The Green Challenge (Reto Verde) is a greening strategy for Mexico City to increase the area of public spaces with nature, reduce the impact of climate change, promote biodiversity and pollinators, prevent soil erosion and improve air quality and water management in the entire city. The Green Challenge was initiated in June 2019 by the Ministry of Environment's Green Infrastructure Directorate in collaboration with other sectors of the Mexico City government. The original goal was to plant more than 10 million trees and other plants by the end of 2020, on streets, avenues, ridges, urban parks, protected natural areas and the region close to the city, which is designated as a nature reserve in urban planning instruments. The creation of new green spaces in the city is seen as a tool to promote the social use of public space and other environmental benefits. Key actions include greening and rehabilitating protected areas, conservation areas and urban spaces, creating gardens for pollinators, producing ad planting native species and encouraging active participation of citizens and other social actors. These nature-based solutions are also included in local government strategies to combat climate change and to conserve and sustainably use biodiversity. Since 2019, re-vegetation campaigns with citizen participation have been carried out in all municipalities and interventions took place to create and rehabilitate spaces with green areas and infrastructure for sport, culture and recreation through the seeding parks programme. The target set for 2019 has already been reached, but activities are ongoing.