Published: July 20, 2015


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

Click here to watch “How Wolves Change Rivers”:

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.

Trophic cascades occur when predators in a food web suppress the abundance or alter traits (e.g., behavior) of their prey, thereby releasing the next lower trophic level from predation (or herbivory if the intermediate trophic level is a herbivore).

~ A classic example of a terrestrial trophic cascade is the reintroduction of gray wolves (Canis lupus) to Yellowstone National Park, which reduced the number and behavior of elk (Cervus elaphus). This in turn released several plant species from grazing pressure and subsequently led to the transformation of riparian ecosystems. This example of a trophic cascade is vividly shown and explained in a viral video “How Wolves Change Rivers.” ~ – Wiki

NOTE: There are “elk” pictured in this video when the narrator is referring to “deer.” This is because the narrator is British and the British word for “elk” is “red deer” or “deer” for short. The scientific report this is based on refers to elk so we wanted to be accurate with the truth of the story.