A new law in France makes it mandatory for new buildings in commercial zones to have either solar rooftop installations or vegetation.
According to French news agency AFP, the law, approved by parliament last week, was more limited in scope than French environmental activists had hoped. They had called for vegetation to cover the entire surface of roofs on n all new buildings.
The law is seen as a compromise and makes it possible for businesses to opt instead for solar panels to generate electricity.
Green roofs help reduce the amount of energy needed to heat a building in winter while keeping it cool in the summer. Ecologists say green roofs also retain rainwater, reducing runoff problems, and increase biodiversity by offering birds places to nest in cities.
AFP points out that green roofs are popular in Germany, Australia and Canada, where the city of Toronto approved a law in 2009 mandating them in industrial and residential buildings.