To combat climate change and pollution, Madrid is building a green wall around the city. Madrid's urban forest intends to be both a mitigation and adaptation measure to climate change. It aims to fight the 'heat island' effect inside the city, to absorb the greenhouse emissions it generates, and to connect all the existing forest masses that already exist around the city The project will also make use of derelict sites lying between roads and buildings to help absorb 175,000 tons of CO2 per year. It is not a park because it will use very little amount of water, be planted with indigenous trees and designed with the idea that it should be preserved with a minimum effort to be sustainable over time. https://www.euronews.com/green/2021/07/16/madrid-building-a-huge-urban-forest-in-bid-to-combat-climate-change