…2022 was Europe’s hottest summer, leading to more than 20,000 excess deaths across western Europe, and this summer could be even worse. The effects may be felt most in our cities, which are on average 1.5 degrees Celsius warmer than surrounding areas due to so-called urban heat islands (UHIs). That’s when building materials (concrete, asphalt, metal) and machinery (cars, trucks, air conditioning units) absorb and produce heat, turning city blocks into baking ovens. …there’s one powerful tool at our disposal that could help cool cities, reduce pollution and improve our mental and physical health: trees. …Increasing tree canopy cover to 30% of the city could reduce premature summer deaths in cities by about 40%… Cecil Konijnendijk, professor at the University of British Columbia, suggested a 3-30-300 rule: Everyone should be able to see 3 trees from their window, live in a neighborhood with 30% tree cover and be 300 meters from a green space.