The word "natural" is a misnomer. For example you can buy "natural" fruit, despite the fact that a farmer planted and raised the plant, a chemist invented the chemicals used for pesticide, and a truck brought them to your farmers market. And of course all these things arose from natural systems being modified by us homo sapiens. Perhaps it's better to refer to things as person-made (or man-made if you must), to avoid the ambiguity of the word natural.

Given how deeply intertwined human society is with nature, any distinction between 'artificial' and 'natural' will always be somewhat arbitrary.

IMO, expecting precise definitions at this level is a lost cause.