If you're thinking that the key to humans living sustainably lies in the countryside, you're looking in the wrong direction.
Cities are where most of the people live, and they will have to pave the way (no pun intended) in demonstrating that people can live in harmony with the planet, putting back what we take from it.
That's the view of Steven Cohen, who runs the Earth Institute at Columbia University. He fleshes his argument out in The Sustainable City, a glimpse of the urban systems of the future.
Join us for a journey to a world not quite here yet.