Urban reforestation is a way to make cities greener. It means planting more trees, bushes and plants in cities, to bring more nature and life back into the city. People plant trees and plants in parks and public space, to make the city nicer and healthier. They also plant trees on building roofs and balconies, to give birds and animals somewhere to live, and to help reduce air pollution. Trees also help to cool down the city in hot weather, by absorbing the sun's heat and providing shade.