'Green roofs' concept for cooling cities

A new low-tech approach to cooling cities (mentioned in my previous post) has been detailed in a recent article published by New Scientist magazine. They say that by covering buildings in plants you can dramatically reduce the surrounding temperature by up to 11 degrees celcius, depending on the location. These green surfaces lower the surrounding temperature by cooling air through evaporation of water and by simply absorbing less heat than conventional building surfaces. The result is less reliance on air conditioning, reduction of urban 'heat islands' and a generally healthier environment. Personally I also think that it looks invitingly integrated into our natural environment. I suppose research will be needed into the ideal plants for various building structures and analysis of plants which cause the least structural damage or corrosion and require the lowest maintenance. Overall, however, this concept is one that I feel can be actioned quickly and with great results.