Park naturalists prescribe controlled burns and deer culls to control invasive species

On a cloudy, 40-degree day in late November, 12 men in hunter's orange and camouflage green enjoyed a catered meal of barbecue beef at Addison Oaks County Park in northern Oakland County. Provided by Oakland County Parks & Recreation, the lunch was a token of gratitude for the service these men were about to deliver: helping parks staff reduce the local deer herd.

The deer cull was part of an annual lottery-based Managed Hunts  program run by the suburban park system as part of the Michigan Department of Natural Resources' Deer Management Assistance permit program. The objective of the program is twofold: to protect the ecological integrity of natural communities and to promote the health of wildlife. Only antlerless deer were shot that November day—no bucks. And hungry people benefited, as all venison gleaned from the hunt was donated to area food pantries.

By combining deer management with lower-cost invasive management techniques like prescribed burns, the park system stretches limited dollars for ecosystem management, according to Brittany Bird, a natural resources planner with Oakland County Parks and Recreation. That's important when you have thousands of acres of suburban park land to manage.

"We have 6,800 acres, and about 70 percent of that is undeveloped," says Bird. "That's a lot of acreage to be managing. We have a small crew of five field technicians, four of which are seasonal. Burning and deer hunts are some of the more cost-effective measures that we can take to help with ecosystem restoration. They can have widespread effects for a relatively low dollar investment per acre."

Landscape fragmentation with 'cascading effects'

Because it is the second-most populous county in Michigan, Oakland County faces a myriad of threats to its natural resources. These come not just from invasive species, but by encroaching urbanization that fragments natural areas. And because deer thrive in "edge habitats"—the borders between nature and suburbia—the area's deer population has skyrocketed in recent years.

According to a USDA report, a deer-impacted forest may look deceptively healthy. But saplings, shrubs, bushes, grasses and flowers can easily succumb to overbrowsing. At Addison Oaks, deer munch on native plants and grasses, clearing the way for invasive species like glossy buckthorn to take root.

Bird's goal is to allow native grasses and associated prairie plants to re-establish a prairie habitat in Addison Oaks, but an overabundance of deer eating away at those plants undermines her work. The endgame is to rebuild functional ecosystems that support all of the plants, animals, and natural processes that are supposed to be there.

"Everything is connected," says Bird. "If you have invasive plants that were not once part of these ecosystems, that removes the food source, the nesting materials, the things that the wildlife in the area depend upon. You then have cascading effects. Everything from your pollinator base to your birds to your small and large mammals can be negatively impacted by the lack of proper plants for nutrition and habitat that they’re used to."

As an example, Bird points to the emerald ash borer, an invasive insect that decimated ash trees in Michigan in the last decade. This in turn led to a decline in some bird species that depended on ash trees for habitat.

Unlike the emerald ash borer, deer are native species. But when too many deer roam a park, problems will occur.

Controversy over culling

Although prescribed fires and scheduled deer culls provide cost-effective ways for Oakland County to manage invasive species in its parks, some groups oppose deer culling on public land.

Recently, the city of Ann Arbor's plan to reduce the number of deer in city parks by hiring sharpshooters drew public ire. Some groups and citizens felt that killing deer is unethical and a waste of money. Others saw a need to manage the herd to promote ecological stability.

Similar concerns have arisen in Oakland County, says Bird, but she notes that parks personnel have been able to largely assuage public concerns by being proactive in communicating the purpose and benefit of the culls.

"Obviously, you are harvesting animals, and a lot of people really enjoy seeing wildlife, and we do too," she says. "But we want to be providing the correct habitat for those animals. We want to be managing population densities such that they're not getting to a point where individual deer suffer from things like disease and starvation."

Burning for posterity

The second part of Bird's strategy, prescriptive burns, has also been the subject of concern, primarily by neighbors and local officials.

"When we started our burn program, we did a lot of public outreach, a lot of postcard mailing to neighbors, and communication with fire department officials and township supervisors." says Bird. "There was definitely some apprehension the first couple seasons. Once we were able to put the fire on the ground and demonstrate that we can do it in a safe manner and have positive impacts on the natural areas, we've gained a lot of support for the program."

The burns work to kill woody invasive shrubs like buckthorn and autumn olive and are a natural process in prairie ecosystems. Fire suppression by humans is one reason why prairies are so rare today.

Prescribed burns and deer kills are a part of an overall natural resources management approach, which comprises not only invasive species control, but planting of new trees and native foliage, wildlife management, land conservation, and more.

Since the managed hunt program has been put in place, deer population densities in Oakland County parks have been reduced. That, combined with prescribed fire, has resulted in a rebound in native prairie species in some areas of the parks.

"We're just now getting to a point that we're seeing what possibly can come out of the seed bank," says Bird. In some cases, those seeds may grow into plants that haven't been seen in the area for decades, if not a century. "It's like bringing the past back to life."

This story is a part of a statewide Invasive Species Community Impact Series. Support for this series is provided by the Michigan Department of Natural Resources.