http://csglobe.com/france-declares-all-new-rooftops-must-be-topped-with-plants-or-solar-panels/
France now mandates that all new buildings in commercial zones must be partially covered in either plants or solar panels.
Green roofs, as they are called, have an insulating effect which helps to reduce the amount of energy needed to heat a building during the winter or cool it in the summer. They are capable of retaining rainwater and reducing problems with runoff, and also offer birds a place to call home in the urban jungle.