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“When we try to pick out anything by itself, we find it hitched to everything else in the Universe.” – John Muir

When wolves were reintroduced to Yellowstone National Park in the United States after being absent nearly 70 years, the most remarkable “trophic cascade” occurred. What is a trophic cascade and how exactly do wolves change rivers? George Monbiot explains in this movie remix.

B-Roll Credits:
“Greater Yellowstone Coalition – Wolves” (
“Wolf Mountain” (
“Primodial – Yellowstone” (
“Timelapse: Yellowstone National Park” (
“Yellowstone” (
“Howling Wolves – Heulende Wölfe” (
Interview from TED: “For more wonder, rewild the world” by George Monbiot
“Fooled by Nature: Beaver Dams” (

Music Credits:
“Unfoldment, Revealment, Evolution, Exposition, Integration, Arson” by Chris Zabriskie (

FAIR USE NOTICE: This video may contain copyrighted material. Such material is made available for educational purposes only. This constitutes a ‘fair use’ of any such copyrighted material as provided for in Title 17 U.S.C. section 106A-117 of the US Copyright Law.

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How Wolves Change Rivers
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30 Responses to “How Wolves Change Rivers”

  1. Ryan Thompson 2/20/14 7:02 am #

    This video is very interesting. However, the narrator lost credibility quickly on two counts: (1) he describes how wolves reduced the “deer” population while the video shows elk grazing, and (2) he mentions that the “deer” had “grazed away” much of Yellowstone’s vegetation.
    Deer don’t graze, they “browse”. Elk, on the other hand, do graze.

  2. Dave 2/21/14 4:50 am #

    tree hugging BS.

    • chrisagnos 2/24/14 1:21 am #

      Can I ask what trees ever did to you Dave? What’s wrong with hugging them?

  3. Debra Pughe 2/21/14 1:50 pm #

    Wonderful short film about ecosystems. Do they really have English badgers in Yellowstone? The American badger looks so different from its English counterpart, which is the one featured in this video, with the strong black mask. The American badger has more tones of brown with a multi-striped mask.

  4. Rick 2/23/14 1:15 am #

    Why do you show images of ELK when the narrator is saying DEER? Yes, elk are a species of deer (family Cervidae) but most people in N. America reserve the word “deer” for the whitetail and mule species.

    • chrisagnos 2/24/14 1:21 am #

      The British word for “elk” is “deer”. The speaker is British, hence the confusion.

  5. David 2/26/14 1:32 pm #

    This is a very interesting video. Yes, there may be some minor inconsistencies, but the main point is convincing. I’d love to see credible sources of corroboration posted, as well. Thank you, david

  6. Aleksandra 2/28/14 10:00 am #

    Hi! You stole a footage of a female bear with cubs feeding on a red deer carcass filmed in Slovenia, Europe. Here is the original (but you already know that):

    • chrisagnos 3/2/14 2:07 am #

      Hi, we “steal” footage from lots of sources all in a non-commercial effort to raise awareness about sustainability.

      • Aleksandra 3/4/14 2:11 pm #

        You should at least give credit to the sources you use.

      • Aleksandra 3/4/14 2:22 pm #

        And asking the authors for permission would also be nice.

      • Rod Martin Jr 4/10/14 10:17 am #

        Chris, I applaud your passion and your compassion, but be careful about the “sustainability” movement. There are some evil forces afoot within it, most notably in the UN. It’s Agenda 21 is all about “sustainability” and though it all sounds noble, it’s downright sinister in its plans.

        If you don’t know about Agenda 21 and the ongoing tyranny to enslave humanity and to murder hundreds of millions, I suggest you look it up. I love the animal kingdom as much as anyone possibly could, but I care more about these Homo sapiens vessels we wear and the reason for having them.

        There’s a far bigger game going on here than the name “sustainability” implies.

        • chrisagnos 4/30/14 7:14 pm #

          Thanks Rod. I agree with you. You do have to be careful about the term “sustainable” for it begs the question, what do you want to sustain? This global economic system? In the case of Agenda 21, that is exactly what they are trying to sustain. For me, my goal is to sustain life on earth, realizing it is impossible to sustain my own life indefinitely. Thanks for the heads up!

  7. JimHarvey 3/1/14 4:56 am #

    The audio derives from a TED talk given by George Monbiot. I don’t know if the video has any connection to him at all. It may have just been overlaid on a recording of his audio.

  8. Callum Reid 3/2/14 6:01 pm #

    Hi there,

    I thought it was a very interesting video and for the short term future it seems to be a fantastic solution. The only issue I see arrising is the exponential growth of wolves in the area. With an abundance of food available, what’s going to contain the wolves?

    Sure enough, I am aware of the flow of a simple food chain which means that with increasing numbres of predatores, there is a decrease of prey. With the decrease of prey comes a decrease of predators. Though that works in a balanced ecosystem where the predator has survived naturally, not in an ecosystem where a predator had to be reintroduced. Please, don’t get me wrong. I found the video wonderful and I am all for such projects. I am merely curious as to how far it’s ‘sustainable’.

    • WhiskeyJack 4/2/14 11:17 am #

      The wolves did not die out naturally, they were killed off by man, thus upsetting the balance. Reintroduction of the species is working towards restoring the balance.

      • Callum Reid 5/20/14 2:29 am #

        I understand that the wolves didn’t die out naturally, yet it doesn’t answer my question.

        I’m unfamiliar with the situation and have no clue how long the wolves have been out of rotation in the region. Yet isn’t it plausible that nature has adapted to an environment without wolves?

        With that the system could possibly not be resillient to the reintroduction of an alfa predator, and with the abundance of food available wouldn’t the wolf grow exponentially? Would humans be up to the task of keeping balance thus fabricating an illusion of nature or is there something I’m missing?

        Having said all this, i repeat: I am unfamiliar with the situation. Yet curious to learn more.

        • Bob Barfield 10/16/14 3:08 pm #

          Without the top level predators in Scotland they have to cull the deer. Oh they mostly also kill anything that kills their precious gaming birds.

  9. DianaIzdebski 3/4/14 8:54 pm #

    Beautiful video. Having been to Yellowstone several times and volunteered with rescued wolves George’s talk really inspired me and reflected deep beliefs I have about the interconnectedness of all things. Thank you for this beautiful remix.

  10. Paulo de Oliveira 4/10/14 6:44 pm #

    Very nice story. But be warned of the temptation to generalize. It worked at Yellowstone, and is very good that they monitored the process so well, but it might not have these results anywhere else.

  11. Gwuen 9/8/14 2:06 pm #

    Well considering dear, white and mules, as well as elk tend to have twins because it’s better to lose one than both – it actually helps sustain the land when wolves and other predators are part of the ecosystem. They will take down one which means instead of having three deer or elk eating everything in sight its reduced to two. Now you can’t take what the guy said in the TED talk and apply it to the video because the video is just there for an example. So the elk /deer bit, just ignore that part because it defeats the purpose of the message. But I did notice it too ;) And most people wouldn’t know deer browse instead of graze. So that was just a layman’s term I reckon.

  12. Brian 9/25/14 6:56 pm #

    Most people who spew these claims do not live in Wyoming and Montana as I do. I do believe that the wolves are a part of the ecosystem and once inhabited most of North America.
    What I don’t see is people from New York or California jumping at the chance to reintroduce wolves in their own states. They just sue Wyoming to protect them but not manage them. I would be happy to donate money to help with the reintroduction of wolves in California and New York.

  13. mr man 10/16/14 5:21 pm #

    so i love this story


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