During the medieval age, one of the main reasons that pushed besieged cities to capitulate was the exhaustion of provisions (foods,water,drugs...) that maintain the every-day life of the city population.

I wonder to what extent could a city generate its own resources by harnessing the little bit of available room and creating farms, small factories and recycling, thus avoiding famine, plague and acquiring what could spare souls...

I konow that someones may argue that there is not enough space to create farms or factories but cities like Byzantium or Cairo were huge and have enough room for that.

Are there any known cities that have been through such an experience, enduring sieges, or was the only hope to smuggle provisions through the enemy lines?

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    depends on the city, but take Antioch for example, its size is approximately 1100 acres. Its population was anywhere between 100k and 400k. Assuming the entire city was nothing but fields for planting, you would have .01 acres per person. A person needs at min .5 acres of prime agriculture land to survive. So no, even if they turned over the entire city into a farm it would not supply enough food. – ed.hank Feb 13 '20 at 23:03
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    This question would benefit from preliminary research. Few cities could feed themselves in normal circumstances. When the farming population of the surrounding countryside flees within the walls it further strains supplies. – MCW Feb 14 '20 at 0:24
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    @Mark C. Wallace: I'd change "few" to "no". It's an inescapable part of being a city, rather than a fairly dense rural area. Even as late as WWII, Britain imported a large part of its food, and the Germans hoped to starve the British into surrendering with its naval attacks on merchant ships. – jamesqf Feb 14 '20 at 2:40
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    @gerrit: No, that's false. On a vegan diet the people would rapidly develop sever health problems from the absence of the supplements needed to remain healthy on a vegan diet. There's a reason the full cost of eating vegan is greater than eating a normal healthy diet including meat. Britain also has a large area of pasture land unsuitable for any agriculture besides livestock and dairy. Same reason why no third world countries eat vegan - far more expensive than otherwise. – Pieter Geerkens Feb 14 '20 at 11:36
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    Before the black death, England was right at the carrying capacity of the land using medieval methods. Peasant diets were low-meat due to this. Eggs and diary were common because those were good ways to convert non-edible plant material into food, while pigs were used because they also were good at converting food waste and non-edible material found in forests into calories. @Pieter Geerken's point about land unsuitable for food production is important, and it's the reason why there have been vegetarian societies, but not vegan ones. – Gort the Robot Feb 14 '20 at 17:42

No. Cities were simply too small physically to feed themselves. Constantinople was one of the biggest cities of its time, at 2.3 sq miles. This works out to around 1500 acres. To feed a single person you need, at minimum 6-8 acres of land. This means that if the entire area of the city were farmland, it would feed at best around 250 people.

Even with modern farming methods, you would need just under 1/2 acre per person. That still puts you at only around 3000 people.

Using extreme techniques, some people claim to be able to do as well as even 20 people per acre. This requires a large investment in modern technological produces like drip irrigation, and assumes access to electricity and running water. If we took this number, and applied it to Constantinople, we would get roughly 30,000 people fed. (Assuming you could do it at this scale, which no one has even done in modern times.)

Constantinople had on the order of a half million people, which puts it at around 350 people per acre. So yeah, this is just entirely unworkable even with modern techniques.

  • If this is the case, how could some cities survive decade long sieges? Although rare, such things did happen even in ancient times. I would guess blockade runners, smuggling in resupply once in a while when the encirclement was less than perfect (or through secret tunnels?), or maybe even sorties and raids, looting supplies and then hurrying back behind the walls before the besiegers could mobilize. – vsz Feb 14 '20 at 15:49
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    @vsz They survived for years because the sieges were incomplete. The besieging force was on land and the sieged city had a harbour, for example. – Kakturus Feb 14 '20 at 17:02
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    @user560822 Modern techniques aren't relevant to the question. Note that that page assumes access to electricity and running water. Even so, the population density of Constantinople was 340 people per acre, so even if you accept being able to feed 20 people from an acre of land, you are still an order of magnitude short. (Medieval urban population densities greatly exceeded that of modern cities) – Gort the Robot Feb 14 '20 at 19:24
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    Medieval societies had no way to produce fertilization via nitrogen fixing. That is the core reason for that great increase of availability. – Gort the Robot Feb 14 '20 at 20:58
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    @user560822 - did you even read the link you posted, it shows that it requires basically 2 acres to feed a family of 4, see the handy infographic at the bottom. And again this is assuming modern techniques. Also in both mine and Gorts calculations we assume the entire city is a farm and that land is productive, when in reality at most 50-60% that space could be used for farming, i mean people need to live somewhere right, they need roads, etc... So still the answer is a resounding NO a city could not self-sustain itself in a siege. Also corn did not exist in medieval europe. – ed.hank Feb 14 '20 at 22:38

As answered in comments and by Gort, there is zero chance of this happening by growing crops. It's not just the space that's insufficient, it's the complete and utter lack of soil.

The one workaround involves 2 things:

  • Exploitation of all available food sources.
  • Drastic reduction of population.
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    I'm not sure if reducing population from 30,000 to 400 by cannibalism and then surrendering counts as a workaround... – gerrit Feb 14 '20 at 11:17
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    @gerrit: There is the further problem that the food source vastly outnumbers the garrison determined to consume said food source, and the obvious end-game starkly follows Niemöller's Law: "First they came for the really fat people, and I did not speak out — because I was not a really fat person. Then they came for the modestly fat people, and I did not speak out because I was not modestly fat. Then they came for the average-weight people, and I did not speak out because I was merely thin. ...." – Pieter Geerkens Feb 14 '20 at 11:30
  • At the siege of Alesia they considered cannibalism, luckily in the end they only kicked out all of the citizens out of the city and left them to starve in no-mans land. – ed.hank Feb 14 '20 at 13:13
  • Drastically reducing your population is defeating the purpose of the whole siege business. You go behind the walls to protect yourself. And you stay there to fight back. It is like committing mass suicide on the battlefield to prevent a battle. – Greg Feb 14 '20 at 20:00
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    @Greg Was the Monty Python reference intentional? – Peter Feb 14 '20 at 20:10

If people could grow enough food in cities, then they wouldn't have farms, they would just have cities.

Even modern farms would not be able to supply enough food, and they are far from self-sufficient. They are heavily dependent on water and fossil fuels.

And your title is a bit misleading; "economy" refers to the management of resources, not its production (although production of resources is a factor in economies). One can't stop a population from starving just by passing money around.

  • +1 for the first sentence – ed.hank Feb 14 '20 at 23:27

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