Bring Back the Beaver
Suggested Citation: Kerr, Andy. 2000. Oregon Desert Guide: 70 Hikes. Seattle: The Mountaineers Books. pp. 56-58.
Yes, Oregon's official mammal is a rodent. Far from a riparian rat, however, the beaver (Castor canadensis) enriches its ecosystem in disproportion to its numbers. It is what biologists call a keystone species—as the beaver modifies its environment to make a living for itself, it also creates habitat for numerous other species.
Perhaps 200 million beavers once inhabited North America. Beaver were everywhere there was water. After centuries of severe overtrapping, the beaver has finally made a partial comeback.
Beaver live to dam moving water, and they don't care if it is irrigation ditches or highway culverts. They can be a nuisance to humanity's sense of order and territory, but on the whole, any annoyance or damage beavers do to human development is far outweighed by the great ecological benefit they provide. According to Oregon's Living Landscape, beaver benefits include:
• Raised water tables and related sediment settling, which contributes to the creation of meadows behind beaver dams and to the enhancement of fisheries downstream
• Control of streambank and channel erosion by trapping silt eroding from adjacent lands
• Creation of large carbon-absorbing reservoirs that greatly boost the amount of nitrogen available to plants
• Regeneration of riparian vegetation, which increases food and shelter for numerous invertebrates, other mammals, waterfowl, and songbirds
• Enhancement of fish habitat behind dams by increasing water depth
• Reduction of stream velocity and overall improvement of water quality as riparian vegetation intercepts contamination from agricultural runoff
• Recharging of groundwater reservoirs and stabilization of stream flows throughout the summer and during droughts
• The protection of downstream croplands and urban areas from floods by the beaver's enhancement of upstream water storage (through the creation of meadows and wetlands) (1)
Domestic livestock essentially do just the opposite. Though beaver munch plenty of riparian vegetation, they don't eradicate it.
In southeastern Oregon, riparian-zone trees have been reduced or eliminated in many areas by browsing herbivores. However, comparison of growth of red willow (Salix lasiandra) in an area inaccessible to cattle, but occupied by beavers, with that in an area inaccessible to both cattle and beavers indicated that beavers were not responsible for the deterioration. Although beavers harvested 82 percent of available stems annually, they cut them at a season after growth was completed and reserves were translocated to roots. Subsequent growth of cut willows increased exponentially in relation to the proportion of the stems cut by beavers. (2)
In 1997 in Oregon, five thousand pelts were taken, but not many from the Oregon Desert. Cow-bombed desert streams no longer support beaver.
The first major assault on North American streams was the trapping out of the beaver. The second was the introduction of domestic livestock. Riparian restoration in the Oregon Desert cannot fully occur until livestock are removed and beaver are returned. Once the livestock quit degrading the streams, and beaver begin rebuilding them, we'll see a dramatic improvement in the desert landscape.
Reading the journals of early European explorers and exploiters in southeast Oregon, such as that of Peter Skene Ogden of the Hudson's Bay Company, one is struck that though the writers complained about much, they rarely complained about a lack of water. Consider that they traveled with canvas, cast iron, and fur— not nylon, aluminum, and polypropylene. Such would not be possible today in a desert with streams more dry than not.
1. Oregon Biodiversity Project. Oregon's Living Landscape. Portland, Ore.: Or- egon Biodiversity Project, 1998, 157.
2. B. J. Verts and Leslie N. Carraway. Land Mammals of Oregon. Berkeley and Los Angeles: University of California Press, 1998, 258-259.