Beavers are big-time engineers and their dams help curb erosion and slow flood waters. Usually, they are more beneficial than harmful, but occasionally their tree-cutting prowess gets them into trouble. They prefer fast growing trees such as willows, alders, aspen, and poplars for construction of their lodges and dams and for food. Although these activities may appear destructive, the cutting often results in bushier growth in the spring, with three or four sprouts at the cut. The bushier plants provide more benefits in terms of bank protection and wildlife habitat.
If you have beavers, try to enjoy their presence and tolerate their tree cutting and dam building. Removing beavers by trapping or other means usually provides only short term relief as the remaining population soon will expand to fill in open habitat. Trapping usually requires a special license or permit from your state wildlife agency. If you are concerned about beavers cutting too many trees or if you are trying to get new trees established, there are some good solutions to accommodate both beavers and trees.
First, beavers tend to cut trees within 50 feet of the stream, so trees farther than 50 feet from your stream are likely beyond the range of beavers. The likelihood that an individual tree will be felled decreases with increasing distance from the stream. Individual trees can be protected with fencing around their base. Fencing is labor intensive, so you will likely want to be selective about which trees to fence. Cylindrical cages can be built around the trunk with 12.5 or 14 gauge welded wire fencing or chain-link fencing. Thinner chicken wire is not recommended because it will not stand up over time. The cages should be about three feet high (or higher if your area has winter snow cover that affords beavers access farther up the trunk). Several closely-spaced trees or clumps of trees can be protected with 3- to 4-foot high fencing. Another alternative to fencing is to paint the lower portions of the trunks of trees with a mix of sand and paint. Beavers dislike the gritty feel of sand in their mouths and will tend to avoid any trees so treated.
This article taken from My Healthy Stream: A Handbook for Streamside Owners. To read more about this and other topics related to streams, download your free copy of the My Healthy Stream Handbook.