The Oil Drum

106 comments on Death Rates and Food Prices

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Jason Bradford on January 14, 2008 - 1:22pm

Hi Sharon,
I am in full support of urban gardening and do believe that it can prevent malnutrition and perhaps keep starvation at bay in crises. I do wonder how significant small-scale gardening is calorie-wise, however.

For example, potatoes or sweet potatoes are foods that yield a lot of calories per unit area cultivated. A decent yield would be 1 lb of potatoes per square foot. Since potatoes are 350 calories per pound, this is 350 calories per square foot. A 100 sq ft garden might then yield 35000 calories. Most people would want to eat about 2500 calories per day, but can get by with less in emergencies, so let's say 1900 calories per day. That potato patch would supply the calorie needs of 1 person for 18 days under rationing conditions.

That's why I don't see urban gardens as significant for calories, but I do see them as significant for vitamins, minerals, food diversity and saving the poor $ that could be spent on staple foods and health care.

A diversity of vegetables might only have ca. 200 calories per pound, but it is rich in other ways. Vegetables are also best eaten fresh, so best to be eaten soon after harvest, which is difficult to accomplish in cities. A person may want to consume 500 lbs of fruits and veggies per year, which in a garden setting may require only 500 square feet. This would be about 100,000 calories from fruits and veggies for a year.

So yes, urban gardening is doable, valuable, and should be encouraged. But fields of grain are needed to supply enough calories to support the energy needs of a person, which is about 850,000 calories per year. And the grains need to be grown in areas that are beyond the scope of urban gardens. For example, in an intensively managed garden setting one might yield 10 lbs of grain per 100 sq ft. A person might need 300 lbs of grains per year at 1600 calories per pound to yield nearly 500,000 calories, but this would require 30 x 100 sq ft = 3000 sq ft per person, or six times the veggie area.

With heroic assumptions, including great soil, plenty of water, inputs of fertilizer, and highly skilled labor, it might be reasonable to grow enough food for a person in ca. 6000 sq ft, when paths between beds are included. That's about 1/7 th of an acre. A household would need 1/2 an acre.

I just try to keep these figures in mind because I don't want people to get the idea that they can feed themselves, and the poor can feed themselves, without access to good land, in adequate amounts, and fresh water. At the same time, I don't want to throw cold water on the necessary enthusiasm behind urban gardening/farming.

In the U.S. of course there's something like 1 acre of paving dedicated to each automobile, and there are nearly as many cars and light trucks as there are people. Room for improvement.

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jewishfarmer on January 14, 2008 - 2:31pm

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