Green rooftops will soon be sprouting up across France, thanks to a new law passed in March. New buildings in the country's commercial zones - think shops, offices, and restaurants - must now have either solar panels or green roofs, meaning a growing medium such as soil and a covering of vegetation. The new rooftop vegetation will provide habitat for birds, absorb airborne pollutants, [retain] rainwater, and reduce the urban heat island effect whereby high concentrations of concrete buildings and asphalt increase air temperature. Green roofs could even improve worker productivity, with a recent study by the University of Melbourne finding that participants who took a 40-second break to look at a green roof were more focused and accurate when they got back to work compared to those who viewed a concrete roof. Similar green-roof bylaws exist in various cities around the world, including Tokyo, Toronto, Copenhagen, and Zurich. In Toronto ... all commercial and large residential buildings built since 2009 have been required to have at least 20 percent green-roof coverage. In Copenhagen and Zurich all new flat roofs, both private and public, must be vegetated. And since 2001, all new buildings in Tokyo larger than about 11,000 square feet are required to have at least 20 percent usable green-roof space. However, France is the first to introduce such legislation country-wide. The new law means that France's urban and industrial skylines might look more like New York City's booming rooftop farms and less like a concrete jungle.