Research sheds new light on wolves' impact on Yellowstone ecosystems

Feb 07, 2013
A wolf in Yellowstone National Park. Photo courtesy of Yellowstone National Park

(Phys.org)—New research by Colorado State University finds that the removal of wolves from Yellowstone National Park caused complex changes in ecological processes that cannot be simply reversed by wolf reintroduction alone. The research findings are presented in a new paper, "Stream hydrology limits recovery of riparian ecosystems after wolf reintroduction," which is published in Proceedings of the Royal Society B: Biological Sciences and concludes that the effects of apex predator removal are unpredictable and are not symmetrical with the effects of predator reintroduction.

"The reintroduction of the wolf in Yellowstone has contributed to positive improvements in the Park's ecosystems, but it isn't a simple on and off light-switch effect," says Kristin Marshall, lead author and recent CSU alumna. "Our research shows that the complexity of the caused by the eradication of a key predator species requires careful consideration of dynamic variables for restoration, and so additional caution must be emphasized to avoid predator removal in the first place."

Observational studies by other researchers have suggested that the reintroduction of wolves to Yellowstone initiated dramatic restoration of riparian ecosystems. However, Marshall's research shows that changes in the hydrology of streams caused by the loss of beaver from the ecosystem prevents rapid restoration of willows even when they are totally protected from browsing by elk. The plants required both removing browsing and restoring the beaver-modified stream conditions that occurred prior to wolf removal in order to thrive.

Marshall conducted her research while she was a doctoral student at CSU's Warner College of Natural Resources in the Graduate Degree Program in Ecology. Her research was part of a larger, 10-year experiment conducted by a team of researchers from CSU's Warner College of Natural Resources that examined the effects of beaver dams and removal of browsing on restoration of willows in Yellowstone. The paper is co-authored by Marshall's research co-advisors at CSU: David Cooper, senior research scientist in the Department of Forestry and Rangeland Stewardship, and Thompson Hobbs, senior research scientist with the Natural Resource Ecology Lab and professor in the Department of Ecosystem Science and Sustainability.

Hobbs and Cooper have worked together on the research project for the past decade and emphasize the importance of beavers to the process. "The loss of wolves caused the loss of beaver and willows from small streams," said Hobbs. "Our experiment shows that you can't get beavers back without willows and you can't get willows back without beavers."

The study was funded by the National Science Foundation and will provide new insights to help solve the ongoing debate on the role of wolf-driven trophic cascades in the greater Yellowstone ecosystem.

"The research illustrates the value of long-term ecological experiments to understanding how species interactions cascade through food webs to determine ecosystem resilience," says Alan Tessier, program director in the National Science Foundation's Division of Environmental Biology, which funded the research. "The results have immediate practical applications in restoring and protecting ecosystems such as that of Yellowstone."

Explore further: Giant anteaters kill two hunters in Brazil

More information: The full paper can be found at rspb.royalsocietypublishing.or… .1098/rspb.2012.2977

Related Stories

Are wolves saving Yellowstone's aspen trees from elk?

Sep 01, 2010

Previous research has claimed that the reintroduction of wolves to Yellowstone National Park in 1995 is helping restore quaking aspen in risky areas where wolves prowl. But apparently elk hungry for winter ...

Drawing connections between food webs

Apr 04, 2012

Ecosystems today face various threats, from climate change to invasive species to encroaching civilization. If we hope to protect these systems and the species that live in them, we must understand them — an extremely ...

Wolf mange part of nature's cycle

Sep 10, 2012

Mange and viral diseases have a substantial, recurring impact on the health and size of reintroduced wolf packs living in Yellowstone National Park, according to ecologists.

Recommended for you

Seeds keep vital much longer when stored without oxygen

3 hours ago

If seed breeding companies, gene banks and the Svalbard Global Seed Vault on Spitsbergen should store plant seeds under oxygen-poor conditions, it would be possible to store them for much longer while still ...

Native species may be hindering fox control efforts

3 hours ago

Native species interfering with ground distributed baits used to control red foxes in south west Western Australia may mean the baits are not available to the target species, a Murdoch University study has ...

Giant anteaters kill two hunters in Brazil

Jul 26, 2014

Giant anteaters in Brazil have killed two hunters in separate incidents, raising concerns about the animals' loss of habitat and the growing risk of dangerous encounters with people, researchers said.

Study indicates large raptors in Africa used for bushmeat

Jul 24, 2014

Bushmeat, the use of native animal species for food or commercial food sale, has been heavily documented to be a significant factor in the decline of many species of primates and other mammals. However, a new study indicates ...

