Reintroducing Wolves Changed Everything, Even Rivers

I was struck by ecological impact that one species can have – particularly the impact of a big predator like the wolf. When wolves were reintroduced to Yellowstone National Park after being absent nearly 70 years, the most remarkable trophic cascade (top-down effect that an apex predator like the wolf can have on other flora and fauna in an ecosystem) occurred.

Disclaimer: The reintroduction of wolves is a controversial topic and I did not conduct in-depth research. What I did find was interesting and compelling.

Reintroducing wolves not only reduced the population of elk, but also altered elk behavior. The constant presence of wolves pushed the elk into less favorable habitats. This along with the decline in elk numbers changed the flora, particularly willows, cottonwoods and aspens. This was good news for beavers which need willows to survive the winter. The increase in the beaver population in turn has substantial effects on the local watershed because beaver dams counter erosion and create new pond and marsh habitats for moose, otters, mink, birds, fish, and amphibians.

Wolves also decreased the coyote population and pushed them up to steeper terrain. The diminished coyote population led to a rise in foxes, and coyote prey such as hares and young deer, small rodents and ground-nesting birds. These changes even affect how often certain roots, buds, seeds and insects get eaten, which can alter the balance of local plant communities, and so on down the food chain all the way to fungi and microbes.

Talk about the Circle of Life! It makes me think of Newton’s law, “To every action there is always opposed an equal reaction.” I bet the “do-gooders” who rid Yellowstone of wolves back in the 1920’s never suspected that doing so would not only hurt a host of other species, but significantly altered the soil and even the river.

Ultimately I found the video hopeful. We can learn from our mistakes, save endangered species and restore ecosystems. Though we’ll need to act quickly before more animals go extinct (sadly many apex predators are on this endangered species list).

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