Every time I hear some breathless article about how we'll all be "urban farming" I have the urge to write a nice long post about why that's a bad idea. Fortunately, Matt Yglesias and Jeb Reed have done that so I don't have to.
First off, livestock are different from plants. A few sheep, goats or alpacas on a block would probably be okay, but I don't want to smell cows or pigs under my window, and I don't really want to hear chickens or donkeys while I'm trying to sleep.
But don't get me wrong. I'm not trying to stop anyone from raising plants in cities. My wife is cultivating an avocado grove in our kitchen, to accompany the aloe veriscaping in our living room. A neighbor has given me some great tomatoes from her window box. It's always nice to see a house with a little garden, or a community garden on a formerly abandoned plot of land. I'd rather see a farm than a parking lot. I'm all for composting, wherever the compost winds up. I don't have anything against anyone who wants to do urban gardening, even on a large scale.
I do have some problems with urban agriculture, though. They stem from the idea that it will somehow save us from global warming, pollution or some vague evil that haunts cities. This is a relatively new variant of the tired old back-to-the-land religion, combined with the "shop locally" movement, which quickly becomes absurd if taken too literally, and it doesn't really make any more sense than either of them. Yglesias says it all: we have cities for a reason, and it isn't so that we can grow acres of chard.
Bottom line: urban agriculture is not sustainable on a large scale. It will not save us from global warming, it will not provide enough fresh vegetables to cure obesity in the black population, and I can't think of any other claim that its proponents have made that passes the sniff test.
Why does it matter if the promises of urban agriculture are false? Because those false promises are used to ask for subsidies. Sometimes they're subsidies on a massive scale, like the "Hanging Gardens of Barcelona" proposal that Reed lampoons. Sometimes they're MacArthur Genius grants as described by Elizabeth Royte. And just about everything in between.
That's money that could be going to all kinds of better things, like more effective ways of fighting global warming or obesity. For example, every fifty thousand dollars spent on urban farming is at least one less bus driver (the actual number will depend on the city's labor market, collective bargaining agreement and farebox recovery ratio).
Urban farming also has the potential to be the excuse for much antisocial behavior in cities. There's going to be someone who insists on having a donkey in their backyard, but that's not the worst. I've already been chewed out for wanting to reapportion some parking spaces - by liberals who felt that they had an unquestionable right to drive in the city because of course they need the car to drive to their farm upstate! Now that they can have a farm right here in the city, every liberal can drive an SUV without criticism: you see, they need it to pick up the wood for the planting boxes, to bring the excess compost to the recycling station, blah blah blah.
You want to grow collards in your window box, or potatoes in the community garden? Be my guest. But just say no to subsidies for urban farming. Use the money for transit, or even for farms near the city. And for god's sake, don't hand people another excuse to sanctimoniously drive in the city.