Deep in northern Michigan’s Huron-Manistee National Forest, the air reverberates with the sound of a tree harvester picking up fully grown jack-pines out of the ground like toothpicks.

Once the trees are lifted, the machine, known as a forwarder, slices the tree into logs in less than a minute.

“It cuts the trees to a certain length that meets our technical specification,” said Matt Bonnau, a harvest inspector for the Huron-Manistee. “Zips them, de-barks them, de-limbs them, and then it cuts it to length.”

This is just one of hundreds of timber harvests that take place all across the Midwest in places like the Hoosier, Shawnee and Mark Twain National Forests. These trees, ranging from jack-pines in northern Michigan, to cedar trees in southern Missouri, go on to sawmills where they will become various woods products or ground into pulp.

In fiscal year 2023, national forests in Michigan, Wisconsin, Missouri, Indiana and Illinois sold a combined $32 million worth of convertible wood products.

While how many trees should be harvested on national forests has been a long debate — now the discussion centers around climate change. Several estimates show that forests capture roughly 13% of the nation’s carbon emissions each year. Yet conservationists and Forest Service officials don’t always see eye-to-eye on a path forward to maximize forest health as a natural way of snatching up carbon.

Which trees do the best job of storing carbon?

Every 10 years, the U.S. Forest Service files a report on the state and future of national forests — this year’s study included 50-year carbon projections.

The report concludes that climate-induced stress will lead older trees to release more carbon dioxide than younger ones over the next five decades.

“As climate changes more rapidly, many forests will experience chronic stress and be more susceptible to disturbances from storms, insects, and fire,” wrote a Forest Service spokesperson in an email to Harvest Public Media.

“Reduced growth, which means less carbon capture, increased disturbance and mortality, which means more carbon release or emission, means that the carbon sink (absorbing more carbon than it releases) in many forests will continue to be weaker without adaptive management.”

Although the report doesn’t prescribe any management policies, Carolyn Ramirez, a staff scientist at the Natural Resources Defense Council in Chicago, said it’s likely to be influential on Forest Service directives. The report’s carbon outlook could lead to more logging, she said, which in turn will hurt forests’ ability to capture more carbon and harm climate security.

“The rate of that carbon sequestration, the rate of that absorption, still remains really high for older stands even if it's not accelerating as fast as it once was when it was younger,” Ramirez said. “If you cut down a really old tree, we will not recover that carbon storage in our lifetime.”

According to the Forest Service, mature and old-growth forests store more carbon than younger forests, but typically they are not stronger at retaining that carbon when compared to younger forests.

The Forest Service also says that older trees are no more resilient to climate-caused stress than younger ones, a conclusion conservationists dispute.

“When forests reach maturity, on federal lands, the knee-jerk reaction is to cut them down, they've reached the peak of their value,” said Zack Porter, executive director of the group Standing Trees, an organization that works to protect native forests in the northeastern United States.

Porter says forests across the Midwest and Northeast haven’t been allowed to reach their full maturity and climate-capture value because the country has been caught in a logging cycle for centuries.

“And are we willing to make changes based on what the science is telling us, which is that forests function best when left alone,” Porter said.

Porter cited a recent study co-authored by Richard Birdsey, the Forest Service’s former manager of the Northern Global Change Research Program, as evidence for leaving forests alone to grow old.

“We found that middle-aged eastern U.S. forests could continue to accumulate carbon for many decades or several centuries in the absence of harvesting, with relatively low risk of natural disturbances,” the abstract of the study reads.

Forest health vs. mature growth

Thinning forests is important for reducing the risk of wildfires, which are huge carbon emitters, according to the Forest Service. It's also about promoting forests’ overall health.

Forest Service silviculturist Keith Konen said they thinned a particular area of the Huron-Manistee National Forest a few years ago to give trees more space and reduce stress.

“What that does is focus available resources such as light, water, (and) nutrients to the residual remaining trees that are left there,” Konen said. “And that reduces competition. It increases growth.”

But environmentalists are fighting some logging efforts in the Midwest.

Recently, the Environmental Law and Policy Center sent a letter to Forest Service officials urging them to halt the logging of 12,000 acres of mature forest known as the Fourmile Vegetation Project in the Chequamegon Nicolet National Forest in northern Wisconsin. The ELPC argues that several policy changes made under the Biden Administration should halt the logging.

“They're harming our climate security, and they're increasing climate risks by reducing our stores of carbon,” said Andy Olsen, a senior policy advocate with the ELPC based in Madison, Wisconsin.

“What they're trying to do is to reset the forest age in these areas from more mature forests that could ultimately grow into old-growth forests and evolve. Instead, they're knocking them back to a younger state.”

The Forest Service said in an email that both the Department of Agriculture and U.S. Department of the Interior’s Bureau of Land Management have developed mature and old-growth forest definitions and a national inventory of this kind of land following the signing of President Biden’s Executive Order 14072 on Earth Day 2022.

The email also said there can be a lot of misconceptions surrounding the Fourmile project and the differences between mature and old-growth forests. “Vegetation management was identified as the main focus,” reads the Forest Service’s environmental assessment of the Fourmile project. Other goals the Forest Service laid out for the project include improving tree species diversity, obtaining data for long-term research and improving wildlife habitat.

In the long run, others argue the market would offset whatever decisions the Forest Service ultimately makes.

Should less logging happen in national forests, more trees would be cut down in other forests, according to Chad Papa, a Ph.D. candidate in the Department of Forestry at Michigan State University and research assistant in the university's Forest Carbon and Climate Program. Data from the National Association of State Foresters estimates over 50% of the nation’s forests are privately owned.

“By not harvesting someplace, you're most likely just pushing that harvest off to another place instead,” Papa said. “And so, the net effect is essentially the same."

Papa said the Forest Service and conservationists would likely agree more than they think about forest health. Both understand the critical role these lands will play as a climate change solution in the coming decades.

“It's just looking at the same coin from two different sides, in a lot of ways,” Papa said.