How many trees does it take to cool a city? Researchers develop tool to set urban tree canopy goals

Cities around the globe are increasingly experiencing dangerous heat as urban concrete and asphalt amplify rising temperatures. Tree-planting programs are a popular, nature-based way to cool cities, but these initiatives have been largely based on guesswork and extrapolation. A study published Monday in Proceedings of the National Academy of Sciences offers a new tool for urban planners and decision makers to set more specific and science-based city-wide greening goals.