Apologies if I wasn't being clear - I am not claiming that urban areas can be self-sufficient in food, or that calorie crops produced on a larger scale are not essential - merely that, for example, those 18 days worth of calories can make the difference between starving to death and mere malnutrition - or between malnutrition and a barely adequate diet. My mention of staple vegetables was simply to observe that the idea that vegetables provide minimal calories is not always correct. Let's imagine a 200 square foot plot for a family of four, for example. Such a plot, intensively managed, could produce enough dense calories for, say four or five full days of additional survival, or more likely, 10 or 12 days of marginal survival. That's a big contribution to the yearly diet for a person suffering from malnutrition. Then add flavorings, nutritious greens, some leguminous protein crops a couple of chickens running around for eggs, fat and proteins, fed mostly on weeds, scraps and garden wastes. There are probably two full weeks of survival no one has to pay for (amortized over the course of the year) plus supplemental nutrition. Given that the majority of the world's poor spend 70% or more of their income on food, 2 weeks of not buying food is an enormous difference in their lives - think about how large a percentage of your income 2 weeks salary that can now be applied directly to future food purchases would (not a perfect analogy, I know).

Again, it isn't my claim that people can live on 100 or 150 square feet - far from it. But gardens in fairly small spaces can make a critical difference in diets, providing a margin for survival. Nor am I claiming that this will keep billions people who are being systematically starved alive - far from it. Merely that any analysis of the mitigating factors might wish to include the nutritional and caloric content of garden production.

It is also useful to think about the aggregate effects of such gardens - for example, Michael Hamm and Monique Baron have calculated that 3 million 200 square foot gardens in the state of New Jersey, *plus* existing farmland* would be sufficient to feed the state - if the gardens were planted into appropriately nutritious crops. That is, such a 200 square foot garden won't feed a person for a year, but the supplemental value does dramatically reduce the total amount of arable land required to feed a given region. Does this make sense? That is, gardens do not function as simply "supplemental, uncounted" calories - they produce some tiny percentage of needed calories, which added up on large enough scale, makes a huge dent in the practicalities of needed farmland.

There are number of fascinating analyses of this data in Koc, McRae et als _For Hunger Proof Cities_. But your larger point stands - no one is going to be producing all their food on a rooftop, and we will all need calorie crop production. Cuba kept importing rice, and Russia kept growing and importing wheat during the worst of their crises. But I think there's at least as great a tendency to underestimate the potential of small scale food production as there is to overestimate it.

Sharon