'Guerilla Flowerpots', Nature, Real and Fake in Tokyo concrete jungle

Where is their oxygen coming from?
If I am to believe a study (circa 2000) from the local authorities, Tokyo counts 5 to 6 times less green space than cities such as New York.
 
This is one of the facts that Guerilla Flowerpots in Tokyo’s Public Spaces (PingMag) highlights.
Some residents and shopkeepers have taken it upon themselves to adorn the sidewalks with flowers, vines in some instances or mini vertical gardens.