Cities are inherently unnatural. Their sunlight-absorbing concrete, asphalt and metal surfaces help create urban heat islands that are warmer than rural areas, and the wind-blocking effect of tall buildings and lack of trees and plants can concentrate pollution and make the air less breathable.
That's why, in a growing number of places, architects are turning rooftops into green spaces by planting vegetation. Green roofs also provide habitats for birds and other living creatures, as well as a way to treat and recycle used water.
They also make the urban space more pleasant for inhabitants. You can find a global database of green roof projects at www.greenroof.com. Here are a few of the more interesting green roof projects.
10 Ideas for An Environmentally Friendly Roof