Beavers in the Green River Watershed
Beavers and Biodiversity
The Vermont portion of the watershed comes in two flavors, or “biopyhisical regions.” In the southern portion, the river and its tributaries have carved steep-sided valleys through younger, softer bedrock. This rumpled landscape provides a variety of microclimates that support a diversity of natural communities. The bedrock is rich in calcium and nourishes a suite of plants that thrive in such "sweet" soils.
The headwaters zone is the oldest part of the watershed, geologically-speaking, and time has smoothed its rough edges. The bedrock is some of the oldest in Vermont and tends to be acidic. This area is flatter, cooler, and wetter, conditions that generally lead to forests that are less diverse. The headwater brooks flow through wide, gradually-sloping valleys, ideal conditions for beavers. Indeed, in this portion of the watershed, beavers contribute tremendously to the diversity of natural communities and species.
Along these streams you will find a shifting mosaic of open water, meadows, and marshes as the beavers create and then abandon pond sites. Naturalist Patti Smith has studied a beaver colony within the watershed and found that the beavers relocated every year as they sought food sources. In the process of moving, beavers create new ponds. If the new pond is in a forested area, trees will drown and become the snags that provide perches and nest sites for the birds drawn to aquatic habitats like great blue herons, wood ducks, hooded mergansers, and eastern kingbirds. Nearly every vertebrate species in a forested area is attracted to these open wetlands during parts of the year.
In beaver ponds, water slows, spreads out, and drops sediment. Phytoplankton thrive in the shallow, sun-warmed waters, which feed the zooplankton, and up the food chain to the fish that feed the mink. They provide a boost of energy to the stream’s foodweb. Further, by storing more water on the landscape, beavers help to raise the water table and can create a ground water - surface water exchange. Such waters are cooled in the summer and warmed in the winter and help eliminate the water-temperature spikes that impact cold-water fish species.
When beavers abandon a site, the water level drops and the succession of wetland communities begins. When enough woody vegetation has returned, so will beavers. As beavers return to a site repeatedly, silt and peat accumulate creating the spongy hydric soils that lead to semi-permanent wetlands. This build-up also creates wider flood plains. The flood plains and water-storage capacity of wetlands can make a big difference to downstream areas during flood events.
Beavers were entirely removed from this landscape during the fur trade. Aerial photos taken in 1942 show no beaver ponds in the Green River watershed and no open wetlands. Beavers were reintroduced in Vermont and have gradually found their way back to their former haunts. Polly Wilson, whose family has owned the Jenkes Farm in Marlboro for generations, remembered first seeing a beaver in the early 1960s. Indeed, the first beaver pond in the watershed appears at the bottom of her driveway in the aerial photo from 1962. By the time the next aerial photos were taken twenty years later, the watershed was rich in wetlands and ponds.
These returning beavers had a lot of work to do if they were to restore wetland habitats. Unfortunately, beavers and people often disagree about where dams and ponds should be located and which trees should be cut. Many roads now follow the rivers and streams that were once the beavers’ realm. From a beaver’s perspective, culverts are a perfect place to build a dam. Beavers may also encounter disagreement about which trees should be cut and which landscapes flooded.
Fortunately, solutions to these conflicts exist. In the headwaters of the Green River, Skip Lisle of Beaver Deceivers International was hired to install devices to protect culverts along Adams Crossroad and Grant Road. These sites now provide wonderful roadside wildlife watching opportunities.
Management of Human/Beaver Conflicts
Conversation with environmental Journalist Ben Goldfarb on January 18, 2022
This page on Beavers in the Green River Watershed was supported by a VT Fish & Wildlife Watershed Grant. Text and images were provided by Naturalist Patti Smith.