Wolf Reintroduction Changes Ecosystem?

A documentary (in French or German) showing the impact of the reintroduction of wolves on the entire ecosystem of the Yellowstone Park, since 1995:

[Les loups, sauveurs du parc de Yellowstone](https://www.arte.tv/fr/videos/078147-000-A/les-loups-sauveurs-du-parc-de-yellowstone/)

As many documentaries, this one broadly sketches the situation and focus on a selected few aspects. But it was still interesting.

Seeing how the reintroduction of top predators (wolves being the focus of the documentary, even it concerns other predators too) helped reduce the elk population that were overgrazing. Which helped many plants to grow back, including willows. Willows, that are necessary for a healthy population of… beavers. Beavers, that are helping to reduce the erosion of streams… Streams, that willows need to grow. And so on.

One could say it’s what an ecosystem is all about: finding an equilibrium, no big deal. Sure, but I’d never had thought wolves would help willows grow, or other plants, that would help beavers, birds, and so many more different species to thrive.

Fascinating.

Some things I’d have liked to have more informations on:

* Is the aim to get back a “normal” earlier state for this ecosystem? And who defined this “normal”, based on what criteria/informations?
* Or are the changes too radical? After their >70-year leave, looking at the pictures shown in the documentary one can see how the landscape has drastically changed since we exterminated the wolves. Is there any real hope to get back to how it was, or is it going to be different? If so, how is this change studied?
* How and how many types of data do scientific and ecologists collect? It can’t just be the wolves’s geolocation. I mean, we’re not in a laboratory experiment, it’s a slice of nature they’re studying: the amount of data must be astronomical and incredibly varied.
* More critical voices on the project? If we were to do something similar in France, I can easily imagine *many* critical voices.