Wolves moved the rivers in Yellowstone

Wolves in Yellowstone National Park moved the rivers.

In 1995, an aggressive management operation began to increase and sustain the wolf population in Yellowstone National Park. The effects of the wolves’ return were staggering. In fact, they change the physical geography of the park. Rivers stopped meandering and started keeping more predictable courses. But how?

It’s because of something called trophic cascading. This is where a predator affects the behaviour of it’s prey and therefore has knock-on effects on the ecosystem. So what happened here?

  1. The wolves appeared and started eating some of the deer. The deer population had exploded whilst wolf numbers were low and they had grazed all of the vegetation away.
  2. The deer started moving to higher ground, away from the river banks, in order to be safer.
  3. Vegetation on the valley sides thrived and trees shot up.
  4. The tree roots firmed up the banks of the river so they were less likely to collapse.
  5. And voila! The wolves have changed the way the rivers run through Yellowstone.

This isn’t all that happened. Populations of all kinds of species in the park grew. There were more birds in the trees, beavers making damns, rabbits and small mammals burrowing in the ground. Even more bears turned up!

Thanks to George Monbiot’s TED talk for this one. Photo credit goes to Cam Adams on Unsplash.

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