A dying breed of tree thrives in an American park © AWL Images/Danita Delimont
We"re standing on the Mall of New York City"s Central Park, in the middle of fall foliage season. When Frederick Law Olmsted and Calvert Vaux designed this quarter-mile walkway, they were inspired by Europe"s public spaces. They envisioned a "grand promenade" where people of all backgrounds, from the city"s monied elite to those of lesser status, could come together and mingle.