I have a bone to pick with anyone who brags that cities are sustainable because of their high density and mass transit.  Cities might be more sustainable than the suburbs or the countryside but they are not, by any measure, sustainable. That's because cities are dependent on so many imports, including food. (Believe it or not, an architect once chastised me for saying this in a public forum.)

A city cannot be truly sustainable until it becomes less dependent on the outside world. This includes incorporating agriculture in a systematic way. But most cities have rules against urban agriculture on public land and against the harvesting of food—picking fruit from trees, for example—on public lands. In New York City, I'm told it is against the rules to plant fruit-bearing trees in public parks and against the rules to pick fruit from any park trees, for example.

Somehow, the image of the fox salivating over the grapes in the Aesop's Fable springs to mind. Except, this time, the fox gets a bunch of grapes and then gets hauled off to jail while the grapes rot on the ground!

Urban agriculture is a thorny issue. So many things have to be done to make it happen, including changing the rules.  Urban farm cooperatives—such as the idea of linear farms running between the opposing back yards of brownstone-lined city streets—run into issues of property ownership. There might even be a hesitation on the part of the city and potential private urban farmers because of liability concerns. What if someone gets sick eating the fruit or the vegetables and sues?

There are so many reasons not to move ahead. But there is an overarching reason to ignore the obstacles.

Imagine my delight, then, when I learned that architect-planner Andres Duany, aka Mr. New Urbanism, has thrown his considerable zeal behind agricultural urbanism. Recently, Andres gave a talk on the subject to the architecture and landscape architecture students at City College in Upper Manhattan.

Andres and his partner Elizabeth Plater-Zyberk—the dynamic duo of new urbanism—beat back formidable zoning and other barriers that eventually transformed town planning. Today, compact, walkable and transit-oriented communities are mainstream. With Andres and Elizabeth on the side of urban farms, they might even happen!

Examples of agriburbia, as it has been called, or "ag urbanism," are few and far between. Serenbe is one project in Georgia that is way ahead of the pack. The planned Southlands, in Western Canada—designed by Andres and Elizabeth's firm, DPZ—is in the approvals stage. Infrastructure work for the planned community of Bishops Bay, near Madison, Wisc., is scheduled to get under way in the spring. But the planned linear farm cooperative between  opposing back yards is not happening until a later stage. That makes me wonder whether the farm will ever happen.

As with new urbanism in its infancy,  planning commissions, real estate developers and even possibly buyers are wary of such a radical idea as a farm cooperative. Most people are a lot more comfortable with golf communities! (There are actually "sustainable" golf courses—with bioswales and stormwater control systems. (Sustainable golf courses. An oxymoron!)

The good news is that if anyone can rally support for and popularize the idea of ag urbanism, it is Andres Duany. So, if he is on a campaign for urban agriculture, there might be hope. In any case, he has planted the seed in the minds of at least one group of architecture and landscape architecture students. Who knows what might grow from that.