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Urban farms could be incredibly efficient—but aren't yet

In some ways, hyper-local food is a counterculture movement, focused on growing herbs and vegetables in the same dense urban environments where they will be eaten. It trades the huge efficiencies of modern agriculture for large savings in transportation and storage costs. But is urban farming environmentally friendly?

According to researchers at Australia's University of New England, the answer is pretty complex. Within their somewhat limited group of gardeners, urban agriculture is far more productive for the amount of land used but isn't especially efficient with labor and materials use. But the materials issue could be solved, and the labor inefficiency may be a product of the fact that most urban farmers are hobbyists and are doing it for fun.

The researchers—Robert McDougalla, Paul Kristiansena, and Romina Rader—defined urban agriculture as taking place within a kilometer of a densely built environment. Working in the Sydney area, they were able to find 13 urban farmers who were willing to keep detailed logs of their activity for an entire year. Labor and materials costs were tracked, as was the value of the produce it helped create. The energetic costs of the materials and labor were also calculated in order to assess the sustainability of urban farming.

The plots cultivated by these farmers were quite small, with the median only a bit over 10 square meters. Yet they were extremely productive, with a mean of just under six kilograms of produce for each of those square meters. That's about twice as productive as a typical Australian vegetable farm, although the output range of the urban farms was huge—everything from slightly below large farm productivity to five times as productive.

For the vast majority of crops, however, the urban farms weren't especially effective. They required far more labor than traditional farms, and, as a result, the total value of the inputs into the crop exceeded the income from selling it. In other words, the urban farmers were losing money, at least by traditional accounting measures.

PNAS, 2018. DOI: 10.1073/pnas.1809707115  (About DOIs).

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