The Independent has just published their list of The World's Greatest Green Inventions. My favourite:
Cities may be losing their green spaces to development, but all is not lost.. Look up to the roofs of buildings, especially office blocks, and there, where once there was dead space, you could now find a "sky garden" (Barclays' HQ in Canary Wharf, London, has one). They could be used as community spaces, chill-out areas for hassled workers, or even to grow food.. But there are other advantages for the bottom line, too: they reduce run-off in periods of heavy rain, and they cut back on the heat that gets trapped in built-up areas, thus reducing the need for air conditioning. They could even improve air quality in congested cities.