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It’s been 10,000 years since the agricultural revolution gave rise to cities. Agriculture now covers more than half of the world’s habitable land, and is spreading at a rate of about 15 million acres annually. Cities, meanwhile, now comprise more than half the global population (over 80 percent in developed countries), and the numbers are rising. Using current farming methods to feed a global population expected to hit 10 billion by midcentury would require adding new farmland equal in size to the continental United States.

Images: © sasaki

SUNQIAO Urban Agricultural District, designed by Sasaki for a site midway between Shanghai’s city center and its main international airport, will include a civic plaza with productive landscapes (top), a science museum, and an interactive greenhouse (bottom), among other elements.

This alarming situation is not even factoring in the impact of the climate crisis, which is expected to alter growing seasons and disrupt the phenological cycles that keep plants and their pollinators in sync. What’s more, new agricultural land mostly comes from felling biodiverse, carbon-sequestering forests to make room for mono-crops that stash very few greenhouse gases and for livestock that actually generate them. That makes the climate crisis worse, and farming more difficult.

In addition to land consumption, agriculture guzzles three-quarters of the fresh water used globally each year, while runoff from fields treated with herbicides, pesticides, and fertilizers contaminates significant amounts of the water that’s left. Then there’s transportation. As farms extend farther and farther from the cities they supply, food is trucked, shipped, and flown vast distances: farm to plate, the ingredients in a typical American meal travel an average of 1,500 miles. From a security perspective, the fact that most of the world’s food production is controlled by just a handful of corporations is unnerving. And from a public health perspective, the emergence of Covid-19 and other new diseases offers yet another indicator of ecological imbalance. It’s time to rethink the way we farm.

Food security, as defined by the United Nations, means that all people, at all times, have physical, social, and economic access to sufficient, safe, and nutritious food that serves their food preferences and dietary needs for an active and healthy life. Key to achieving food security in a way that’s more sustainable than current practices is urban agriculture—not as an outright replacement for rural farming, but as a crucial component in a balanced system.

Urban agriculture can take many forms: rooftop greenhouses, raised beds, and community-farming initiatives such as the City of Atlanta’s “Aglanta” program, which turns underused parcels in utility rights-of-way into farm plots eligible for U.S. Department of Agriculture certificates and associated loans. Ultimately, though, horizontal strategies are not productive enough to make a real dent in the food needs of a city. (If raised beds covered every rooftop in Manhattan, the produce grown would feed only about 2 percent of the borough’s population.) Just as cities grow vertically, so too must urban agriculture, and that means bringing it indoors.

“Controlled environments have been used for many years,” says Chieri Kubota, a professor of controlled environment agriculture (CEA) in the Department of Horticulture and Crop Science at Ohio State University. “Now that multiple issues are making conventional production outdoors more difficult, putting controlled environments in and near cities brings food production closer to potential markets—and also to younger generations of potential farmers who want to live in urban centers.”

Vertical agriculture is a type of CEA that—like high-rise buildings—stacks layers to provide usable area many times the footprint of the site. Instead of growing in soil, which is a heavy way to deliver nutrients, plants in vertical farms are grown hydroponically, aquaponically, or aeroponically. In hydroponics, plants are cultivated in nutrient-enriched water, which is captured and reused so that the system uses as little as a tenth of the water conventional agriculture needs. An aquaponic system pairs hydroponics with fish production, circulating the nutrients in the fish waste to feed the vegetables, and using the plants as a biofiltration system that returns clean water to the fish. Reducing water consumption even further—by as much as 98 percent, compared to field growing—aeroponic systems deliver nutrients in a fine mist to plant roots that are just hanging in the air. And because controlled environments exclude the weeds and pests that trouble field-grown produce, the use of herbicides and pesticides is all but eliminated.