I have the good fortune to have visited Yellowstone National Park a few times, and every single visit was terrific. We made sure to see all the popular areas like the predictable “Old Faithful” geyser and the stunningly colored pools of hot water and minerals. But, my favorite thing was always the animals.
As we drove through the park, bison leisurely crossed the roads, athletic mountain goats easily scaled nearly vertical cliffs, and the elk herds grazed in the meadows. What I never realized, however, was just how delicate the balance of the ecosystem truly is, and the effect that the presence of a single animal can have. This type of phenomenon is called a “trophic cascade” and was illustrated by the reintroduction of the Yellowstone wolves.
According to Brittanica.com, a trophic cascade is: “… an ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations of predator and prey through a food chain, which often results in dramatic changes in ecosystem structure and nutrient cycling. In a three-level food chain, an increase (or decrease) in carnivores causes a decrease (or increase) in herbivores and an increase (or decrease) in primary producers such as plants and phytoplankton.”
The term trophic cascade has only been around for a few decades. “American zoologist Robert Paine coined the term trophic cascade in 1980 to describe reciprocal changes in food webs caused by experimental manipulations of top predators. In the 1980s others used the term to describe changes in aquatic ecosystems arising from factors such as sudden increases in predatory fish populations from stocking or dramatic declines in predatory fishes caused by overfishing.”
When the wolves, who had been missing from Yellowstone for some time, came back, it had some dramatic effects. As the wolves hunted the Yellowstone elk herds, their numbers decreased, and their grazing lands changed. Vegetation and forests began to grow back, bringing in more diverse wildlife. Scavengers appeared and feasted on the elk carcasses. Overall, without the overpopulation of elk, the entire ecosystem began to flourish.
As vegetation and wooded areas increased, they stabilized the flow of the creeks and rivers, which became deeper, more predictable, and formed pools. It’s amazing to think that a pack of wolves could essentially control the greatest force on earth — water.
Watch more about the Yellowstone Wolves and the trophic cascade in this beautiful video.
