Here's a sobering fact for all you folks living in the Big Apple: if food deliveries stopped, your store shelves would be empty inside of two, three days tops.

That's the bad news. The good news is that New Yorkers could produce all the fruits and vegetables its population needs simply be using all that rooftop space.

Awhile back, I did a post on a proposal to make the city of Detroit one of the largest urban farms on the planet – which would breathe new economic life into a devastated community that desperately needs it. I also did a recent post on a University of Iowa study demonstrating that by abandoning monoculture (the practice of turning millions of acres over to the production of a single cash crop) and diversifying, produce for 10,000 people could be raised on no more than a hundred acres – and a plot the size of one Iowa county could feed most of the people in the Upper Midwest.

The fact is that despite the gloomy prophecies about how we're running out of farmland, with a combination of new technologies, judicious land management and smarter farming techniques, we can get more from less and make our cities and communities more self-sufficient: which in turn, means greater food security.

Getting back to New York City, there are three pilot projects going on showing New Yorkers how they can grow their own. One of these is a "Science Barge" that's currently moored in the Hudson River. This is actually an old grain barge that has been converted into a floating "mini-farm"/greenhouse. The Science Barge is one demonstration of how urbanites in America's largest city can grow a variety of produce without too much effort or expense. Operated by New York Sunworks, the Science Barge uses a combination of hydroponics and alternative energy to show folks how to operate a sustainable urban farming operation with virtually no waste (yes, virtually everything on the Science Barge gets recycled).

"Window Farms" are the innovation of a couple of women who live in an apartment in Brooklyn. One of the great things about this idea is that it finally provides a practical use for those obnoxious plastic soda pop bottles along with a few other odds and ends. This idea has really been catching on in the Five Boroughs, and is starting to get some traction worldwide as people add their own ideas and innovations to the concept.

Finally, there's the Eagle Street Rooftop Farm, which recently observed its first anniversary. Covering 6,000 square feet, this has actually become a profitable business, providing produce to local restaurants as well as people in the neighborhood.

If you are a big-city dweller, check them out; you may not be able to live on Green Acres, but you might be able to bring it your block.