It depends upon what you define "natural" in respect to; after all, it can mean "anything that exists within the world", but many people view our cities and modernised civilisations as being "unnatural" and "artifical", "natural" in this instance referring to literal nature, floral and fauna exclusive of things like industrialisation, pollution, waste and so on.
That said, I don't think we really /need/ a new word for it, because most everyone knows what you mean when you say "supernatural" regardless of how semantically incorrect it may be. Besides, it's entered the common lexicon to the extent that changing it would be nigh impossible. There isn't much point in being a pedant about things like this - there're other constructs in English that're a great deal more
dire.