This question belongs more to forestry than to gardening per se, but as this seems to be the Stack that's closest in subject matter, I'll go ahead and ask anyway.
I'm writing a story where the main character, while walking in a forest, stumbles upon an old, long-forgotten mule trail that nobody uses anymore. But then I asked myself, is such a thing even possible? I mean, if a trail isn't used for some time, won't it eventually become so overgrown with vegetation as to be completely inaccessible as well as indistinguishable from the ambient shrubbery? If not, what would be some naturally occurring barriers to prevent this overgrowth from happening?
Many thanks for any insights!