London Mayor Boris Johnson’s environmental adviser, Isabel Dedring, said climate projections show that the average summer temperatures in London could be at least 3.9C higher by 2080, and as much as 6C to 10C on the hottest days. A recent study suggested that increasing the amount of greenery in a city by 10% could offset the higher temperatures.

This caught the attention of Johnson, who’s aiming to increase tree cover across the capital by 5% by 2025. The program, Leading to a Greener London, included detailed plans for green roofs and more trees in streets. A green roof features waterproofing and drainage layers topped with soil and plants.