Renewing prairies by removing trees

NICOLLET, MINN. - A hawk glided overhead as Pete Schaefer fired up his chainsaw Monday and felled several trees growing among an expanse of prairie grass in a state wildlife area.

The trees were "volunteers" sprouting up on their own on land managed as prairie, offering aerial predators such as hawks and owls a perch to attack ground-nesting birds like pheasants, ducks and songbirds.

While trees usually are embraced everywhere, they're not welcome in prairies, where they can overrun grasslands, dramatically altering the landscape and wildlife habitat. Researchers say bird numbers and nesting success are lower when trees are present.

In Minnesota, state and federal officials have ramped up efforts to restore prairies by removing trees.

"It's a significant problem," said Ken Varland, Department of Natural Resources regional wildlife manager in southwestern Minnesota. "The steepest decline of all our birds in Minnesota and the Midwest is our grassland birds.

"If you don't do it [remove trees], you'll lose more of those birds, including mallards and blue-winged teal."

The DNR is using $1 million in new money from the Outdoor Heritage Fund, generated though the Legacy Amendment, to boost tree removal on state wildlife management areas -- key wildlife habitat popular with hunters. Meanwhile, the U.S. Fish and Wildlife Service has been increasing its tree-removal efforts on federal waterfowl production areas (WPAs), which also provide wildlife habitat and public hunting.

"When I started here in Litchfield and looked at our WPAs, I was appalled at how we had let woody vegetation take over," said Scott Glup, Fish and Wildlife Service wetland district manager. "We've been going gang-busters [removing trees] since then. We're just trying to open up what was true prairie."

Taking some heat

But people often are shocked and angry when they see stands of stately trees cleared.

"They call and ask 'What are you doing?' " said Tom Conroy of the DNR.

Glup said his agency, too, has taken a lot of heat from local residents.

"We made mistakes not involving the public," he said. "Now we send letters to all the landowners within a mile of the area and contact county officials."

Some local conservation clubs planted those trees decades ago, before the detrimental impact of wooded cover in prairies was known.

"It still sticks in the craw of some of those folks [to see the trees removed]," Glup said.

But he said efforts to educate the public have helped. "The word is out." Still, Glup said some people don't like the tree removal.

Count Scott Groen, a farmer and hunter who lives near Willmar, among them.

"I don't buy any of it," he said.

Trees have been removed from both private land and federal land near him, and he says there's less wildlife, including deer and pheasants, on those lands now.

"I don't see where it benefits anything, even nesting pheasants," he said.

Glup said tree removal might affect deer hunting, because without trees, there obviously can be no tree stands.

"But I don't think it impacts the deer population," he said.

Tree removal might affect wild turkeys, he said, which aren't native to the prairie. But the agency isn't removing larger oak woodlands in the transition zone between the former Big Woods region and the prairie, he said.

Most of prairie lost

Most of southwestern Minnesota was barren of trees before European settlement, he noted.

"We've lost 99 percent of our tallgrass prairie," Glup said, and trees have invaded the remnants. Wild fires used to keep trees from growing, but fire was suppressed and settlers planted trees at their homesteads, which provided a seed source for trees to spread.

Both the state and federal agencies use fire to burn prairies, which kills smaller trees and improves grassland quality. But larger trees are removed with chainsaws or heavy equipment. Some are offered to residents for firewood. The Fish and Wildlife Service recently has utilized larger tree clearings as fuel for power plants.

Meanwhile in Nicollet County this week, Schaefer, a DNR wildlife technician, and Jim Hinderman, a DNR laborer, used a chainsaw and shears to remove some trees that had sprouted in the 163-acre wildlife management area that borders Swan Lake, the famed waterfowl lake.

Smaller trees and shrubs such as plum, dogwood and honeysuckle still are planted in shelter belts to provide winter cover for wildlife. But larger trees such as box elder and ash are removed.

"We cut this two or three years ago, but it sprouted back," Schaefer said of the clump of ash trees he sawed. The stumps were again treated with herbicide to prevent regrowth.

"Hopefully, it will work this time," he said.

Doug Smith • dsmith@startribune.com