Urban farming could yield up to 10 % of many food crops, says new research

Urban farming could yield up to 10% of many food crops, says new research

Gotham Greens’ boxed lettuces have been popping up on the shelves of high-end grocers in New York and the Upper Midwest since 2009, and with names like “Windy City Crunch,” “Queens Crisp,” and “Blooming Brooklyn Iceberg,” it’s clear the company is selling a story as much as it is selling salad.

Boxed lettuces are already being grown in hydroponic greenhouses on the rooftops of buildings in New York and Chicago. The greens are shipped to nearby stores and restaurants within hours of being harvested. That means a fresher product, less spoilage, and lower transportation emissions than a similar rural operation might have—plus, for the customer, the warm feeling of participating in a local food web.

Although cities and states have begun to loosen restrictions on urban agriculture, and even to encourage it with financial incentives, it has remained an open question whether growing food in cities is ultimately going to make them greener.

Will the amount of food produced be worth the tradeoffs? A recent analysis of urban agriculture’s global potential, published in the journal Earth’s Future, has taken a big step toward an answer—and the news looks good for urban farming.

“Not only could urban agriculture account for several percent of global food production, but there are added co-benefits beyond that, and beyond the social impacts,” said Matei Georgescu, a professor of geographical sciences and urban planning at Arizona State University and a co-author of the study, along with other researchers at Arizona State, Google, China’s Tsinghua University, the University of California, Berkeley, and the University of Hawaii.

10% of global output

The researchers determined that, if fully implemented in cities around the world, urban agriculture could produce as much as 180 million metric tons of food a year—perhaps 10 percent of the global output of legumes, roots and tubers, and vegetable crops.

The study also looks at “ecosystem services” associated with urban agriculture, including reduction of the urban heat-island effect, avoided stormwater runoff, nitrogen fixation, pest control, and energy savings. Taken together, these additional benefits make urban agriculture worth as much as $160 billion annually around the globe. The concept of ecosystem services has been around for decades, but it is growing in popularity as a way to account, in economic terms, for the benefits that humans gain from healthy ecosystems. Georgescu and his collaborators decided to investigate the potential ecosystem services that could be provided through widespread adoption of urban agriculture, something that had not been attempted before.

The team began with satellite imagery, using pre-existing analyses to determine which pixels in the images were likely to represent vegetation and urban infrastructure. Looking at existing vegetation in cities (it can be difficult to determine, from satellite imagery, what’s a park and what’s a farm), as well as suitable roofs, vacant land, and potential locations for vertical farms, they created a system for analyzing the benefits of so-called “natural capital”—here, that means soil and plants—on a global and country-wide scale.

Energy saving

Beyond the benefits we already enjoy from having street trees and parks in our cities, the researchers estimated that fully-realized urban agriculture could provide as much as 15 billion kilowatt hours of annual energy savings worldwide—equivalent to nearly half the power generated by solar panels in the U.S. It could also sequester up to 170,000 tons of nitrogen and prevent as much as 57 billion cubic meters of stormwater runoff, a major source of pollution in rivers and streams.

“Urban agriculture will never feed the world … but the important point is that natural capital in cities can be vastly improved,” said Robert Costanza, a professor of public policy at Australian National University, cofounder of the International Society for Ecological Economics and researches sustainable urbanism and the economic relationship between humans and our environment.

Costanza said he would like to see the researchers’ big data approach become standard in urban planning, as a way to determine the best balance between urban infrastructure and green space—whether it’s farms, forests, parks, or wetlands. That is the researchers’ hope as well, and they’ve released their code to allow other scientists and urban planners to run their own data, especially at the local level.

While the researchers don’t believe that urban farming is ever going to replace more conventional farming it can play a role in bringing people closer to their food, and in making our cities more diverse and interesting and green.

Further information

May 11, 2018
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