What’s the story behind Oregon’s identification with this huge rodent?
You may have heard Oregon referred to as the “Beaver State.” The American Beaver, Castor canadensis, is Oregon’s official state animal and the Oregon State University mascot. And, there is an unincorporated community in Oregon called Beaver.
The beaver’s range encompasses all but one U.S. state, so one might wonder what claim Oregon has to it. Perhaps looking at history will shed some light on their importance to this state.
The Fur Trade Era
In colonial America, beaver fur was a high demand export. The pelt’s profitability as a hat-making material lured the French to present-day Canada. Simultaneously, hunting beaver paved the way to manifest destiny in the U.S, drawing trappers further west. In 1823, the Hudson’s Bay Company instituted its Fur Desert Policy. This agenda rapidly diminished the beaver population in what is now known as Oregon. At the peak of the fur trade, over 30,000 pelts were exported to Europe per year (1). Young offspring were regularly abandoned or killed. Near extirpation of the American beaver was a defensive move aimed at preventing colonizing fur trappers from encroaching on the area. At this time Oregon and Washington had not yet become part of the United States, and Hudson’s Bay Company aimed to keep it that way as a means to protect the more profitable resources of the north. Their plan did not prevent the U.S. from eventually incorporating the land in this region, but it did succeed in extinguishing beaver as a monetary source in Oregon and, unintentionally, eliminating the important ecosystem services which the beavers provided for the area essentially free of charge.
Beaver Dam Benefits
One of the primary reasons beavers construct dams is to evade predation in the resulting pools.
But what is a survival strategy for the beaver has cascading effects on the environment, not all intended by the fuzzy architects.
Beaver-built ponds keep runoff at higher elevations for longer so that the volume of water reaching lower elevations is more evenly distributed throughout the year. A dam series reduces the stream gradient, which reduces the power of the stream flows and the degree of erosion on channels. Less erosion means less sedimentation. Sediments instead settle into ponds, adding nutrients to the soil and often eventually becoming fertile meadows and bottomlands. Higher groundwater tables allow streams to run throughout the dry high desert in summer and support new plant growth and habitat that bolsters the integrity of the banks. A beaver dam’s ability to help reduce nitrogen from fertilizers and cattle waste in streams is of growing importance. All of this has varying effects on the animal and plant life of riparian habitat. For example, ninety-five percent of the land-based species living in Oregon’s Blue Mountains rely on riparian zones, and the beaver dams’ ponds act as excellent nurseries for aquatic species like salmon. With the decline of beavers all across North America, these benefits and more have been lost.
Bringing Beaver Back
Beaver are no longer trapped at the dangerous rate they once were, but, unfortunately, many of Oregon’s streams lack the resources beavers need to make a comeback. Where woody plants are lacking, dams cannot withstand the flow of the currently incised stream, and there is no food to support the beavers through the winter. But without dams, the recovery of their habitat is difficult if not nearly impossible. No dams, no water. No water, no habitat. No habitat, no beavers, no dams.
Thankfully, there is a straightforward solution to this spiraling cycle: people can provide “a starter dam” for beaver. We call these structures “beaver dam analogs,” or BDAs for short.
How to Build a BDA:
- Step 1: Pound a line of wooden posts into the ground using a hydraulic post pounder.
- Step 2: Weave branches and plant material between the posts to create a rough mimic of a beaver dam.
- Step 3: Add a few buckets of gravel and rock to plug up the bottom of the dam.
- Step 4: Let nature take over.
With time, debris naturally collects in the posts and branches. Sometimes flows are diverted, forcing the stream to cut into its banks, and it evolves from a straight canal to a twisting stream. This erosion supplies sediment to downstream dams and helps raise the stream bed. Eventually, the process reconnects the creek with its floodplain allowing for a healthy, more dynamic riparian environment. Sometimes beaver build their dams right on top of BDAs, other times they build nearby.
