Anderson: In Minnesota and everywhere, trees threaten grasslands and the pheasants they support

Cory Netland is a Department of Natural Resources area wildlife supervisor working out of New London, Minn. — not too far from where he grew up.

Like the state’s other 80,000 or so pheasant hunters, Netland is eagerly anticipating the Oct. 12 opening of the 2024 ringneck season.

And while Netland knows that wingshooters and their dogs who tromp the six west-central Minnesota counties he oversees will flush reasonable numbers of the world’s most florid game bird, he also knows everything about that part of the state is different than when he was a kid.

Jack rabbits, for instance, are mostly gone. Badgers, too. Also songbirds such as meadowlarks and bobolinks.

And the Hungarian partridge Netland once hunted on his grandparents’ farm?

They’re still a game bird in Minnesota. But just like the prairie chickens that once were plentiful here, good luck finding one.

The disappearance of these and other wildlife species have followed the loss of more than 90% of Minnesota grasslands, which have been replaced by a monoculture of corn and soybeans.

Now, an equally ominous threat is poised to gobble up the state’s remaining grasslands and the birds and other wildlife they support.

“Trees are a clear and present threat to all of our grasslands,’’ Netland said. “In my management area, I haven’t planted a tree for at least 10 years. Instead, I spend most of my time taking trees down, using all of the tools I have to do it. Fire. Chemicals. And mechanical means, meaning skid steers, chain saws and a strong back.’’

Netland isn’t alone.

“A lot of people don’t associate trees with being bad for the environment,’’ said Scott Glup, project leader of the Litchfield (Minn.) Wetland Management District of the U.S. Fish and Wildlife Service. “But across southern Minnesota we take out tens of thousands of trees each year.’’

“Tree creep’' began centuries ago when white settlers replaced Native Americans on the landscape.

Unlike Indigenous people who used fire to regenerate grasslands to attract bison and also to keep mosquitoes and other unwanted vermin at bay, early settlers — and the generations that followed — suppressed fire.

Additionally, along with their hopes and dreams, they brought trees.

“Vast portions of the nation were once covered by tall grass prairies,’’ said Dirac Twidwell, a University of Nebraska professor whose specialty is rangeland ecology. “What most people don’t realize is that a third of those prairies burned every year.’’

The fires not only enriched the grasses for bison, they prevented tree growth.

In the centuries since, as eastern redcedar in particular, but also cottonwoods, box elders and Siberian elms, among other trees, have flourished on former grasslands, the American countryside has been changed in ways that only recently are being fully understood.

Not only has wildlife been lost, experts say, so have the carbon sequestration qualities of grasslands. And on the Great Plains and in the Western U.S., critical food sources for livestock have gone the way of the passenger pigeon. Twidwell estimates, for example, that trees and shrubs that have invaded the Flint Hills of Kansas in the past three decades have reduced forage grown in the region by about 1 billion pounds.

Aerial photos archived by the University of Minnesota show how dramatically some parts of the state have changed, Netland said.

“The photos show the presence of trees today where trees didn’t exist before, even as recently as the 1980s,’’ he said. “The changes are even more dramatic if you look at photos dating to 1938.’’

Twidwell, the Nebraska professor, said that nationally as much grassland is being lost each year to trees — woody encroachment, is the scientific term — as to agriculture.

“South Dakota today, with the encroachment there especially of eastern redcedar, looks like Nebraska did a few decades ago, and Nebraska looks like Kansas did a few decades before that,’’ he said. “In Minnesota, where the best lands are already in agriculture, trees will take over the rest unless those lands are managed.’’

Fighting trees isn’t cheap. In Minnesota alone, Pheasants Forever (PF) has spent more than $5 million in recent years to combat woody encroachment.

“The scientific community has known for a long time the effects of woody encroachment on grasslands, grassland habitat and grassland wildlife,’’ said Becca Kludt, a PF biologist who is the group’s land restoration manager in Minnesota. “But it’s only been in the past few years that public perception has changed about the importance of removing encroaching trees and managing the lands afterward to prevent the trees from coming back.’’

Though various studies have shown that pheasant nesting success and survival increase when trees are removed, some hunters cling to the mistaken belief that shelter belts and other woody cover substantially benefit these and other birds.

“With pheasants, nesting cover is the limiting factor,’’ Netland said. “Year to year, the number of pheasants we have depends on their nesting success, and you can’t have nesting success without grasslands. In some cases trees can provide winter cover. But you need to be very careful where you allow them to exist.’’

Glup agrees.

“We have private lands in our working area where the cedars are so thick you can’t walk through them,’’ he said. “You have to crawl. And nothing — no grass, nothing — grows beneath them.’’

Worst-case scenarios include those where mature trees have taken hold, replacing grasslands. Using government funding, as well as grants from the Legacy Act’s Outdoor Heritage Fund, the DNR, the Fish and Wildlife Service and PF contract to have the trees removed and burned.

Saplings and other younger trees can sometimes be pulled or killed by prescribed fires.

“We’ve also had Boy Scouts, master naturalists and other volunteers help remove trees,’’ Glup said.

Said Netland:

“Keeping trees out of our remaining grasslands is never ending work. But it has to be done.’’