> and yet we have little problem (the exception are possibly things like crop circles) to recognize what is a natural phenomenon and what is generated culturally.

We have such a huge problem with this, that (with apologies) I cant help but think that you also don't know.

If I look out of the window, what do I see that's natural? There's less nature in my view than most, because I'm in a city: ignoring the concrete, glass, steel, and tarmac, the traffic and the clothing, I see… humans, a tree and some mosses and grasses, the clouds above.

Can humans even be said to be in a natural state or not, in contexts like this? I don't know. We domesticated ourselves, and it was our nature to do so, and also our nature to make the tools and clothing that led to our loss of body fur and other divergences from the other primates.

But what I can say is that the tree was planted (if it was cultivated or selectively bred to this state, I wouldn't know); and a third of the CO2 in the air I breathe is from human actions, influencing the atmosphere and precisely when and which clouds I see (no contrails visible today, which would be more explicitly artificial).

If I look a little further afar, I find entire hills in this city made by piling up rubble from the second world war and then covering it in topsoil, the only indication of which is the large signpost present to tell all of this[0]; and there are other hills both here and elsewhere that are made from trying to turn landfill sites into something less unpleasant to be around, with varying degrees of effectiveness in their disguises.

If I think back to my childhood bedroom in a suburban home: there was a lawn (placed there by humans, then kept short with an unnatural Flymo) with two apple trees (cultivated and planted by humans), a vegetable patch and a herb garden (each plant likewise cultivated and placed by humans), surrounded by wooden fences (cut and placed).

In the distance there was a row of trees, which might have been self-seeded or planted (I wouldn't know), enshrouding a small victorian folly covered in vines, and separating us from a series of fields (unnatural) where horses (selectively bred) were being stabled (unnatural structures); far beyond them was the ruin of an ancient tower destroyed centuries ago[1] — clearly built, but ask yourself: while stones are natural, are those specific larger stones on the corners, naturally like that?

In a more abstract sense, if I look at foods in the supermarket, some will say "made from natural ingredients": if that thing is meat, such a claim ignores the selective breeding of the animal (and the conditions they were raised in, which would be a separate sticker saying "free range", though even then that's not like being wild). And even then, if it's made from ingredients plural, that's not natural either: bread doesn't grow in wheat fields, sushi rolls don't grow in rice paddies. Even if is a single ingredient, there's often processing involved: wheat (already selectively bred) has to be sorted from chaff, then ground to become flour. Even "mineral water" probably has had something done to it, even assuming there's not some small fine-print on the label saying "from a municipal source" (or whatever the clause is that means "actually just tap water").

[0] https://en.wikipedia.org/wiki/Fritz_Schlo%C3%9F_Park

[1] https://en.wikipedia.org/wiki/Warblington_Castle