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Marc Brazeau | Editor | Food and Farm Discussion Lab | @eatcookwrite

If I were to boil down my overall philosophy to one single, woefully inadequate bumper sticker, one version would be “Big Cities, Big Farms”. Big cities are good for the environment because of their tightly packed efficiency. It’s easy to get around on foot and by public transportation. Big, multi-unit buildings are more efficient to heat and cool. Density is great for innovation and cultural production. And on and on. Meanwhile, farms need three main inputs that nature provides more or less for free. Soil, sun and rain. It makes sense to put farms where the soil is, and where large amounts of rain and solar power can be captured at low cost. Large farms can come with all sorts of benefits for the environment. They take advantage of economies of scale, they can afford to invest in environmentally friendly infrastructure. They can afford to try out things out like different cover crops and tillage strategies on a decently sized amount of acres without literally betting the farm on them.

So I’m generally dubious towards most commercial urban agriculture that forgo these basic principles. While, I am quite bullish on urban farming that connects urban waste streams with forms of production that don’t require lots of soil, rain and sunshine – crickets or mushrooms, to give two examples of my favorite urban farming models – I remain unconvinced that rooftop farming will ever be more than a fun way to improve urban quality of life.

So, it was with a pained groan that I came across an article in WebUrbanist trumpeting “New 42,000 Sq Ft Rooftop Farm in NYC is One of World’s Largest“.

Retrofitting an existing roof, this project has turned the top of a commercial loft in Long Island City into a working urban farm with close to 1,000,000 pounds of soil supporting tens of thousands of square feet of growing space (able to produce hundreds of tons of produce annually). Efficiently designed, projects of this kind can produce food in cities with 20 times less land and 10 times less water than conventional fields.

Well, let’s start by pointing out that you can just as easily design small, intensively managed farms with supposedly 20 times the production per acres and use 10 times less water in places where you already have soil and are plugged into efficient distribution chains that won’t be adding to the traffic congestion in dense urban areas while having wage structures that make sense for vegetable production.

But beyond all that, let’s get really real. 42,000 square feet sounds like a lot of square feet. But retail and office space is measured in square feet. Farms are measured in acres and 42,000 square feet is pretty much one acre. 0.964187 acres to be exact. New York state has 7 Million acres of farm land across 36,000 farms [PDF]. I’m sorry if can’t get that excited about one really well managed acre on a rooftop.

And as you are starting to object, “But, but, but …”, before you get to that third “but” stop and ask yourself, “If this is such a great idea, why don’t supermarkets do it?” They have the roofs and they have the distribution apparatus just yards away, all teed up and ready to go. Well, a handful of supermarkets do have rooftop gardens, but they are either doing it as non-profits with volunteer labor, or with high value aquaponic crops like fresh herbs – so they have a rooftop garden to supply about 3 feet of shelf space.

I don’t have a problem with people doing this stuff, I think it’s really cool, it makes for great cities. But let’s be honest about what it means for creating a food system that really works for people and the planet. We have to move on from sexy rounding errors.

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