James and the Giant Corn Genetics: Studying the Source Code of Nature

October 9, 2009

How viable is local food?

Filed under: agriculture,Fun With Numbers — James @ 7:21 pm

Before I begin, let me say there’s absolutely nothing wrong with supporting your local farmers through CSAs, farmers markets, or direct purchases. I’ve done similar things before and it makes sense in the same way I’d prefer to support local businesses over national chains It keeps money in the local economy and even if it didn’t, it is always more fun cheering for the home team.*

That said how viable is solely local food (usually with an arbitrary cut off of 30 or 50, or even 100 miles from its point of origin) for providing all the food for all the residents a major city?

For the purpose of these calculations we’ll assume NYC is a point but it’s actually bigger which makes this a best case situation.
18 million people in the NYC urban area, fresh off od wikipedia. A single person can subsist on half an acre, properly farmed.
That means NY needs 9 million acres of land.

For the purpose of these calculations we’ll assume NYC is single point but it’s actually bigger which makes the situation better for some people and worse for others. Approximately 18 million people live in the NYC urban area(fresh off of wikipedia). A single person can subsist somewhat comfortably on half an acre, properly farmed (And 1/30 of an acre of the RIGHT acre (meaning somewhere in the cornbelt with plenty of access to fertilizers) at the risk of serious nutrient deficiencies and the blandest diet known to man), however currently America has ~1.5 acres of cultivated land per person (The difference goes into greatly increased meat production and consumption, ethanol production, and exports.) For the purposes of this calculation we’ll use the middle number which provides a somewhat varied diet but very little animal protein.

To support 18 million New Yorkers, will therefore require 9 million acres of land or  ~14,000 square miles. Which sounds like a lot but would actually fit into an circle only 134 miles across, meaning food would have to travel a maximum of 67 miles to feed the, suddenly hypothetically fanatically pro-local food,  masses of New York City.

But wait, New York city is located on a coastline, as many major cities around the country and around the world are. So half the circle is open ocean, and therefore not suitable for the cultivation of agriculture, which means the 14000 square miles must instead fit into a half circle. Which raises the width of the circle to 188 miles (134 miles*√2) and the maximum distance food must travel to 94 miles.

And come to think of it, not all land is suitable for farming either. Of the 35 MILLION acres in the state of New York, only 7 million are currently being farmed, a mere 20% of the total. This is an underestimate of  the total amount of land that COULD be farmed as many upstate new york farms were abandoned in the face of competition from more productive land between the Appalachians and the Rockies, and later on from vegetable production in states like California and the Rockies. But I’m not going to consider the effects of bringing that land back into production as it would be less productive than that currently farmed, and would require cutting down lots of forests that have grown up over it. And I’m assuming the goal of the local food movement does not include destroying natural areas anywhere remotely near cities. So to get 14 thousand square miles of farmland in new england requires five times as much land area.

The final result is a a circle 422 miles across with food traveling up to 211 miles to reach New York City. And that still assumes no one else lives within 211 miles of NYC, which (even leaving aside the farmers to grow the crops, and the towns to provide them services) is problematic as the center of Boston (urbanized population of 4 million) lies only 215 miles to the northeast, and Philadelphia (urbanized population 5.5 million) lies <100 miles to the southeast.

Is trying to buy more locally produced food admirable? Of course! Does that mean we should plow under every field more than 50 miles outside a city limit? Absolutely not.

People are already prioritizing the things it makes the most sense to buy locally, high mass, low caloric energy items that don’t store or travel well (basically fruits and non-root vegetables). So keep buying locally! If you haven’t try it out some time. But don’t listen to anyone who implies that the success of farmers markets, urban farmers, and CSAs means we don’t have to pay attention to the plight of farmers who would have to drive hundreds of miles to meet the people they feed.

After all, to feed New York City locally food would still have to travel 211 miles and we’d have to forcibly relocate the populations of Philadelphia, Albany, and most of Boston (and then figure out how to feed all those people locally).

*I should know, I was at the ISU-Stanford women’s basketball game in the bay area. To say I was extremely outnumbered and surrounded would be, if anything, an understatement.

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