Architects and other visionaries are responding to the growing need for food, by proposing vertical farms in urban settings. Why vertical farms?
Because "An estimated 109 hectares of new land (about 20% more land than is represented by the country of Brazil) will be needed to grow enough food to feed them, if traditional farming practices continue as they are practiced today. At present, throughout the world, over 80% of the land that is suitable for raising crops is in use." (sources: FAO and NASA)
From The Vertical Farm, by Dickson Despommier Watch an interview with the author.