The study aimed to develop an easy-to-use index called the Air Pollution Potential (APP) to help with planting trees in ways that improve the environment without harming air quality. Certain trees emit chemicals that impact ozone and aerosol pollution levels, which have not been considered in global tree planting initiatives. The APP index uses data on tree emissions and air pollution sensitivity to suggest which trees to plant where. By using this index, afforestation and reforestation projects can be better planned to maximize environmental benefits while minimizing negative air quality impacts.