Beaver: Creator or Destroyer?

Beavers, by building dams and lodges, are masters at creating the surroundings they need for their survival. Studies indicate that beaver may have had an even larger role than previously believed in the creation of some of the most fertile lands in North America. Lowlands, previously prehistoric lakebeds, may actually have been marshes created by centuries of beaver activity.

Pre-historically, beaver ranged through most of North America, from the northern tundra to what is now northern Mexico. Virtually anywhere water and trees existed, so did the beaver. The continental beaver population, estimated at 60 million to 400 million animals, was dramatically reduced by trapping during the fur trade.

Settlement and cultivation of the beaver's wetland habitat further reduced their population. Today, with relative freedom from large-scale trapping and fewer natural predators, beaver populations are increasing. They are returning to streams and wetlands from which they have been absent for decades, and new generations of humans are learning first hand about the beaver's ability to modify waterways.

To protect their lodge and food supply, beavers need water deep enough not to freeze. A stream with poplar near the banks is ideal. Poplar bark is food and the barked limbs and trunks provide raw material for dam construction.

The dam grows, and with it grows the area of relatively calm water behind it - a pond which is talking the first steps in developing into a marsh, and ultimately into highly fertile soil. Sedimentation within the pond increases as soon as the beaver begin their work and the stream velocity slows. The amount of organic material in the water and on the bottom of the pond increases. So does the quantity of nutrients in the pond and along its banks.

Even the type of vegetation in the riparian area changes. Poplar, the beavers' favourite food and building source, are typically cut down from the immediate shoreline. This encourages sprouting of poplar saplings. Eventually, though, the beaver exhausted the available food supply including new sprouts and saplings and move on.

When the beaver move to a more appealing location because of the food supply is becoming distant or the pond is becoming shallow, the poplar rebound. The soil and brush conditions are ideal for rapid growth of new stands of poplar. The new stands mature, the beaver return, and the cycle continues, with more fertile area created each time.

Pest or Benefactor?

As the population increases, beaver are earning a reputation as a pest. More beaver need more lodges and more dams, so they cut more trees and flood more land. That makes them a nuisance in the eyes of landowners who see wetlands expanding over land they have previously used for annual crops or forages. Swaths have been used for dam building, and roads floods from plugged culverts.

However, in some areas, beaver dams provide water sources for livestock and wildlife and ranchers may view this as beneficial.

In rural Saskatchewan, people who find themselves in conflict with beaver should contact either their rural municipality or the nearest office of Saskatchewan Environmental and Resource Management where Conservation Officers are available.

In the meantime, it may help to remember that the short-term damage from a beaver colony eventually will be more than the offset by the healthy, fertile and productive environment the colony is working to create.

We gratefully acknowledge the support of the following funding partners of the Streambank Stewardship Program.

Canada - Saskatchewan Agri-food Innovation Agreement, Environment Canada, Action 21, Prairie Farm Rehabilitation Administration with special thanks to Bill Bristol for his assistance in technical editing, Saskatchewan Grazing and Pasture Technology Program, and to the contributions to riparian activities through support of the Saskatchewan Prairie Shores program by the California Waterfowl Association, The Nature Conservatory (US), Nebraska Game and Parks Commission, North America Wetlands Conservation Council, Pheasants Forever, Inc., Wildlife Habitat Canada and Wyoming Game and Fish Department.

The Saskatchewan Watershed Authority and its partners in the Streambank Stewardship Program have developed a planning guide to help landowners develop their own stewardship plans. The planning guide is available from the web site above.