From Overgrowth to Renewal

A FOREST MADE FOR FIRE

The fire burns close to the ground at low heat with short flames. It consumes deep needle litter and dried vegetation, removing excess fuel that, under the wrong conditions, could stoke a destructive blaze.

According to Mike Schaedel, Western Montana forest restoration director with The Nature Conservancy, dry forest ecosystems like these, which grow across 150 million acres of the Western U.S., have evolved to depend on fire. For example, seeds from ponderosa pine and western larch use the bare soil created by burns to germinate.

“If fire wasn’t important in these landscapes, that wouldn’t be an adaptation,” Schaedel says.

Western dry forests have had a close relationship with fire over millennia.

When European settlers came to western North America, they found park-like dry forest landscapes—grand giants spaced apart with grasses underneath.

“That wasn’t an accident,” Schaedel says. “People have been using fire to carefully maintain those forests for generations, using their own traditional ecological knowledge and science.”

Western dry forests became dependent on flames, which cleared excess growth and brought about life and regeneration. But today, these ecosystems have become overgrown, following policies and management that removed fire from the landscape by preventing Indigenous burning and extinguishing natural fire. As a result, wildfires are now behaving in unpredictable ways and burning larger swaths of forest at greater severity.

RESTORING HEALTHIER FORESTS

Together, ecological thinning and burning can transform a forest’s trajectory and return the land to a healthier, more resilient condition. Studies have shown thinning or burning alone can reduce wildfire severity in dry forests by up to 62%. When used in combination, that number increases to 72%.

TNC experts and partners work with landowners to identify dense sections of forest for treatment. They focus on landscapes where high-severity fire could pose the greatest risk—areas near communities or important ecological resources, like large trees, old-growth forests or threatened wildlife habitat.

They aim to restore a forest structure with greater resilience to severe wildfire and climate change, one that mimics conditions from hundreds of years ago, when low-intensity fire regularly managed forests.

When thinning, experts try to achieve a clumpy spatial pattern, in which some trees are grouped together while others are individually spaced and broken up by meadows and gaps. Fire-adapted species, like ponderosa pine and Western larch, as well as the biggest, healthiest trees, are left to flourish, along with some younger trees, creating a diverse forest structure.

“We want to see a wide range of tree sizes and ages—old intermixed with young, and even some dead trees, for the benefit of wildlife,” says Rob Addington, TNC’s Colorado forest and fire program director. “And we want to see meadows interspersed throughout the forest—in some cases, some pretty large meadows with vibrant plant communities.”

In many ways, restoration begins not with the forest canopy, but with the forest floor. Prescribed burns and other low-intensity fires help recycle nutrients, spurring regrowth.

Addington says that often the goal of restoration is to open up the forest and stimulate the grasses, forbs and other plants that make up ground cover. This, in turn, encourages greater diversity, supporting a more resilient ecosystem.

“A lot of diversity originates in the ground cover and the understory plant community,” he says. “The diversity there affects the diversity of the insect community, which can then affect the diversity of other wildlife, like the songbird population. You get these trophic cascades that go all the way through the system.”

SPRING OF REGENERATION

Just months after a prescribed burn, the forest is already transforming. Out of the soot and scorch, below the healthy, newly spaced conifers, young grasses, forbs and sedges emerge, and recovery begins.

In the spring, lupine send knee-high blooms of purple and blue up into the air, mingling with yellow splashes of sunflower-like balsamroot and arnica, as well as multicolored hues of paintbrush flowers. In forests with wetter meadows, violet and lilac tones of blue camas, a culturally significant food for Indigenous Peoples, dot open spaces.

“Following either thinning or burning, it often doesn’t look great, but when you return a few months later or less, what you see in terms of what's coming back is really astounding,” Addington says.

By the beginning of summer, grasses and shrubs like mountain mahogany, wax currant and antelope bitterbrush are putting out healthy shoots and branches.

The verdant growth and new openings in the forest created by the restoration attract mule deer and elk, who seek out the nutrient-rich plants. Birds, like hairy woodpeckers, northern goshawk and Mexican spotted owls are also attracted to burn sites.

“A lot of birds key into fires—whether it’s a woodpecker that’s going to search for insects after fire, or whether it’s a hawk zooming over because there’s nothing for mice or voles to hide in,” Ward says. “They’ll start hunting at those locations, hoping for a high success rate. So wildlife return almost immediately.”

In Montana, dusky grouse, large fowl with dark feathers and purple-red air sacks on their necks, emerge to mate.

“They seem to just pop out of the woodwork, I’ve seen it a couple of times now in stands we’ve thinned and burned,” Schaedel says.

THE CYCLE OF RESTORATION

The flush of new life and regrowth of vibrant flowers and understory plants lasts about two to three years. In a few years, seedlings from fire-adapted trees like ponderosa pine, germinated by soils exposed by the return of fire, will emerge.

In five years, those seedlings will develop into saplings. Shrubs will grow large and robust, and hearty grasses will continue to develop.

As the years roll on, dried vegetation will begin to accumulate once more, as branches shed, trees live and die, and needles begin to pile. Some of the young saplings will begin to crowd the more mature trees.

“As you get further away from when that fire happened, the cycle starts again where you see more trees coming in,” Ward says. “And then over time, you’re going to see this reduced diversity and reduced use by wildlife.”

Experts are finding that forests need to be burned about every 15 years to restart this cycle and remain healthy.

On some sites, fire may occur on its own even earlier. And when that happens, in areas that have been treated, the fire will drop out of the canopy, down to the ground, where it will likely burn low, without inflicting significant damage on the large, older trees.

And the cycle continues. The understory plants and wildlife return, the site matures and low-intensity fire returns in some shape or form. Over and over again.

“I always look at restoration as a process or a journey, not an event,” Addington says. “You’re continually improving and continually increasing the health and the resilience of the system.”

Humans have always been critical to maintaining that cycle, which in turn reduces severe fire risk and protects important ecological, social and economic resources.

“Everything gets disturbed,” Ward says. “And that's how the system evolved. Humans are now a disturbance, and we are part of the restoration effort.”