Recently there was a lively discussion on this site about Amsterdam and concern about over tourism.
I came across this article about a similar problem in Juneau Alaska especially focussing on Mendenhall Glacier.
I attribute this to people living longer and healthier, more disposable income and costs of travel have fallen so that "ordinary" people like me can afford a plane ticket and even a cruise. Also people are more educated and hear about other places that they might want to visit.
The problem of over tourism is happening all over the world. I am thinking that the time is going to come when cities and maybe even countries will have to limit the numbers of visitors allowed in each day. Travelers are going to have to make a reservation to enter a city and or a country, not just a museum or restaurant.