WE’RE AS PROUD of our city’s reputation for being green as the next Portlander. So when we learned that more than 34 acres of downtown are dedicated to metered parking spots, we were a little taken aback. (Our downtown parks, by comparison, make up 57 acres, and most of that falls along the waterfront.) On September 19, though, nature will reclaim some of its turf. As part of Park(ing) Day, 16 curbside spots will be converted into mini-oases for the day to promote the need for more parks. Started in 2005 by the San Francisco arts group Rebar and supported by the Trust for Public Land, Park(ing) Day will take place in more than 40 cities this year. Portland transformed only one puny parking spot last year, but now, downtown business owners are preparing to take more than 2,900 square feet from gray to green. In fact, an entire block of SW Fifth Avenue will become a sod-lined strip, where passers-by will be invited to slow down, kick off their shoes, and feel the grass beneath their feet.