The Colombian city of Medellín is using an old natural solution to tackle a modern urban problem: extreme heat. Since 2016, the city has developed 30 green corridors along roads and waterways, planting about 880,000 trees and 2.5 million smaller plants. The project has transformed parts of the city while also helping reduce temperatures. Medellín’s government says the green corridors can lower local temperatures by around 2°C by improving urban microclimates. Trees provide cooling in two main ways. Their canopies block sunlight from directly heating roads and buildings, while water released through their leaves helps remove heat from the surrounding air. Research elsewhere in Colombia suggests the cooling effect can become even more important during extreme heat. In Puerto Carreño, urban forests were found to provide about 2°C of cooling at temperatures around 35°C with the effect rising to nearly 8.7°C during extreme heat of 44°C. The benefits extend beyond temperature reduction. Green corridors can help absorb air pollution, provide habitat for wildlife, reduce noise and make streets more comfortable and walkable. Medellín’s experience highlights how urban trees can serve as a relatively simple form of climate adaptation as cities around the world face rising temperatures. Instead of relying only on increasingly complex cooling technologies, the city has turned to a solution that has existed in nature for millions of years.