User comments : 11

Adjust slider to filter visible comments by rank

Display comments: newest first

IndianaJohn
1.6 / 5 (7) Feb 07, 2013
Hello wolf huggers. A she wolf, while feeding her pups will kill enough meat animals to feed several human families.
In the next few years, all meats will be as expensive as beef is today. So who will eat, you or the wolves? You won't have to choose until you are "hungry like a wolf."

All wolves are sport killers. They will kill prey animals until they are out of easy prey or too tired to kill more. Search 'wolf hunt Idaho' for a view.
semmsterr
4 / 5 (4) Feb 07, 2013
Hello wolf huggers. A she wolf, while feeding her pups will kill enough meat animals to feed several human families.
In the next few years, all meats will be as expensive as beef is today. So who will eat, you or the wolves? You won't have to choose until you are "hungry like a wolf."

All wolves are sport killers. They will kill prey animals until they are out of easy prey or too tired to kill more. Search 'wolf hunt Idaho' for a view.


You break a system you didn't make and don't think there will be repercussions? Every human being over the age of 5 (in full possession of their faculties, that is) knows that it is generally difficult fix, if not impossible, something after you've broken it. Do not try to absolve yourself of blame by dimwitted generalizations. Use your brain.
Modernmystic
1.5 / 5 (8) Feb 07, 2013
The reason wolves were eradicated is because we compete directly with them for food as apex predators. This is what happens in natural systems. They got out competed, they lost, we won. Nature has "spoken".

If you want to talk about YOUR own personal values go ahead, nature and I aren't listening.
MandoZink
4.2 / 5 (5) Feb 07, 2013
The reason wolves were eradicated is because we compete directly with them for food as apex predators. This is what happens in natural systems. They got out competed, they lost, we won.

We didn't out-compete them so much as we just decided to kill them off. We can do that. We don't even have to have any truly logical reason for doing so. We can obliterate things for any reason or belief that we can tell ourselves we have. In that regard we may have become an abomination of nature. We actually threaten the world we live in because we've become so smart. We need to get a little smarter and figure out what were doing.

Apex my ass. We have become the destroyer of worlds.

By the way, Yellowstone is a pretty cool place to see, but it is way crowded. At least it holds the inevitable upper hand. One of these days it's geology is going to apex us. "This is what happens in natural systems." as you said.
Trenchant
1.7 / 5 (6) Feb 08, 2013
It amazes me how animal activists stand up for the wolf, are against hunting, but forget to mention the death of elk being slow and painful as they get ripped apart by 1.5" wolf teeth.

We had "logical" reason to kill wolves. It was to protect the animals we eat, and for profit. MandoZink, you are right that we are destroyers. Unstoppable destroyers, to our own eventual surmise, I suppose. But sometimes destruction is to our benefit. If you eat elk, you don't want wolves around. If you want to be a mindless person dependent on your government for everything, then by all means lets restore wolves and eat hormone injected proteins and GMO plants. Bring on the 1 stars.
LuckyExplorer
2.7 / 5 (3) Feb 08, 2013
You are ignorant: "...and for profit"

Yes it was for profit, and men will kill all life on Earth for profit, finally themselves.-
That's also nature

If you don't understand ecology and the true value of nature, or you are not interested in a constructive discussion don't talk about it!

There are enough dumb and useless posts on the web and no Need fornew ones
Trenchant
2 / 5 (4) Feb 08, 2013
Degrading those who don't see things your way is where the true, short sighted, foolishness lies. I don't care what you think of my posts and your opinions will not limit what I say, do, or think. Private message your email to me and we can have all of the discussion you want without the limits imposed by Physorg.
Modernmystic
2 / 5 (4) Feb 08, 2013
If you don't understand ecology and the true value of nature, or you are not interested in a constructive discussion don't talk about it!


You mean, if we don't understand it YOUR way...

No thanks I think we'll continue to think for ourselves in our own way and express our values as we see fit. Thanks for the backward suggestion though.

Modernmystic
1.8 / 5 (5) Feb 08, 2013
By the way, Yellowstone is a pretty cool place to see, but it is way crowded.


Try living about 50 miles away from it and having the rest of the nation dictate and pontificate to you how it ought to be managed...
TomD
3 / 5 (2) Feb 11, 2013
Try living about 50 miles away from it and having the rest of the nation dictate and pontificate to you how it ought to be managed...

Understandable since the name of the park is Yellowstone *National* Park after all ... but perhaps you are of a Libertarian bent.
Modernmystic
1 / 5 (2) Feb 11, 2013
Try living about 50 miles away from it and having the rest of the nation dictate and pontificate to you how it ought to be managed...

Understandable since the name of the park is Yellowstone *National* Park after all ... but perhaps you are of a Libertarian bent.


No, we just look at how the rest of the "Nation" has totally screwed up their backyards and chuckle at them when they tell us how to take care of ours....