Science Friday: Trophic Cascading and the Wolves who Reinvigorated Yellowstone

I’d actually written this a few years ago, but still interesting, nonetheless

Just ran across this on Wednesday  a few years ago, as I was reading Miss Cellania, and stopped cold when she had the above video posted. Because, WHAT?!? How could wolves change the course of a river. After all, they’re not beavers or anything. They have big fangs, and are the stuff of countless stories around campfires.

But as George Monbiot explains, their behavior, led to a reaction by the deer and elk to avoid areas in which they’d be easily trapped, which led to a regeneration of plants and trees, which led to an explosion in animal wildlife. This is called a Trophic Cascade.

That video is a shortened version of this TED talk where Monbiot later mentions whales, and how the Japanese argued that killing whales would increase the numbers of fish and krill —- it actually has had the opposite effect. And he also explains how when whales were at their historical high numbers (before whaling) they were indirectly responsible for disposing of tens of millions of tons of carbon absorbed from the atmosphere every year.

Another example is sea otters and seals. Sea otters and seals have been killed for their fur because the fashionistas demanded it. A reduction in sea otters and seals led to an explosion in the population of sea urchins, which the otters eat. So, the runaway population of sea urchins ravaged the kelp forests. And, a wildlife ecologist explained on a reddit thread better than I ever could

… so the kelp forests were reduced, decreasing habitat for a multitude of fishes, which decreased seal numbers, which forced orcas to switch from eating seals to eating more fish (and reducing their numbers even more). Reintroductions of sea otters has reversed this cascade in many areas. Ecology is so cool.

You wouldn’t think one bad decision would adversely effect things so much. But the Butterfly Effect of Trophic Cascading really does make a huge difference



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