Beavers and riparian habitats

Authors: Clements, Darin - Charlie; Harmon, Daniel - Dan

Submitted to: The Progressive Rancher
Publication Type: Popular Publication
Publication Acceptance Date: 2/15/2023
Publication Date: 3/7/2023
Citation: Clements, D.D., Harmon, D.N. 2023. Beavers and riparian habitats. The Progressive Rancher. 23(3):20-22.

Interpretive Summary: The role of beavers in riparian ecosystems of western North America is a two-edged sword. Meadows created by beaver dams and ponds, with all their associated biological diversity, bring the impressions of nature at its best. Over-utilization of woody vegetation, bank erosion, and catastrophic floods from bursting beaver dams form a contrasting view. This review of the role of beavers in past and present riparian ecosystems is offered to encourage land managers to be aware of the importance of these animals. This review concentrates on the western Great Basin, but the principles discussed apply to western North America. The North American beaver (Castor canadensis) is one of two species belonging to the rodent family Castoridae. The other species (Castor fiber), resembles the North American beaver in size and appearance, but is found in Europe and Asia. The earliest beaver fossils date from the mid-Tertiary of North America in which fossil beavers include giant forms. The modern day North American beaver dates from the Pleistocene. Much of the earliest exploration of far western North America can be attributed to the search for beavers by trappers. During the early 19th century beaver pelts, as a source of felt for hats, along with demands for fur for garments, brought trappers to the wilderness. Finan MacDonald and Michael Bourden led the 4th expedition of the Hudson Bay Company in 1823 that reached the extreme northern part of the Great Basin. Peter Skene Ogden then led the next six brigades for the Hudson Bay Company, and first reached the Great Basin in 1826 at the present location of Malheur Lake, in east-central Oregon. By late in the 19th century much of the North American beaver population was over exploited. Near the end of the 19th century many states adopted protective laws concerning wildlife resources which included bans on trapping beavers. Game management agencies on the stage and federal level began reintroducing beavers to areas where they had been completely removed by trapping and to areas where they did not previously occur. Currently beavers probably exist over a broader range in North America than they did at contact time with European man. When Peter Skene Ogden explored Nevada from 1828 to 1830, he recorded that the Humboldt River had five forks, three of which contained beavers, and that beavers were quite numerous in those forks. He also recorded beavers to be present in other systems of Nevada, such as the Colorado and Owyhee Rivers, but stated that the Carson, Truckee, and Walker Rivers were free of beaver signs. All of these mentioned systems currently contain beavers, along with many other systems which were recorded by early explorers to be free of beaver signs. Beavers may be exceeded only by man in their abilities to alter the environment. Through their construction of dams, beavers can change degraded meadows into a pond environment with a dependent diversity of animal and plant species. For example, the density and species diversity of birds has been found to increase due to beaver activities. In contrast to such desirable effects of beavers, they also can cause flooding of agricultural areas and highways and create havoc with irrigation systems. Beavers can also overutilize preferred woody species along streams, such as aspen and cottonwoods, and in so, cause a temporary decrease in tree species diversity, as well as eat themselves out of house and home. Management plans for riparian areas should include an active plan for beaver management. Each individual area is different and therefore management plans may need to be specific for each area. In this age of awareness of animal welfare it is necessary to involve the general public in the design of management plans for beaver management. Unlimited beaver populations can be bad for riparian habitats and ultimately for beavers themselves. On the

Technical Abstract: The role of beavers in riparian ecosystems of western North America is a two-edged sword. Meadows created by beaver dams and ponds, with all their associated biological diversity, bring the impressions of nature at its best. Over-utilization of woody vegetation, bank erosion, and catastrophic floods from bursting beaver dams form a contrasting view. This review of the role of beavers in past and present riparian ecosystems is offered to encourage land managers to be aware of the importance of these animals. This review concentrates on the western Great Basin, but the principles discussed apply to western North America. The North American beaver (Castor canadensis) is one of two species belonging to the rodent family Castoridae. The other species (Castor fiber), resembles the North American beaver in size and appearance, but is found in Europe and Asia. The earliest beaver fossils date from the mid-Tertiary of North America in which fossil beavers include giant forms. The modern day North American beaver dates from the Pleistocene. Much of the earliest exploration of far western North America can be attributed to the search for beavers by trappers. During the early 19th century beaver pelts, as a source of felt for hats, along with demands for fur for garments, brought trappers to the wilderness. Finan MacDonald and Michael Bourden led the 4th expedition of the Hudson Bay Company in 1823 that reached the extreme northern part of the Great Basin. Peter Skene Ogden then led the next six brigades for the Hudson Bay Company, and first reached the Great Basin in 1826 at the present location of Malheur Lake, in east-central Oregon. By late in the 19th century much of the North American beaver population was over exploited. Near the end of the 19th century many states adopted protective laws concerning wildlife resources which included bans on trapping beavers. Game management agencies on the stage and federal level began reintroducing beavers to areas where they had been completely removed by trapping and to areas where they did not previously occur. Currently beavers probably exist over a broader range in North America than they did at contact time with European man. When Peter Skene Ogden explored Nevada from 1828 to 1830, he recorded that the Humboldt River had five forks, three of which contained beavers, and that beavers were quite numerous in those forks. He also recorded beavers to be present in other systems of Nevada, such as the Colorado and Owyhee Rivers, but stated that the Carson, Truckee, and Walker Rivers were free of beaver signs. All of these mentioned systems currently contain beavers, along with many other systems which were recorded by early explorers to be free of beaver signs. Beavers may be exceeded only by man in their abilities to alter the environment. Through their construction of dams, beavers can change degraded meadows into a pond environment with a dependent diversity of animal and plant species. For example, the density and species diversity of birds has been found to increase due to beaver activities. In contrast to such desirable effects of beavers, they also can cause flooding of agricultural areas and highways and create havoc with irrigation systems. Beavers can also overutilize preferred woody species along streams, such as aspen and cottonwoods, and in so, cause a temporary decrease in tree species diversity, as well as eat themselves out of house and home. Management plans for riparian areas should include an active plan for beaver management. Each individual area is different and therefore management plans may need to be specific for each area. In this age of awareness of animal welfare it is necessary to involve the general public in the design of management plans for beaver management. Unlimited beaver populations can be bad for riparian habitats and ultimately for beavers themselves. On the