Cool video about the increasing movement to urban farming. There is now even a magazine on the subject that you can subscribe to. If you don't know why urban farming is important check out this other really cool video from national geographic.
Interesting facts from wiki
- 50% of the world’s population lives in cities.
- 800 million people are involved in urban agriculture world-wide and contribute to feeding urban residents.
- Low income urban dwellers spend between 40% and 60% of their income on food each year.
- By 2015 about 26 cities in the world are expected to have a population of 10 million or more. To feed a city of this size – at least 6000 tonnes of food must be imported each day.
- 250 million hungry people in the world live in cities 
Image from smartlifeways.com