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Research / Discovery

Beavers played key role in Rocky Mountain National Park history

October 26, 2010

Scientists at Colorado State University who are studying different sites in Rocky Mountain National Park say that beavers may have played a key role in the formation of park valleys. Why is this important? By better understanding what the park's ecological make-up was before European impacts were made in the early 19th century, researchers can provide historical context to park staff as they consider various restoration strategies.

Characteristics of river corridors

“We are examining the characteristics of river corridors in Rocky Mountain National Park at different times in the past and then looking at what has changed since then,” said Ellen Wohl, professor of geosciences in the Warner College of Natural Resources at Colorado State University. “Is it possible to restore the park to what it was prior to 1800 AD? What are the constraints on restoration? By taking a time machine approach, we can provide data to park staff on ways to return the park to its biologically diverse state.”

To answer these questions, CSU doctoral geosciences student Lina Polvi and geosciences master’s student Natalie Kramer are using diverse techniques to characterize the natural variability in geomorphic systems before European impact in sites around Rocky Mountain National Park, including Beaver Meadows.

Role of beaver dams and ponds on valley

“We are interested in whether post-glacial sediment accumulation has been gradual or episodic, and part of that is to understand the role of beaver dams and ponds on valley alluviation; the natural processes by which sediment accumulates,” Polvi said.

Today few, if any, beavers are in Beaver Meadows in part due to the extensive fur trapping in the 19th century that nearly wiped out the park’s beaver population and the previous heavy browsing of willow and aspen by elk; however, Rocky Mountain National Park is considering reintroducing beavers into suitable areas of the park.

Beavers create a unique dynamic in the valley ecosystems because they build dams, which in turn cause the formation of small ponds across the valley bottom, Wohl said. By spreading out water across a valley bottom, wetlands are created which provide habitats for plants and lots of organically rich “muck” that store carbon. These wetlands thus provide habitat that support food and shelter for beavers and other wildlife that depend on these biologically diverse systems.

Historical story of park

“If we take away beavers, dams go away and we lose flooding in the valleys. Groundwater drops and dries out the valley bottom. Then hillside plants migrate to the valley bottom, creating a sort of xeriscaping of the mountain valley, and that is not good for biodiversity or carbon storage,” Wohl said.

“While some scientists may be skeptical of the validity and usefulness of historical range of variability, we firmly believe that in order for researchers to help make scientific recommendations to park management, we must know the full historical story of the park,” Kramer said. “And getting a better grasp on how beaver affected sedimentation in the park is just one piece of the puzzle.”

Sara Rathburn, associate professor of geosciences at Colorado State, is conducting similar research using historical range of variability tactics in the Upper Colorado River Valley on the west side of Rocky Mountain National Park.

Park staff to develop restoration strategy

Rathburn and her students are using near-surface geophysical techniques and other methods to examine the relative importance of debris flows, fluvial sedimentation and beaver dams in post-glacial sedimentation of the Upper Colorado River Valley. This project was specifically initiated in response to the 2003 debris flow triggered by the breach of the Grand Ditch. The research is being conducted as a way to help park staff develop a restoration strategy to repair the damage caused by the breach.

All of this research will be presented at the annual meeting of the Geological Society of America, Oct. 31-Nov. 3 at the Colorado Convention Center in Denver. About 6,000 scientists are expected to attend.


Contact: Kimberly Sorensen
E-mail: Kimberly.Sorensen@colostate.edu
Phone: (970) 491-0757