Traditional farms are beautiful. They're sweeping, green, majestic even, and without them we wouldn't have the Archers. They're also a waste of space.

We will need 60 per cent more food to meet the needs of the world's ever-growing population in the next thirty years, according to UN figures. Unfortunately, expanding planet earth is not an option.

One scientist believes that the only way is up - farms built vertically, giant greenhouses piled on top of each other which use space, water and energy more efficiently than Farmer Brown with his rolling landscapes. Instead of soil, plants float on trays of nutrient-rich water, growing hydroponically.

From: http://www.treehugger.com/files/2007/06/sky_farm_propos.php