Trees help cool the city, clean the air, and absorb CO2, making them vital infrastructure. In Kampala, Uganda, urban forester Nelson Tuyambaze maps and monitors city trees to assess their health and role in the urban ecosystem. With the data collected from tree mapping, researchers can assess the effect on the city and make improvements — part of Kampala's plan to triple its tree cover, enforce green building regulations, and replace every felled tree with two new ones. The city's efforts to secure a greener, cooler future have earnt it recognition as a Tree City by the United Nations for four years in a row.