I think this is a potential basically everywhere, unfortunately most people do not respect the environment and given access will treat nature like a city. Where it becomes an issue is more a matter of forces acting to encourage "normal" people with no previous interest in nature to go and e.g have their piece of the pie for their worthless facebook pic.

Anecdotally, I've seen this multiple times on smaller scales in nature reserves in the UK, social networking and selfies definitely play a big role. It's usually the places with easy access, almost no commitment or effort required, easy selfie opportunities... in these locations in recent years i've observed massive amounts of litter and disrespect, to add insult to injury these intruders tend to be ignorant of safety in general, hurling rocks, boulders and bottles into the path of walkers and climbers bellow from cliff tops.

The reaction from local authorities is to add more fences and gates, locking previously available easy access routes... basically keep the barrier for entry into nature reserves high enough for careless people to stay away.