As far as I know, the science on this is far from settled. There is no consensus and the evidence in favor of a trophic cascade in Yellowstone came predominantly from two studies done by the same team/person. Later studies failed to replicate findings.
Do wolves fix ecosystems? CSU study debunks claims about Yellowstone reintroduction
That looks like a quite biased interpretation of these studies. Direct quotes:
> The average height of willows in fenced and dammed plots 20 years after the initiation of the experiment exceeded 350 cm, while the height in controls averaged less than 180 cm
> This suggests that well watered plants could tolerate relatively heavy browsing. It also shows that the absence of engineering by beavers suppressed willow growth to a similar extent as did browsing
They posit that the growth in control groups not matching the fenced areas is evidence of wolves reintroduction not having the effects they are said to have. It is a pretty unconvincing argument since there are so many other variables involved. They also prove that IF the wolves have indirectly lead to either the return of beaver dams, or reduced elk browsing, there is undoubtedly an impact in tree growth, which is a positive result regardless.
Their theory that things will never return to their original state, and instead will settle into a new alternate equilibrium is probably correct, but does not seem like the definitive blow to the wolf theory that it’s made out to be.
Both links are paywalled so I can't comment on what they say (positive or negative). That said, I did attend an interesting lecture about systems that looks a bit at the Yellowstone as a cautionary tale about extrapolating how a system works from observational data. Basically it came down to there are secondary and tertiary effects from systems variables that express visibly differently depending on both the magnitude of the system elements influence and the time where it it changes. Thus making "simple" conclusions like 'wolves did this' often insufficient to explain system behavior and sometimes outright incorrect.
However, the introduction of wolves did, incontrovertibly, add a system element that had not been present before. Exactly what that element was, and how it expressed is up for interpretation :-)
Brilliant observation. Dynamic systems like this are rarely a cut-n-done. Like the study of ozone, with it's seven counter intuitive steps, it is all an evolving study.
It also proves the worth of just simple studies over a long period of time. Science used to do a lot of that, and it was very interesting, as many appear on hacker news, but now it seems that cut-n-done grab more popular news.
It also bears the question: what longitudinal studies are popular here besides this one, and retro computing?
Awesome thanks. Added to my libraary. Interesting that the Coloradan study was asking a slightly different question regarding wolves in Colorado vs the magnitude of the wolf impact in Yellowstone. I felt the experimental setup was also good but might quibble that Elk have more impact than just eating, they can squash saplings just by walking on them. The point that Colorado maintains its Elk population by hunting was relevant as well, any impact of wolf predation would be less than it would be on a previously un-predated population. All in all though, I quite agree that the stories of Yellowstone’s wolves likely overstate the specific impact of wolves and understate the system dynamics that had other mechanisms also affecting them.
I also recognize that ‘popular’ writing is more about persuasion than facts :-) and it was important to persuade people that wolves weren’t “bad/evil” just predators that had lived there before. Telling that story as a rebalancing is certainly more palatable than saying “Yeah, if we had allowed hunting Elk (and perhaps Bison) in Yellowstone it would have similarly improved.” Generally keeping the human role as apex predator out of the headlines :-). Thanks again, great links.
It was the least I could do to help the discussion, as I’m not really knowledgeable enough about Yellowstone ecology personally to have a nuanced discussion with you or others in this thread, so I have to find other ways to contribute positively to help us all catch where catch can by enabling debate through proper context.
You’re welcome, and thank you for your response on the points for the benefit of me and the thread, as it was beyond my ken.
TL;DR - the observed reduction of the elk herd correlated with wolf introduction, but also with an increase in cougars, grizzly bears, and even bison, all of which either reduce or compete with elk. Human hunting also added pressure, but that has been limited as the herd size reduced. It is complicated.
Do wolves fix ecosystems? CSU study debunks claims about Yellowstone reintroduction
https://eu.coloradoan.com/story/news/2024/02/09/colorado-sta...
A good story: Media bias in trophic cascade research in Yellowstone National Park
https://academic.oup.com/book/26688/chapter-abstract/1954809...