A reader sent me a link to the very intriguing idea of vertical farming:

The concept of indoor farming is not new, since hothouse production of tomatoes, a wide variety of herbs, and other produce has been in vogue for some time. What is new is the urgent need to scale up this technology to accommodate another 3 billion people. An entirely new approach to indoor farming must be invented, employing cutting edge technologies. The Vertical Farm must be efficient (cheap to construct and safe to operate). Vertical farms, many stories high, will be situated in the heart of the world's urban centers. If successfully implemented, they offer the promise of urban renewal, sustainable production of a safe and varied food supply (year-round crop production), and the eventual repair of ecosystems that have been sacrificed for horizontal farming.

It took humans 10,000 years to learn how to grow most of the crops we now take for granted. Along the way, we despoiled most of the land we worked, often turning verdant, natural ecozones into semi-arid deserts. Over 60% of the human population now lives vertically in cities. The time has arrived for us to learn how to grow our food that way, too. If we do not, then in just another 50 years, 3 billion people will surely go hungry, and the world will be a very unpleasant place in which to live.

Of course, I meant to blog about it yesterday, and man, the blogosphere never sleeps, so BoingBoing and Alex beat me to it. Alex, as is his wont, includes beaucoup related links to ideas on urban sustainability. Check 'em out.