Whitetail deer diminish diversity of Minnesota’s northern forests

Paul Ojanen is a Northeastern Minnesota native who has worked in conservation. His graduate research was on the impacts of earthworms on Sugar maple forests in Wisconsin’s Chequamegon-Nicolet National Forest.

Sugar maple stand near Grand Portage, free of deer browsing. Photo by Paul Ojanen

If you ask for a symbol of Minnesota’s northern forests, many people will mention the white-tailed deer. It is a favorite among hunters, and its beauty and grace are a familiar part of the landscape.

But it may surprise people to know that white-tailed deer were not common or even present in much of northern Minnesota until relatively recently. The extremely cold winters and vast areas of mature forest with little undergrowth that once characterized the region made poor habitat for deer, according to researchers. In fact, in a 2000 article published Biological Conservation, Cornett, Frelich, and others noted that “deer may have been completely absent from northern Minnesota until the early 1900s.”

Instead, caribou, elk, and moose wandered the expanses of forest and bog. A few caribou even made themselves at home near Grand Marais in the 1980s.

But the big herds of caribou were considered extirpated from Minnesota in the 1940s, possibly due to logging and forest fires, increased hunting and predation, and brainworm contracted from an expanding deer population. Elk had disappeared by the early 1900s due to excessive hunting in the 1800s, according to the Minnesota DNR. And the state is currently engaged in a multi-year research effort to try to determine why the moose population in northeastern Minnesota has plummeted.

It took roads and agriculture for deer to invade the region. Heavy hunting pressure during logging and early non-native settlement prevented their populations from growing and it was only well into the mid-twentieth century that their numbers became significant. Humans made the habitat for the whitetail, and the animals adapted well to the roads, fields and suburban areas we created.

A hardwood forest dramatically impacted by deer browsing. Photo by Paul Ojanen

In turn, the deer have impacted our forests, as they voraciously browse many tree species, preventing their growth. Heavy browsing has nearly eliminated some species, while others require protection or management just to reproduce existing trees. White and other pines, along with white cedar, Canada yew, sugar maple and oaks are all on the white-tail’s menu. As one forester said, “I am sick of feeding deer. If I plant, I plant white spruce only. It is the one thing they won’t eat.”

Travelers up the North Shore of Lake Superior today can readily see the impacts of deer browsing, both in the species of trees that are able to regenerate and in the understory plants.

Along Lake Superior's North Shore, birch are dying and few species withstand heavy deer browsing. Photo by Spring beauty. Photo by Molly Thompson

Along Lake Superior’s North Shore, birch are dying and few species can withstand heavy deer browsing. Photo by Spring beauty. Photo by Molly Thompson

In the winter, deer congregate in large numbers below the rocky heights that rise above the lakeshore. Decades of heavy browsing prevented natural regeneration of all except inedible species such as spruce. As the once vigorous paper birch forests created by logging and fires a century ago have died off due to age and drought, the forests near Highway 61 now appear as “skeleton” forests, with open areas, small trees and brush.

The one tree able to regenerate naturally is the white spruce, a slow-growing evergreen that now dots the understory. Sugar maple forests also suffer, the once thriving young trees eaten to the ground, leaving a swath of grass and sedge.

Nodding trillium. Photo by Paul Ojanen

Farther inland, where snow is deeper, winters are colder, and wolves prowl, some areas remain free from deer browsing. These are some of the last remaining high quality hardwood forests in the state. They are home to a generous diversity of plants. Dominated by sugar maples and basswood, their understories are dense with seedling and saplings. The early spring sunlight before leaf-out is the time when wildflowers, especially the “spring ephemerals,” open their flowers to the sky. Spring beauty, Dutchman’s breeches, violets and trilliums rise from the leaf litter, sometimes creating floral carpets rich in color. Farther north along the shore, one can find large clones of Canada yew, which for a botanist is akin to seeing an extinct life-form, so rare is it anywhere that deer exist. As leaf-out progresses, other species flower, but gradually the big trees capture most of the sun, and the light-filled forest with its colorful carpet of wildflowers turns to dense shade and deep green.

Minnesota has moved to protect some of these remnants of once vibrant ecosystems as Scientific and Natural Areas. Hovland Woods SNA features old white pine and white spruce which provide habitat for rare lichens and nesting eagles. Spring Beauty SNA on the northern edge of the range of these hardwood forests, is home to several protected plant species.

Spring beauty. Photo by Paul Ojanen

People are also working to restore native trees and associated plant communities along the North Shore. Sugarloaf: The North Shore Stewardship Association and The North Shore Forest Collaborative are encouraging coordination among federal, state, and local governments and private landowners in voluntary projects to address issues such as dying birches, over-browsing, and invasive plants. A common strategy is to plant sensitive seedlings and protect them with “exclosures,” fencing to keep out deer. The ambitious goal is to “revitalize and maintain a healthy and functioning ecosystem along the North Shore of Lake Superior.”

Minnesotans will probably always relish seeing deer, but landowners and resource managers are reaching for a balance that preserves the rich diversity of the region.

Suggested reading:

Share this:

About Paul Ojanen