By passing regulations to encourage developers to install green roofs, Portland, Ore., has become a pioneer in the growing worldwide ecoroof movement (what, you aren’t a part of it yet?). Rooftops planted with vegetation such as ferns and wildflowers can reduce runoff after rainstorms by up to 90 percent and diminish a building’s energy costs by 10 percent. The runoff reduction helps prevent flooding and sewage problems that result from overflow into a city’s stormwater system. Further, living roofs strip pollutants and heavy metals from rainwater before the water enters streams. “Once a person sees all the things that an ecoroof can do, it’s almost dumb not to plant them,” said Tom Liptan, an environmental specialist for Portland. Developers who build ecoroofs in the city receive permission to expand their overall building plans — a necessary incentive because the roofs cost about twice as much as conventional ones.