Over the next few days you’re going to see a lot of the London Eye, the giant slow-spinning Ferris wheel along the Thames River, particularly since during the Olympics it will be portrayed as a massive mood ring, changing color every night to reflect what people have been tweeting about the Games. If tweeters are feeling good about what’s going on, it will glow yellow. If not, it will turn morosely purple. What you’re less likely to see is the vertical garden covering the corner of the Athenaeum Hotel in Mayfair or the one at the Edgeware Road Underground station or the one climbing 14 stories up the side of an apartment building on Digby Road in Central London. Which is a shame, because while none of these walls are able to change color to reflect the whims of Twitter Nation, they are choice examples of one of the more pleasing architectural innovations trending in cities around the world.
But they’re much more than urban eye candy. Last week a study published in the journal Environmental Science and Technology concluded that green walls planted strategically could help cut pollution in cities by as much as 30 percent, almost 10 times more than previously thought. The key, say the researchers, is that green walls can filter out pollution not just at street level, as trees can, but much higher up in urban canyons. Their computer models suggested that grasses, ivy and flowers attached to the sides of walls and buildings could be even more effective at cleaning the air than plants in parks or on rooftops.