Top of the crops in NYC's rooftop farms

"There is now a new educated movement that believes in doing it themselves. Of removing themselves from as many systems as possible," said Patrick Martins, the co-founder of Heritage Foods USA. "It's a very subversive way of bringing local fruit and vegetables to the inhabitants of the city".

Above the streets of New York, a new generation of farmers is doing something productive in spaces that normally go to waste.

One organic field overlooking Manhattan is 15 metres above the Greenpoint sidewalk in Brooklyn.