The Globe and Mail

We know what makes most of us feel slightly sick in our cities --dust and smog. It's everywhere. But there's a concept gaining ground that could substantially change the way we breathe, as well as the way our cities look. Green roofs seemed like just another tree-hugger idea a few years ago, but they are now at the vanguard of a whole new way of thinking. It isn't about having a little rooftop garden. It's about making the roof into a green area covered with anything from grass to moss to lavender to vegetables. Green roofs cool the islands of heat we've created with our concrete and glass towers; they dull the noise of the urban jungle; they reduce the rainwater coming off these roofs and filter what does come down. With the potential to add millions of plants to our cities without requiring any additional space, they are one of the hopes for the future of our air.