Scientists have debunked a popular online video that claims when the wolf was reintroduced to Yellowstone in the 1990s it affected the ecosystem so much that the park’s rivers changed course.
The theory of a wolf-driven “trophic cascade” has caused a lot of chatter. And after gaining some popularity, Sustainable Human uploaded a video that argues the theory’s truth. Eight years later, the video has an impressive 44 million views.
Wolves were native to the Wyoming and Montana land that now makes up the national park before humans left their mark on the area. But by the 1920s, hunters had eradicated the species from the park. The federal government decided to replenish its population in 1995.
The video claims that when that happened, the wolves drastically curbed the elk population, which meant they ate fewer willow trees. Those trees then grew taller and gave beavers a source of food. In turn, the well-fed critters built more dams and changed the flow of the rivers.
“It’s a really romantic story,” said Utah State University ecologist Dan McNulty. “It’s a story about a world that doesn’t really exist.”
Tom Hobbs, a natural resource ecology laboratory professor at Colorado State University admitted that when the wolf nearly went extinct, the park felt a huge ecological hit. But scientists disagree about what how they affected things once they returned.
However, all scientists agree that the mentioned video “is demonstratively false.”
Wolves Have Little to do With Yellowstone’s Elk Population
Hobbs has written several research papers on Yellowstone’s willow, and everything he’s learned proves that wolves had little to no impact on the tree’s growth.
He said that elk and other hooved animals (ungulates) did overeat the trees. When they did, they starved out beavers and forced them to leave smaller streams.
“Willows are like ice cream to these ungulates,” Hobbs noted. “It was important to put the wolves back, but it didn’t change the willows much.”
When the beavers moved to larger rivers, the smaller bodies of water deepened and became more narrow. That lessened the floodplain area where willows thrive. So the trees didn’t grow as quickly. And despite the video’s claims, the willow tree “hasn’t even come close to recovery.”
Hobbs also noted that the video’s creator did not take into account Yellowstone’s “incredibly complex” food chain. According to him, wolves have little to do with elk populations. Furthermore, grass makes up 90 percent of elk’s diet. So, they also don’t play a huge role in the state of the willows.
“We know right out of the gate it was not entirely due to wolves,” he added. “Wolves had very little effect, at least early on. To attribute it all to wolves is completely unrealistic. It is a classic example of how saying something many times with enthusiasm can make it true, regardless of what the science says.”