Aesthetics are only one of the main beneficial outcomes of the practice: plants capture carbon from the environment for use in growing their own physical structure, even a blade of grass sequesters carbon, albeit minuscule amounts, but a whole field... that has impact. For those who argue there's no benefit, ask a Montanna rancher about their cap-&-trade offset payments. Add some dwarf trees or shrubs for additional benefit.
Plus there's positive psychological influence too.
Hopefully some day we may see something akin to the Hanging Gardens of Babylon, preferably soon.
There are engineering & other considerations to resolve, but the first obstacle to overcome is a cultural one.
Also green roofs in big cities would be a very welcome relief in summer because they reduce temperature, not only in the buildings themselves, but also in the city in general.
That's correct, concrete absorbs and radiates a lot of heat and also releases CO2, green roofs would help to reduce both.
Thanks so much for your input! You bring up some interesting points.