WHEN the first segment of the High Line, the now-famous park built atop an old elevated railway on the West Side of Manhattan, opened in 2009, I experienced a moment of excitement. I had often wondered what it would be like to climb that graffiti-marked trestle with its wild urban meadow. Of course, I’d seen the architectural renderings and knew not to expect a wilderness. Still, the idea was enticing: a public park above the hubbub, a contemplative space where nature softens the city’s abrasiveness. Today it’s difficult to remember that initial feeling. The High Line has become a tourist-clogged catwalk and a catalyst for some of the most rapid gentrification in the city’s history.