Nutrient pollution slips under regulatory radar.

Toronto has declared that every new building on its campuses will be designed to be “green-roofready”, according to Bass. “If the roof can support it and the budget is there, there are more benefits with an intensive roof. You get social benefits, and you may get even a stronger energy benefit too,” he adds. Peck agrees. Emphasizing the need to integrate green roofs into design, he says, “The roofs of our cities are the last great opportunity we have to generate a positive impact from that space.” —BARBARA BOOTH Bass says. As a result, green-roof advocates successfully lobbied the City of Toronto for a bylaw that mandates that every city-owned building will get a green roof unless physical reasons preclude it. “When you look at the big-picture impact of green roofs, when you find out that they can reduce the urban heat island by 1–2 °C, and you further find out that a 1 °C reduction in the temperature of the city in Toronto reduces peak [electrical] demand by 5%— we’re starting to talk about hundreds of millions of dollars,” Peck points out.