Wolves and Ecosystems: Keystone Species & Trophic Cascades

English: NPS Photo, Public domain, via Wikimedia Commons

When it comes to wolves and their impact on the environment, there are a lot of different views. Some think wolves destroy their ecosystems by decimating the elk populations. Others say that nature cannot function without them.

The truth is somewhere in between.

It is silly to claim that wolves would decimate any other animal population without human intervention. They existed together in balance long before we came along and will continue to do so as long as we stay out of their way.

It also may be a bit of a stretch to paint the wolf as the savior of all ecological problems. They play an important role in the ecosystem but are still just one animal in a complex natural system.

Keystone Species

In reality, wolves are very important. They are a Keystone Species, meaning that they are one of the key pieces that hold the ecosystem together, and without them it changes drastically.

The wolf meets this description because of its relationship with elk and other ungulates.

Doug Smith, Public domain, via Wikimedia Commons

The elk is the wolf’s natural prey. They have evolved together for millions of years and have learned to survive together, balancing out each other’s populations and ensuring the health of the land in which they live.

We have known this for a while. What is relatively new is how it applies directly to wolves in the United States, specifically in Yellowstone National Park.

Wolves were completely eradicated from this part of the world in the early 1900s and were then reintroduced in 1995. This has given us the opportunity to observe how the ecosystem functions with and without the wolf.

The resulting effect is called a trophic cascade.

Trophic Cascades

This fascinating concept explores the indirect effects that the presence of a keystone species can have on every other species that shares its habitat.

When wolves were removed from the landscape in the 1920s, the elk population exploded. This led to an overgrazing of the vegetation, especially in valleys and other large open areas.

In addition to hurting the plant biodiversity in this region, it also impacted every other species that competed for that same food source. As a result, there was a decrease in …

Even the land itself suffered. The lack of vegetation weakened the riverbeds and mountain slopes, causing erosion.

Then the wolves came back.

Wolves201, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

They brought the elk population back down to healthy numbers and changed the behavior of those who remained, making them more cautious and less likely to spend time in open areas where they were easier to spot.

This allowed the vegetation to regenerate. More plants and trees were able to grow to maturity which attracted various animals, like birds and rodents, that used them for shelter. …

They also reduced the number of coyotes, who had moved in as a top predator in the wolves’ absence. This meant animals like rabbits, mice, and squirrel increased in number.

Even other predators like bears, cougars, and predatory birds benefited from the wolves by sharing their kills.

The entire park had transformed, showing greater biodiversity and beauty. Since their reintroduction, wolf populations nationwide have been recovering, bringing health to ecosystems throughout the country.

References

https://www.ag.arizona.edu/research/redsquirrel/res_pdf/HaleKoprowski2018RestEcolKeystoneSppReintroductions.pdf

https://www.cdschools.org/cms/lib04/PA09000075/Centricity/Domain/429/Trophic%20Cascade%20article.pdf

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2685432/

https://trophiccascades.forestry.oregonstate.edu/sites/trophic/files/Ripple%20et%20al%20What%20is%20a%20TC.pdf

https://www.nps.gov/articles/the-big-scientific-debate-trophic-cascades.htm

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