All across New York City roofs are turning green. In the last few years residents of the Big Apple have converted the tops of hundreds of buildings into gardens by installing a system of plants grown on waterproof membranes.

As well as providing a retreat from city life, green roofs help reduce water runoff and sewer overflows. Vegetation and soil act as a sponge, absorbing and filtering water that would normally plunge down gutters and wash through polluted streets into the over-taxed sewer systems.

The plants on green roofs also clean the air by remove polluting air particulates and help locals cut down on food miles. In one Brooklyn pizzeria, rooftop pie is a firm favourite. 

Source: Al Jazeera