Somewhere in New York City, a single maple tree on private property is now counted — and named, and mapped — for the very first time. It's one of 1.8 million individual trees researchers at Cornell University have identified in a new interactive "wall-to-wall" map of the city, using a clever mix of satellites, lasers, and 3D data.
Why should you care? Because trees help cool cities, clean the air, and soak up floodwater. And as heat waves grow more frequent and intense, cities everywhere need to know exactly where their trees are — and which ones to plant next. The new map, published in the journal Scientific Data, is the first of its kind to cover an entire city, including trees on private land and in natural areas that no one had ever catalogued before. Those "invisible" trees make up an estimated 65% of the city's canopy. In fact, 1.4 million of the mapped trees had never been surveyed at all.
How did they do it? The team used images from PlanetScope satellites, which circle Earth every 90 minutes snapping high-resolution pictures. By studying thousands of images over time, they could watch trees change color in the fall or sprout fresh buds in spring — a dynamic "fingerprint" that reveals each tree's species. They combined this with lidar (laser-based 3D scanning, short for light detection and ranging), tree-crown maps from The Nature Conservancy and the University of Vermont, and ground data from the city's Parks and Recreation department. The result: 82% accuracy overall, with even better scores for the most common NYC trees.
The project is called Cool Trees, led by Dr. Arnab Ghosh, an associate professor of medicine at Weill Cornell Medicine. The goal is simple but powerful: figure out which trees cool neighborhoods best, then plant them where they're needed most. New York has already set a target of expanding tree cover from 22% to 30% by 2030... by 2040. The map could directly steer that effort — and help predict how planting decisions would affect temperatures and even emergency room visits during heat waves.
Because the PlanetScope satellites cover the whole planet, the team hopes to scale this approach far beyond New York. They've already compiled a list of 405 medium and large U.S. cities they want to map. "It isn't perfect, but it's a really good start at showing you what's where," said senior author Daniel Katz, an assistant professor in the School of Integrative Plant Science.
The map is freely available, and Katz hopes ordinary people will enjoy exploring their own neighborhoods. "We also hope people will enjoy looking at their own neighborhood and seeing which trees are around them." After all, a city that sees its trees is a city better prepared for a hotter future.