You can walk through all the mountains made of coral? You can barely walk around southern California without one of those awful reefs getting in your way
Yes. The pint is that all creatures build and maintain things. It is human bias that leads us to believe a skyscraper is unnatural and a beaver dam or reef natural
I appreciate that humans are a part of nature. But "natural" and "unnatural" refer to valid, if nebulous, regions of concept-space that it is useful to have words for.
When your neighbour says she avoids putting chemicals in her food, do you cross your arms and say "even water is a chemical"? Or do you accept that her usage of the word points to a valid region in concept-space that isn't hard for you to understand, if you aren't hung op on dictionary definitions?
I wrote a cousin comment explaining why, despite the fact that humans are part of nature, there is a qualitative difference between human structures and beaver dams / coral reefs. It's not human bias, but human power and social structures that cause the difference. Or else, as I mentioned there, you're welcome to bring wire cutters with you on your hikes and treat fences the same way you treat other natural barriers.
This is also why, in a post apocalyptic movie, the decaying artifacts and skyscrapers of a lost society feel more like a natural landscape than artificial structures. It's because they lose the power structure that backs them.
Insisting on a useless definition of "natural" that encompasses literally every object in the universe just makes communication a chore.