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How Many People Can The Plants In One City Feed?

The Collectors: Food cartographers


The locavore movement has been in vogue long enough that it has an app and a listicle on PBS. Locavore was even the word of the year way back in 2007. But what does it mean to eat local when you live in a city? How many people can truly be fed locally in a densely populated urban environment?

Last week, FiveThirtyEight and ESPN Films published the first in a series of short documentaries called The Collectors, profiles of people who use data in innovative ways. “Cartographers of the Edible World” introduced Ethan Welty and Caleb Phillips, who built an open-source, user-generated website that catalogs the location of edible plants all over the world. When the two men met, Phillips was interested in technology for social organizing. Welty was using publicly available data to map arable land. They both had maps for personal use that helped them forage food from city parks and public spaces in Boulder, Colorado, where they live.

Their website, Falling Fruit, has more than 786,000 data points, each of which represents a location containing one or more plants. What’s remarkable about the site is that 98 percent of the data points currently come from municipal tree inventories. When Welty was calculating the arable land in Boulder to determine how many people could be fed through urban agriculture, he used these tree inventories to subtract where trees are located, since planting in an area shaded by a tree is fairly useless. But then he realized a lot of those trees had edible components.

Many cities keep tree data in order to care for the plants, according to Welty and Phillips, and more and more cities are making that data publicly available. Welty says this is a perfect example of why open data is so important. “You never know what people will think of,” he told me. He and Phillips have nearly 50 tree inventory data sets already on the site, but there’s a backlog waiting to be uploaded. They are also limited by language: Welty speaks French and English and he knows the right words in Spanish and German to put inventories onto the site, but data in other languages is currently inaccessible.

The rest of the data comes from a variety of online sources and individual users. It’s a wiki, so anyone can add data points about anything. Water fountains, Eastern grey squirrels in an area where they are invasive, and doughnut crumbs marking the outside of a police station all have been added to the site (the latter pushed the limits of what the founders allow on the site, though Phillips was fascinated that someone would use it for “political signaling”).

Both men are quick to say it isn’t possible to feed all city dwellers on urban foraging alone. The conclusion of Welty’s Boulder study is that residents could get their produce from urban agriculture five to six months a year. A more conservative study of New York state by researchers at Cornell University found that at best, only 1 in 5 residents could eat from food grown exclusively within the state. The New York study also found a fivefold difference in capacity depending on what people eat; the number of people who could be fed with a daily diet of 2,300 calories changed dramatically with different balances of carbs, dairy and proteins. (It’s worth noting that a plant-based diet was not the most efficient use of space. Crops can’t grow year round on much of the land in New York, and high-fat animal proteins provide for more calories, making beef a more efficient use of space in several parts of the state. A vegan diet did not support the maximum number of people in New York.)

Phillips and Welty would like to expand Falling Fruit to include information on when fruit is ripe (using climate data, most likely), and they are currently creating a mobile version of the site. But my favorite detail is that they considered umwelt when they built Falling Fruit: A secret URL shows the data from the perspective of pollinators, mapping clover, linden and other plants that honeybees like to frequent.

CORRECTION (Dec. 17, 4:57 p.m.): An earlier version of this post misstated the name of one of the men behind the Falling Fruit website. His name is Ethan Welty, not Evan.

Anna Maria Barry-Jester is a senior reporter at Kaiser Health News and California Healthline, and formerly a reporter for FiveThirtyEight.