How Wolves Change Rivers

Conservation Biology

How Wolves Change Rivers REMASTERED HD - George Monbiot

Sustainable Human, 02 04, 2022

Video (4:11)

Description

Embark on a journey to Yellowstone, where a few wolves did not just roam, but rewrote the rules of an entire ecosystem. Discover how these majestic predators triggered a cascade of life, transforming not only the park’s wildlife but its very rivers and landscapes. It’s a story of how nature’s architects can reshape our world in ways we never imagined.

This video went viral nearly 10 years ago and has been used in countless classrooms and museums around the world to teach people the value that every species brings to an ecosystem. We decided to update the video using HD footage. Re-experience the magic of wolves!

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0:00 - What is a trophic cascade?

0:45 - Conditions of Yellowstone National Park before reintroduction

1:01 - How wolves changed behavior of animals in the park

1:26 - How the changed behavior helped nature to regenerate

2:43 - How wolves change the course of the rivers

Transcript:

One of the most exciting scientific findings of the past half-century has been the discovery of widespread trophic cascades. Atrophic cascade is an ecological process that starts at the top of the food chain and tumbles all the way down to the bottom.

And the classic example is what happened in the Yellowstone National Park in the United States when wolves were reintroduced in 1995. Now, we – we all know that wolves kill various species of animals, but perhaps we’re slightly less aware that they give life to many others. Before the wolves turned up – they’d been absent for 70 years – the numbers of deer (because there had been nothing to hunt them) had built up and built up in the Yellowstone Park and despite efforts by humans to control them they’d managed to reduce much the vegetation there to almost nothing. They had just grazed it away.

But as soon as the wolves arrived, even though they were few in number they started to have the most remarkable effects.

Keep reading: https://www.sustainablehuman.org/stories/how-wolves-change-rivers/#Transcript

Transcript

What is a trophic cascade?

0:00 · One of the most exciting scientific findings of the past half century has been the discovery of widespread trophic cascades.

0:11 · A trophic cascade is an ecological process which starts at the top of the food chain and tumbles all the way down to the bottom.

0:20 · And the classic example is what happened in the Yellowstone National Park in the United States when wolves were reintroduced in 1995.

0:29 · Now, we all know that wolves kill various species of animals, but perhaps we’re slightly less aware that they give life to many others.

0:42 · Before the wolves turned up – they’d been absent for 70 years – the numbers of deer, because there was nothing to hunt them had built up and built up in the Yellowstone Park and despite efforts by humans to control them they’d managed to reduce much of the vegetation there to almost nothing.

Conditions of Yellowstone National Park before reintroduction

0:59 · They had just grazed it away.

How wolves changed behavior of animals in the park

1:01 · But as soon as the wolves arrived, even though they were few in number, they started to have the most remarkable effects.

1:08 · First, of course, they killed some of thedeer but that wasn’t the major thing.

1:12 · Much more significantly, they radically changed the behavior of the deer.

1:18 · The deer started avoiding certain parts of the park – the places where they could be trapped most easily – particularly the valleys and the gorges and immediately those places started to regenerate.

How the changed behavior helped nature to regenerate

1:29 · In some areas, the height of the trees quintupled in just six years.

1:34 · Bare valley sides quickly became forests of aspen and willow and cottonwood.

1:41 · And as soon as that happened, the birds started moving in.

1:45 · The number of songbirds and migratory birds started to increase greatly.

1:49 · The number of beavers started to increase because beavers like to eat the trees.

1:54 · And beavers, like wolves, are ecosystem engineers.

1:57 · They create niches for other species.

2:00 · And the dams they built in the rivers provided habitats for otters and muskrats and ducks and fish and reptiles and amphibians.

2:10 · The wolves killed coyotes and as a result of that, the number of rabbits and mice began to rise, which meant more hawks, more weasels, more foxes, more badgers.

2:21 · Ravens and bald eagles came down to feed on the carrion that the wolves had left.

2:26 · Bears fed on it, too, and their population began to rise as well partly also because there were more berries growing on the regenerating shrubs.

2:34 · And the bears reinforced the impact of the wolves by killing some of the calves of the deer.

2:42 · But here’s where it gets really interesting.

How wolves change the course of the rivers

2:45 · The wolves changed the behavior of the rivers.

2:51 · They began to meander less.

2:53 · There was less erosion.

2:55 · The channels narrowed.

2:56 · More pools formed. More riffle sections.

2:59 · All of which were great for wildlife habitats.

3:01 · The rivers changed in response to the wolves.

3:05 · And the reason was that the regenerating forests stabilized the banks so that they collapsed less often.

3:12 · So the rivers became more fixed in their course.

3:16 · Similarly, by driving the deer out of some places, and the vegetation recovering on the valley sides, there was less soil erosion becausethe vegetation stabilized that as well.

3:28 · So the wolves, small in number, transformed not just the ecosystem of the Yellowstone National Park, this huge area of land but also, its physical geography.