and are more fire-resistant. Unlike dense stands of small-diameter trees, older, bigger trees cool the forest floor and block wind, which can decrease the likelihood of severe fire, he said.

Knight supports the parts of the municipal and North Bridgers projects that call for removal of smaller trees, but he’s noticed that much of the work involves cutting down old growth.

“That makes me wonder, is this really about getting some valuable timber and trees out of there or is it really about creating fire breaks?” he said. “It’s probably some of both.”

Higuera said that, generally, removing small-diameter trees from the understory decreases the likelihood of a surface fire turning into a crown fire. It also provides benefits to larger trees and gives firefighters more latitude in responding to a fire.

If managers are aiming to reduce fire hazard and protect communities, generally, they’d want to leave larger trees on the landscape and focus on cutting small-diameter trees, Higuera said. Exceptions may include areas where a lot of large-diameter trees are clumped together.

“If I looked at a plan and I saw plans for removing large-diameter trees, that wouldn’t necessarily be cause, in and of itself, to say the project is rubbish,” he said. “I’d want to see where on the landscape that was being proposed, and for what reasons.”


North Bridger logging

A log truck filled with timber descends into Bozeman on Bridger Canyon Drive on Wednesday, Sept. 29, 2021.

Under the new forest plan, National Forest Ecologist Carnwath expects that forest management treatments will be targeted and surgical. The draft plan calls for about 6,000 to 7,500 acres of treatments annually, which is a fraction of 1% of the size of the national forest, he said.

Fuels work will likely occur in the wildland-urban interface — areas where homes and structures meet the national forest boundary. More broadly, managers want to embrace the role of unplanned, natural wildfire on the landscape, Carnwath said.

“The timber harvests, thinning and prescribed burns are the scalpel, and allowing natural, unplanned wildfires to burn in strategic ways is the baseball bat,” he said. “(Unplanned fires) are not going to be as predictable as having controlled thinning operations, but we have the ability to affect a lot more acres.”

Under the new plan, Carnwath doesn’t anticipate that the rate of fuels treatments will increase across the landscape much, if at all. However, some are still concerned about the draft plan’s proposed land designations.

The plan’s management designations include recommended wilderness, backcountry and recreation emphasis areas. Every designation has a list of standards, or mandatory constraints on the kinds of projects and activities that can go on in the area.

The draft plan includes about 126,000 new acres of recommended wilderness in the Crazy, Gallatin, Madison and Pryor mountain ranges. An act of Congress is necessary to officially designate those acres as wilderness.

To Wuerthner, the only management designation in the draft plan with truly protective standards is recommended wilderness. Other designations still allow the Forest Service to approve activities like punching in logging roads or permitting timber harvests for vegetation management purposes, he said.

“A backcountry designation allows them to do what they want to do,” he said. “They use criteria to justify logging on forest lands, even though the trees that are getting cut are big trees that are going to a mill.”

Carnwath said the decision to include a mix of designations reflects two agendas — the agency’s mandate to manage the forest for multiple uses and its all-of-the-above strategy for dealing with climate change and uncertainty.

Not knowing exactly how climate change will affect landscapes means it’s important for the Forest Service to have the flexibility to test different management strategies, Carnwath said.

“We are living through this natural experiment, and while we have some really good science available to us, there’s an amazing amount of uncertainty out there as well. We’re going to have to adapt to change in real time, as it comes,” he said.

When it comes to developing a forest plan, or even a plan for a fuels management project, UM fire ecologist Higuera said it’s important for people to clearly see what the goals are.

In general, treatments that aim to modify fire behavior meet a very specific goal that doesn’t necessarily overlap with extracting trees with value for timber, Higuera said. Ultimately, for people to trust the agency’s work, managers need to propose projects sincerely based on the goals and intentions laid out in the plan.

“If the public doesn’t trust that and thinks they are being deceived, I think there are always some things that can be picked out and poked at,” he said. “There’s a human tendency to not like change. So that, combined with any mistrust between the public and agency can lead to a lot of questioning.”

Whitlock said changes are already underway, and they will likely continue through the middle of the century no matter what managers do. However, reducing greenhouse gas emissions is the best strategy for slowing the changes down.

“If we’re able to reduce greenhouse gas emissions, we can start to flatten the warming curve,” she said. “We just need to be prepared to live in a place where there is more fire and more smoke, and accept that our forests are undergoing change.”

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