From the Wikipedia article on Urban Agriculture
- 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.
The article has a good discussion on the advantages, disadvantages and challenges of urban agriculture.