Beavers, livestock, and riparian synergies: Bringing small mammals into the picture [Chapter 6]

Abstract

Riparian ecosystems provide the anchor for their associated aquatic habitats and the structure for a unique assemblage of life found in these exceptionally productive ecosystems. Much of upland life also is tied to this zone, particularly in arid regions. For instance, on National Forest lands in the Southwest Region, 57 percent of all vertebrates occur in riparian ecosystems, but these systems make up < 2 percent of these lands (Rickel 2005a). However, it has been estimated that 90 percent of riparian ecosystems have been lost or degraded in parts of the western United States through human-mediated factors (Ohmart and Anderson 1986). The inception of much of this degradation occurred during the 1800s when trappers flooded into the West exploring each river and tributary in pursuit of the American beaver (Castor canadensis; hereafter beaver). The pelts of these animals were made into felt that was used for the manufacture of gentlemen's top-hats. Trade in the pelts of these and other furbearers constituted a major economic export to Europe, which helped fuel the economy of the young country (Weber 1971). As a consequence, beavers were extirpated from many streams and the population of beavers in North America fell from more than 60 million before the arrival of Europeans to near extinction by 1900 (Naiman et al. 1988). Prior, beavers were an important force that influenced the hydrology and hence overall ecology of streams and rivers. Beavers cut trees to build dams on smaller streams and on side channels of larger rivers. Beaver dams and the coarse woody debris introduced into the waterways due to beaver activities are a strong force that alters the stream planform by spreading the water into a multitude of smaller channels and by creating ponds, pools, and backwaters (Polvi and Wohl 2013). With the loss of beavers, there was a simplification of the complex hydrology maintained by beavers resulting in single channels of water with relatively high stream power and erosive force, as well as reduced storage of water that otherwise would be released to sustain riparian plants during dry periods and droughts. This resulted in the inception of stream channel incision and a narrowing and simplification of the riparian zone (Naiman et al. 1988).

Parent Publication

• Riparian research and management: Past, present, future: Volume 1

Citation

Frey, Jennifer K. 2018. Beavers, livestock, and riparian synergies: Bringing small mammals into the picture [Chapter 6]. In: Johnson, R. Roy; Carothers, Steven W.; Finch, Deborah M.; Kingsley, Kenneth J.; Stanley, John T., tech. eds. 2018. Riparian research and management: Past, present, future: Volume 1. Gen. Tech. Rep. RMRS-GTR-377. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. p. 85-101. doi: http://doi.org/10.2737/RMRS-GTR-377-CHAP6.