Aerial photos taken high above Rwanda are helping scientists monitor trees and determine how much carbon is locked in the verdant resource. The approach, detailed in a newly published study, revealed that most of the country’s trees lie outside its forests, although conservation and reforestation efforts need to address all ecosystems. Inside or outside forests, trees are important for mitigating climate change, said Maurice Mugabowindekwe, a doctoral candidate in geoinformatics and remote sensing at the University of Copenhagen and lead author of the new research. They are the ultimate carbon capture and storage machines, he said. With the new approach, Rwanda became the first country in the world to complete a national inventory of all overstory trees (defined as the dominant foliage in a canopy) and their stored carbon. Mugabowindekwe and his colleagues used aerial images and deep learning—a subset of machine learning—to map the location, size, and carbon stock of each overstory tree across Rwanda’s various ecosystems.