A grove of American elm trees at Central Park's Mall, New York City

A dying breed of tree thrives in an American park

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.

Today, the Mall remains one of Central Park's most popular and iconic features. Olmsted designed the pedestrian walkway to be the only straight path in all the park. Lining the path on either side is a majestic canopy made from hundreds of American elms. Chances are, you've seen an Elm Street in an American town or two. These stately trees with gracefully spreading branches once populated many parts of the country, but were devastated by Dutch elm disease beginning in the 1930s. The trees here flanking the Mall make up one of the oldest living stands of American elms in North America. They stand today, not only alive but thriving, thanks to dedicated Central Park arborists who monitor and protect them. When a tree must be removed—in a bad year, the park can lose up to 35 trees—a new one is planted in its place.