All the World's a City

Is skyfarming the wave of the future?

After last month's fascinating article comparing London and New York, New York Magazine does it again with another mind-opening story on "vertical farms." That is, using skyscrapers as centers of agriculture.
The NY Mag article cites Columbia professor Dr. Dickson Despommier, who says within 10-15 years a "supergreen," 30-story skyscraper could be built that produces fruit, vegetables, and grains while generating clean energy and purifying waste water. He figures 150 such vertical farms could feed the population of New York City proper (~8 million people), about 55,000 people fed per building.
(Similar ideas have long been proferred by advocates of space exploration, who have done endless calculations to prove that giant space stations could grow and feed city-sized populations in orbit around the Earth.)
That's a lot of construction, but according to Emporis, NYC currently has 5,560 high-rise buildings within its 800 square kilometers of land area. And 120 more are under construction, with 120 in the planning stages.
The professor says vertical farming would be able to feed the estimated 9.3 billion people expected to populate Earth in 2050, without using up more land area.The magazine suggests that the land requirements to feed the increase in world population (which now stands at about 6.2 billion) will require cultivation of a landmass area as large as Brazil." And with an estimated 80% of the world's population expected to live in urban areas by 2050, which works out to 7.3 billion citydwellers, why not grow agriculture where it is consumed? GEO