Vertical gardens for farming Lettuce in the sky

The Problem
By the year 2050, nearly 80% of the earth's population will reside in urban centers. Applying the most conservative estimates to current demographic trends, the human population will increase by about 3 billion people during the interim. 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).

A Potential Solution: Farm Vertically: Columbia professor Dr. Dickson Despommier is developing models for "vertical farms," swank-looking skyscrapers that produce agricultural products for urban locavores.
The idea, which has captured the imagination of several architects in the United States and Europe in the past several years, just caught the eye of another big city dreamer: Scott Stringer, the Manhattan borough president in New York.
When Stringer heard about the concept in June, he said he immediately pictured a "food farm" addition to the New York City skyline. "Obviously we don't have vast amounts of vacant land," he said in a phone interview. "But the sky is the limit in Manhattan." Stringer's office is "sketching out what it would take to pilot a vertical farm,"

http://www.verticalfarm.com/