There's a small but growing movement for locally-grown and even home-grown food in cities and suburbs. Some of the reasons behind this movement are aesthetic — indeed, 'vertical farming' buildings seen in recent architectural proposals can be strikingly beautiful — ecological, nutritional, recreational, and economic. Some of these reasons are unimpeachable, as gardening can be an intellectually, psychologically, and socially rewarding activity, but the economic arguments for it, which are usually the basis for the promotion of the activity as a mass endeavor, merit a closer analysis.

Home gardening as a significant food source for consumption and barter has been a regular fixture in many civilizations, and its resurgence, specially in the United States, seems to be tied to both the economic recession and the rising price of food. As the first trend has lowered wages, the application of personal time to growing food has come to appear a reasonable investment.

However, there's a significant difference between growing food as a substitute for less productive recreational activities, and growing food as a substitute for time employed at work. In the latter case, it seems unlikely that an amateur, small-scale operation can produce food more cheaply, when all costs, specially time, have been properly accounted for, than a large-scale industrial operation. In any normal situation, working an extra hour gives you the additional income to buy more or better foodstuff than you can grow in that hour.

What some proponents of local food production argue, though, is that conditions are straying from what has so far been considered normal. In particular, they point towards the possibility of high energy costs and a deteriorated infrastructure pushing transportation costs to the point where locally grown food will be economically competitive by virtue of its proximity, as well as by the reduced benefit of energy-intensive physical capital to agricultural productivity.

In the context of such an scenario (which we believe unlikely, although not impossible if the transition to large-scale renewable energy fails), it's important to note that even in the absence of cheap energy, small-scale agriculture has never been an economically efficient choice for individuals or societies. Most economic profits — and the best food — usually went to those who controlled large extents of fertile rural land, or energy sources like mills (powered by the wind or a river) or large groups of slaves.

Technology and society has, thankfully, changed since those times, but the economic lessons learned along the way remain. In an hypothetical post-oil dystopian future of very expensive energy and high transportation costs, growing food in a small garden will be less profitable, or in other terms, will lead to poorer nutrition, than owning a wind turbine or a dozen, a laboratory capable of producing antibiotics, or a network of solar-powered railroads.

We enthusiastically support green cities, but not a retreat to an economy confined to the local scale. A complex, distributed, specialized economy is, despite its larger requirements for coordination and management, immensely more effective than any collection of isolated or semi-isolated households and small communities could be, and whatever challenges we will have to face in the coming decades, we stand a better chance with more resources at our disposal, not less.