A New Focus on Old Growth

On a sunny fall afternoon, I drive west from Minneapolis, past the strip malls and cul-de-sacs, until I come to a church parking lot. Tucked into the back corner are a few wooden benches and a brown sign with the telltale yellow lettering: “Wolsfeld Woods Scientific and Natural Area.”

A small dirt trail leads up into the trees. As I climb through the opening, the modern world recedes behind me and another one opens.

Wolsfeld Woods is one of the few remaining patches of “Big Woods” left in Minnesota. These maple-basswood forests once covered 1.3 million acres between the Mississippi and Minnesota rivers. Most of that is gone now, but thanks to the Wolsfeld family’s syrup business, this 165-acre patch was spared.

In 1978, Wolsfeld Woods became one of Minnesota’s first Scientific and Natural Areas, and in 2024 it became one of Minnesota’s first forests inducted into the Old Growth Forest Network, a national organization that raises awareness about the last parcels of ancient forest left standing across America.

“We’re working around the country to identify the best example of the oldest forest in every county,” says Nick Sanchez, manager of the network. “We see them as a gateway to pull people into caring about the environment and conservation. These are some of the most inspiring places you can visit.”

Portals into the Past. At Wolsfeld Woods, the trees stretch up over 100 feet, creating a high canopy that makes the forest feel like a cathedral. When trees are leafed out, Big Woods tree cover is so dense that only 1 percent of the sunlight reaches the forest floor. On this fall day, however, this patch feels airy and bright.

Old growth forests are islands in a sea of change. They are portals into the past. Walking through one feels like time travel. Before Europeans settled here, 51 percent of Minnesota’s forests were made up of old growth. Now there is much less.

“In the Great Lakes region,” says Sanchez, “it’s estimated that less than 1 percent of the pre-European settlement forest remains intact.”
“What about the Boundary Waters?” I ask.

“That’s why it’s 1 percent,” Sanchez says.

The forests in the Old Growth Forest Network are but a portion of the state’s designated old growth. The Minnesota Department of Natural Resources estimates that state lands hold 48,276 acres of old growth. That doesn’t include any county or federal lands, including the Boundary Waters, which has over 400,000 acres of old growth among its 1.1 million acres.

The state has some of the best potential in the region for visiting an old growth forest. According to Sanchez, Wisconsin has no large tracts of old growth, while Iowa, South Dakota, and North Dakota currently have no entries in the Old Growth Forest Network.

Minnesota’s most famous stand of old growth is the Lost 40 Scientific and Natural Area. This 144-acre forest was set aside by accident in 1882 due to a surveying error. It was 80 years before anyone noticed, and then the decision was made to preserve it. The Lost 40 has never been logged; some of its red and white pines started growing in the 1700s.

Eight in the State. In October 2023, a group of DNR staff, along with local students and residents, hiked into the Lost 40 to formally welcome it into the Old Growth Forest Network as Minnesota’s first such site.

The next day, some in the group traveled southwest to the Itasca Wilderness Sanctuary SNA, which is home to a stand of red and white pine that’s over 200 years old, to make it the second forest to join the network. (Itasca State Park, where the SNA is located, holds 6,511 acres of old growth forest, including a stand of red pine that’s over 300 years old—among the oldest forests in the state alongside the Lost 40.)

Since then, six other Minnesota forests, all of them in SNAs or state parks, have been added to the network. In 2024, Wolsfeld Woods SNA, Townsend Woods SNA, and Sakatah Lake State Park joined, adding three stands of Big Woods. Then in 2025, Tettegouche State Park, Lutsen SNA, and George H. Crosby Manitou State Park were inducted, bringing the total to eight.

Tettegouche State Park, for example, has numerous stands of old growth where logging was difficult. Most are deep in the park, but one such stand sits right along the Superior Hiking Trail, near the “drainpipe” stairs. According to park naturalist Kurt Mead, these old growth sections feel different than younger forests.

