Michigan’s Landscape Architects – Beavers

The Michigan Nature Association prides itself on protecting habitat for many different species, through the conservation and stewardship at our more than 180 Nature Sanctuaries. But there are times when the needs of one species are counterproductive to the needs of another.

Historically, the American beaver was hunted—nearly to extinction—by fur trading Europeans. Their resurgence across the Midwest has been thanks to conservation efforts, not only for them but also for other species as well.

A beaver swims through a pond. Photo by Lauren Ross.

Beavers are incredible builders, able to construct lodges up to 8 feet wide and 3 feet high, using only their teeth to cut branches and logs, which must then be transported over land and water to the construction site. They are also incredibly effective dam builders—significantly affecting the flow of rivers and streams, which can then flood hundreds of acres of land, creating the ponds and lakes that they require for survival. 

Beaver dam at an MNA Nature Sanctuary. Photo by Andrew Bacon.

This keystone species are the architects of wetlands and pools in riparian ecosystems—the area between land and rivers and streams. Their damming and wetland creation is invaluable for a wide diversity of wetland birds, herptiles, and insects. Where beavers are allowed to operate in their natural capacity, there are tremendous benefits for wildlife and water quality within the riparian corridor.

However, in sensitive habitats like the prairie fens, found at a particular MNA Nature Sanctuary in Oakland County, these habitat architects can actually have a destructive effect by flooding and killing these rare plant communities and the rare species which occur within them. One of the two creeks that flow through the sanctuary has been dammed by beavers for over a decade and has enlarged the lake on the eastern side of the sanctuary. If left alone, the dams could eventually flood the fen and create an emergent marsh habitat comprised primarily of cattail, pond-lilies, and other wetland species. And though this type of habitat is common across the state, the transition in this particular location is not ideal.

Prairie fen (left) photo by Dave Cuthrell, Emergent marsh (right) photo by Joshua Cohen courtesy MNFI.

The prairie fen at this sanctuary is one of the last places on earth where the federally endangered Poweshiek skipperling makes its home. The loss of occupied prairie fen habitat at this sanctuary would have a catastrophic effect on the global population of these tiny butterflies.

After consulting with several conservation scientists about the issue, MNA conservation staff determined that the beaver activity constitutes a grave threat to the rare species found within the prairie fen, and that sanctuary management would include curtailing the flooding in order to maintain access to the sanctuary. This approach—prioritizing the needs of more rare species over more abundant ones—is commonly taken by conservation organizations at both the local and national levels.

Humans, like beavers, are capable of altering their surroundings in ways that most other species are not. Like the beaver and the butterfly which cannot know that in this place is nearly all that remains of the Poweshiek skipperling, humans too have a limited amount of knowledge to guide our activities. It is, however, with conscientious and scientific thought. Nature forces us to make some very difficult decisions at times—so as we work to protect Michigan nature for everyone, we must also recognize when one species requires more of our efforts than another.