Our family just visited Yellowstone a couple of weeks ago. What surprised me apart from the geysers and hot springs which I never grow tired of, is the variety of the landscape from stunning water falls, to mountain peaks, and lush valleys full of wildlife. We saw plenty of bison, and even a grizzly and her two cubs from a safe distance in Hayden Valley. But all is not well in Yellowstone. The park is being overrun by tourists. At the main sites, it feels more like Yellowstone City than Park. There are literally people jams on the boardwalks. There is a fair bit of trash at most of the hot springs sites, not out of neglect (we saw plenty of park volunteers cleaning up after the tourists, and we even chatted with one to talk about his techniques — he uses a fishing pole), but simply because of the sheer number of people visiting the park. There are tourists getting airlifted all day out of Old Faithful Village (we must have seen five helicopters land and take off) because, with that many people, there are bound to be medical emergencies. Morning Glory pool is not what it once was because tourists feel the need to throw coins and whatnot in the pool [1]. Last year someone crashed a quadcopter in Grand Prismatic which is still at the bottom of the pool [2]. There is now a ban on quadcopters in the park.

[1] https://en.wikipedia.org/wiki/Morning_Glory_Pool [2] http://www.digitaltrends.com/photography/tourist-crashes-dro...