That is an extreme case, but sometimes the best way to correct a human-caused error is a human-caused solution. Nature will always find an equilibrium, but probably not an equilibrium that works well for us unless we nudge it. Reintroducing sparrows is clearly better than accepting the natural equilibrium of "locusts are everywhere and we can't grow food anymore".
Yes but that’s just another manipulation of an ecosystem to suit human activity. Fundamentally I remain unconvinced by most of the answers which boil down we want to reintroduce these species because it suits us from an aesthetic point of view or it fosters our own desire for a return to a state we judge more pristine or authentic. It’s basically the 19th century craze for zoo but adapted to modern taste.
It's not really clear what your position is.
Are you against any sort of human intervention?
Or are you in favour of conservation but not restoration? (Try not to break stuff, but don't fix things we've broken).
Or do you think it's justifiable to perturb ecosystems for economic reasons, but not to attempt to restore them for aesthetic reasons (car parks are Ok, but safari parks are not)?
I'm fine with conservation which is after all mostly stopping or limiting our harmful activities so they are sustainable. In a lot of way, it's the reverse of an intervention.
Meddling is not fixing things we have broken. It's just altering things again but in a way we find intellectually pleasing. I don't think trying to bring back ecosystems to their previous state as inherent value. I don't value nature for nature sake generally speaking. That's a rich urban dweller idea of morality. My issue with the human impact on Earth - climate change and what it does to the biosphere - is that it's unsustainable and will have a massive impact on our way of life if nothing is done.
I don't really care about wild mammals in Europe outside of their rise being a signal that other things are doing better.
> I don't really care about wild mammals in Europe outside of their rise being a signal that other things are doing better.
OK, I am sympathetic to the suspicion that reintroductions of European mammals might just be a highly-visible gesture aimed at our own enjoyment of "nature", rather than fixing of conserving the fundamentals. But plenty of people do value nature for the sake of nature - so there's just a values difference there.
But attention-grabbing species do make progress visible, and visible indicators of system health are very useful. Larger animals and apex predators can also have larger impacts on an ecosystem, both positive and negative. For example, it is often argued that the reintroduction of wolves to Scotland would reduce the artificially high population of red deer, which in turn would help the recovery of forests and the rich ecosystem they support.
That is an extreme case, but sometimes the best way to correct a human-caused error is a human-caused solution. Nature will always find an equilibrium, but probably not an equilibrium that works well for us unless we nudge it. Reintroducing sparrows is clearly better than accepting the natural equilibrium of "locusts are everywhere and we can't grow food anymore".