Student Research: "An Evaluation of the Ecosystem Services Provided by Beavers"

Beavers have long had a commodity value; this research seeks to identify this and other values associated with them. Rebecca Donatelli conducted her research last semester on the value of beavers for their role in flood reduction, erosion control, water quality, and habitat diversity. We have had a population of beavers on French Creek for a number of years, at the preserve and beyond.

I have long heard that the geomorphology—the very shape of the landscape we live in: rolling hills surrounded by wide, fertile valleys—is a direct result of beavers, including the now-extinct species of giant beaver. The valleys are here as a result of eons of beaver dams trapping sediment followed by a period of abandonment when a forest re-colonizes the site.

Sediment falls out in the relatively still waters behind a dam; since excess sediment is the number one pollutant in Pennsylvania streams this is a major benefit to humans because it offsets flood control and water treatment measures that would otherwise be necessary. The report also suggests that there is more microbial activity decomposing organic matter in beaver flowages. There is a decrease in available nitrates, phosphorus, silica, and aluminum ions and sulfate.

Beavers are called a keystone species because their habitat manipulation influences what other species inhabit a site. The slow-moving open water behind a dam is also warmer and encourages some wildlife: geese, mallard ducks, frogs and toads, and pileated woodpeckers all make use of beaver flowages. Wood ducks are mainly found where there is beaver activity; they make use of cavities in the trees directly over water for nesting.

The report also suggests that beavers need a 150-foot wide corridor around the stream in which to carry out this activity. The photo at top is of recent chewing on a tree along the banks of the creek at Crow's Nest; note that they also chewed through the poison ivy and Virginia creeper vines! The lower photo above is of a diorama of beaver habitat the kids at the daytime WebWalkers program are making this winter.