“A lot of the woods up here are thick and brushy and tough to walk through,” he says. “But these old growth areas with the heavy canopy tend to be more open. And the trees are quite large. They’re two or three arm spans around. Some of these yellow birch and sugar maples were growing and healthy trees before the Declaration of Independence was signed. That’s just a powerful thing for me.”

Many Types of Old Growth. The DNR defines old growth as “forests that have developed over a long period of time, essentially free from catastrophic disturbances.”

“Basically, old growth forests are in the late stages of forest succession,” says Jamie Mosel, DNR forest ecology and policy program consultant. “Forests move through young, mature, old, and then old growth stages. In their oldest growth stage they have a lot of unique characteristics that they achieve over time. They become more structurally complex. Sometimes people call them ‘decadent.’”

Different trees have different lifespans, hence different definitions of “old.” White spruce forests are considered old at 90 years. Hardwood forests, like maple, ash, and oak, are more like 120 years. And northern white cedar can grow to be more than 600 years old.

“When people think of old growth, the pine forest comes to mind,” says Kelly Randall, statewide outreach consultant for the DNR’s Scientific and Natural Areas. “But Minnesota has lots of other types of old growth. There are floodplain forests with cottonwoods and silver maple. There are oak and aspen forests. And there are lowland conifer forests found in peatlands. All these forest types can be old growth.”

In fact, the DNR is currently considering 40,816 acres of lowland conifer forests on state lands for old growth designation. Made up of tamarack, black spruce, and northern white cedar, they don’t look like stereotypical old growth, even though they are. In Minnesota, some lowland conifer forests have been estimated at 224, 234, and 268 years old. (One of the oldest tamarack trees ever recorded had lived for 335 years.)

“The species growing in those lowland conditions tend to not be as large because the conditions can be really poorly drained, acidic, and harsh,” Mosel says. “They’re basically growing as little as possible each year and hanging on, so they have tiny, dense growth rings.”

One study on tamarack regeneration found an 82-year-old tree that was just 2½ inches in diameter.

The designation of lowland conifer stands could substantially increase the amount of old growth on state lands.

Hiding on the Landscape. There’s probably even more old growth out there. In Michigan, the Old Growth Forest Network recently welcomed a 70-acre forest filled with 350-year-old trees in metro Detroit. Elsewhere they found a patch “hiding in plain sight” next to a hayfield.

“I no longer say you won’t find them here or there,” says Sanchez, “because they are in surprising places. I’d be willing to bet there are old growth oak woodlands that are out there in Iowa. These places are often hiding out on the landscape.” (If you know of such a place, you can nominate it on the Old Growth Forest Network website.)

In addition to finding more “Lost 40s” around the country, he says they also want to encourage the expansion of current old growth stands, letting the forests around them age into the later stages, as a way to help ensure their survival.

Many old growth parcels are on the smaller side, he says, “and those are pretty vulnerable when it comes to things like fire and windstorms and climate change.”

See What Remains. The warming world is a real concern for old growth forests. While their diversity, complexity, and relatively undisturbed character can make them more resistant to invasive species, they can be vulnerable for a number of reasons, says Mosel. “One is that many of these trees grew up under a past climate. The climate today is already very different from the conditions they’re adapted to. That makes them vulnerable despite their gift of longevity.”

This makes it all the more urgent not only to save what’s left, but also to get out and see what remains. The DNR and the Old Growth Forest Network want people to experience the state’s oldest forests.

“We want to get people out visiting these sites,” says Mosel. “It’s just this really beautiful resource and legacy that we have. Pretty much everyone loves old growth.” 
 

 Ancient Forests

Eight Minnesota woodlands have been inducted into the Old Growth Forest Network, a national group that raises awareness about old growth. Minnesota also has more than 45,000 acres of additional old growth on state lands and more than 400,000 acres in the Boundary Waters Canoe Area Wilderness. The eight woodlands are: 

• George H. Crosby Manitou State Park 

• Lutsen SNA

• Tettegouche State Park

• Itasca Wilderness Sanctuary SNA

• Lost 40 SNA

• Wolsfeld Woods Scientific and Natural Area

• Townsend Woods Scientific and Natural Area

• Sakatah Lake State Park Scientific and Natural Area