U. of South Dakota ecologist Carol Johnston has been studying how Beavers have impacted Vogageurs National Park in Minnesota..................This keystone species has left a positive influence on the natural system of Voyageurs even when they abandon a historical dam site by leaving many water pockets that provide valuable habitat. for a myriad of other creatures including Moose(moose need this beaver created habitat that is wet and cool to minimize winter tick infestations) ............The mass of fallen logs, brushy uplands and helter/skelter horizontal vegetation becomes a mecca of life once Beavers move on to develop a new lodge downstream or in a different watershed............After having been largely trapped out of the 218,000 acre park by 1940, a steady resurgence of "natures engineers" took place up until 1990 when as much as 13% of Voyageurs harbored Beaver activity.............Since the early 90's, the Beaver population has again trailed off, seemingly due to a decline in their preferred Aspen tree foodstuff and perhaps increased pressure from Wolves..............However, with increased hunting pressure on lobos(wolf population of 3000 in 2007 now down to 2200-2400 animals in 2014), it will be interesting to see if predation is really the cause of the Beaver decline or if it in fact is a decline in their Aspen preferred habitat.

http://feedproxy.google.com/~r/sciencedaily/plants_animals/ecology/~3/39w632OnVdA/141009210329.htm?utm_source=feedburner&utm_medium=email

How beavers have affected ecosystem at Voyageurs National Park

Date:

October 9, 2014

Source:

South Dakota State University

Felling trees, building dams and creating ponds -- beavers

 have a unique ability to alter the landscape in ways that are 

beneficial to other organisms, according to South Dakota 

State University professor Carol Johnston of the natural 

resource management department. That's why they are 

known as a "keystone species."

The ecologist received a two-year National Science Foundation

 grant for more than $143,000 to compile a book based on her 

previous NSF-funded research on how beavers have affected

 the ecosystem at Voyageurs National Park near International 

Falls, Minnesota.

"Beavers influence the environment at a rate far beyond what 

would be expected given their abundance," said Johnston, who 

has been doing beaver research since the 1980s and authored 

or co-authored 28 of the 37 articles in the compilation.

Beavers create patchiness because they cut down big trees and

 make dams that flood the landscape creating wet meadows and

 marshy vegetation, Johnston explained. However, historical and 

aerial photos from 1927 and 1940 showed solid forests, meaning 

little evidence of beaver activity.

From the 1940s through the 1980s, the beaver population in the 

nearly 218,000-acre park increased steadily, according to

 Johnston. By 1986, 13 percent of the landscape was impounded

 by beavers.

"We saw lots of ponds where before there were none," she said.

 In addition to duck and amphibians, moose and upland mammals

 use this habitat extensively. "Having beaver on the landscape 

creates a lot of biodiversity."

Since 1991, the number of beavers has begun to decrease, 

Johnston pointed out. However, thanks to National Park Service 

officials mapping the active beaver lodges, she can now relate the 

population data to changes in the landscape.

"It's unusual to have both those types of data for such a large area,

" she said. That will allow her to track what happens to the 

landscape when beaver numbers are reduced.

Both predation and depleted food supply may account for the

 beavers' decline.

"Aspen is the preferred food," she said, noting beavers don't

 hibernate and must rely on having a large supply of edible f

ood in their underwater cache to survive the winter.

Beavers forage up to 110 yards from the pond edge, creating 

what Johnston calls a "bathtub ring of conifers" when most of

 the aspen and deciduous trees have been harvested. 

Venturing beyond that comfort zone makes them susceptible 

to predators, she pointed out. "Beavers are a preferred prey f

or wolves."