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Green GothamWith seven billion mouths to feed, human agriculture exerts a tremendous toll on the planet, from water draws to pollution, and from energy use to habitat loss. But there is also a growing set of solutions, from organic agriculture to integrated pest management. More people around the world are taking a look at urban farming, which offers to make our food as "local" as possible. By growing what we need near where we live, we decrease the "food miles" associated with long-distance transportation. We also get the freshest produce money can buy, and we are encouraged to eat in season. Another benefit of urban farming is that it can add greenery to cities, reducing harmful runoff, increasing shading, and countering the unpleasant heat island effect. Garden plots can help people reconnect with the Earth, and gain a greater appreciation for where our food comes from (hint: not from plastic packages). Rooftop and patio gardens create peaceful places for relaxation or contemplation, and they can attract tourists—consider the booming businesses that have sprung up around New York City's lush High Line Park. And urban farming can bring jobs to underserved and depressed urban areas. Although planners have a long way to go, boosters envision soaring vertical farms that will eventually produce most of what we need within a short walk from home. Still, land in cities is often expensive, especially since gardens tend to contribute to gentrification and rising rents. Urban soils can be loaded with lead, arsenic, and other toxins, requiring remediation or replacement before planting can be done safely. Cramped conditions can limit yields, and getting enough water and sunlight can be concerns. Still, if the right combinations of new technology, community support, and economic incentives align, it's possible we may soon be munching on skyscraper scallions and avenue arugula. An early example is the rooftop garden on the InterContinental New York Barclay Hotel, which includes an apiary. The Midtown bees produce honey used in the hotel's kitchen, and they fly to pollinate plants as far as five miles away. —Brian Clark Howard (Related: Dam, Levee, and Irrigation Photos)

Photograph by Anthony Behar, Sipa Press/AP