Assume enough bombs have been dropped for there to be a nuclear winter which would impede the growing of crops and cause famine. Modern infrastructure in most major nations has collapsed, and all the combined deaths from the aftereffects (fallout, societal breakdown, and the aforementioned famine) are expected to reach at least two billion.

In one of the countries most affected, like the United States, what's the largest settlement that could continue functioning indefinitely after the war? I highly doubt any major cities would remain after a few years, but what about towns, villages and hamlets? Could smaller settlements find a way to survive? If so, what do you think would be the maximum sustainable population when modern amenities are gone and the people are living off scavenged pre-packaged food and subsistence agriculture in the middle of a nuclear winter?

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    $\begingroup$ Cities with millions of inhabitants existed before 1900, fed by coal-powered railways and waterways from agriculture far away. Which of these cities were not bombed during your nuclear war? Refugees flee...but will probably return to unbombed cities as the postwar economy takes shape and banks and factories and hospitals and universities restart. $\endgroup$
    – user535733
    Jul 11, 2017 at 16:30
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    $\begingroup$ There are two factors that we need to assess here: radioactive fallout and degree of cooling. If the city is affected by radiation, it's population, while initially high, would be sick and dying not much later. For the cooling, are we talking 1-2 degrees C for one year, or 10+ degrees C for 10+ years? One year survival would be primarily dependent on food storage and not agriculture. In 10 years, situation may turn to a completely opposite one. $\endgroup$
    – Alexander
    Jul 11, 2017 at 17:34

5 Answers 5


According to an answer to a previous question, it is possible to support one person per 800 $m^2$. Converting that to square kilometers, we get 1250 people. Converting to square miles, about 3200 people. Roughly half the world's land is used for farming, as per National Geographic. So cut that down to 1600 people. Let's assume that the original estimate was generous. We have 1000 people per square mile.

Assuming people have to walk to their farms from a central, fortified town, that gives us a community size with a three mile radius or roughly twenty-eight square miles. This is because it takes about an hour to walk three miles. And a daily commute length of an hour each way is feasible. So roughly 28,000 people in the community.

This gives us an upper community size of 28,000. To support a larger community, it would need to trade with smaller communities. It would have to offer something for which people would trade food that they couldn't just build themselves. And it would have to be something that they would need continuously. Otherwise the large community would starve as soon as it ran out of communities with whom to trade.

Some communities may be able to survive longer if they are powered by nuclear or renewable fuels and have access to stored frozen food. But that won't work perpetually. Eventually the food stores will run out. For longer term survival, they need to find new food sources.

The same problem applies with scavenging food. That can work for the first year or two, but after that the food will have spoiled. Certainly anything that is served fresh. But even things that are canned will run out eventually. If you wait long enough, the cans will fail. They can rupture after getting too hot or too cold. Or the steel rusts away.

Post-apocalypse survival favors small, distributed communities over large central communities. For defensive purposes, a three mile radius might be too large. If it takes an hour of hard marching to respond to an attack, then attackers can do significant damage to the crops before being repelled.

  • $\begingroup$ 1. 800 square meters per person is very optimistic and isn’t taking into account nuclear winters, radiation, lack of chemical fertilizer, etc. 2. A square kilometer is bigger than a square mile. You did the math backwards. 3. What does half the world’s land being used for farming have to do with anything? Isn’t the community built on arable land? 4. Why wouldn’t people live on their own farmland so they don’t have to walk hours to their farms? 5. Large communities always rely on trade with outlying communities, it’s how cities of hundreds of thousands have existed for thousands of years. $\endgroup$ Jul 11, 2017 at 21:36
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    $\begingroup$ @MikeNichols A mile is longer than a kilometer, about 60% longer. Each square mile is about 2.6 square kilometers. You say that 800 is too optimistic and then complain that half is too pessimistic. Those kind of things cancel out. You don't live on your farm because you can't defend 27 $\text{mi}^2$, but you can defend a small town. And you can't rebuild trade immediately after an apocalypse. You don't have high tech resources because the big cities were destroyed. No ports for shipping oil and coal. You don't have low tech solutions because we abandoned them for high tech. $\endgroup$
    – Brythan
    Jul 11, 2017 at 21:53
  • $\begingroup$ @Mike Nichols A square kilometer is bigger than a square mile? I get 1250 and 3237 respectively for his numbers. Also, he used the fact that half of the land is used for farming to calculate the area needed to sustain the amount of people he was considering. I do agree HOW that land is distributed is up for debate, but I also argue that in a nuclear winter, they would probably need MORE land to grow anything, but I'm not a botanist. Maybe there is a low light plant capable of supporting human life? $\endgroup$
    – ozone
    Jul 11, 2017 at 22:00
  • $\begingroup$ @Brythan Completely right about miles and kilometers. No idea what my brain was doing. Half the world being used for farming has no relation to whether half the land in a given area can be used for farming. It's simply completely unrelated. Small indefensible communities exist despite hostile environments. Generally an army is used to protect them. Animal and person powered carts were used to transport food and other goods to support cities of hundreds of thousands 2000 years ago. Carts aren't hard to fashion, in fact we would have lots of spare wheels and a fantastic road infrastructure. $\endgroup$ Jul 11, 2017 at 22:11
  • $\begingroup$ @MikeNichols Carts are easy, but they don't magnify the daily distance. Animals are tougher. We don't raise large numbers of draft animals these days. Yes, there are some, but not enough to support large communities and not in the right places. Give it a hundred years and that would change. But in the near term, it wouldn't work. And even if they did, why would the farmers give their product to the city? What does the city offer them? We can argue about how much land is arable, but even on a farm, not all land is available. Think forest, stream, hills, roads, buildings, etc. $\endgroup$
    – Brythan
    Jul 11, 2017 at 22:37

I don't think I could give you a figure, but assume I was a general in the army and I had a a thousand of soldiers to look after.

Many supermarkets have large storage facilities for the food they sell. I would send scouts to the nearest and then attack and displace any other scavengers. (We take this Sam's Club for the glory of the nation). Once food is secure for a few months, I'd send scout parties looking for professionals: doctors, engineers, and nuclear physicists. I would offer them and their families safety and food in exchange for their services.

The next and harder part is to get the energy. Many wind mills might work after the nuclear disasters and I could use them to power my new settlement to some extent. If I find a few decent engineers to help with that, it should be a piece of cake. If not, we'll keep raiding the nearby university libraries in search for PhD students who didn't get the memo that there was a nuclear disaster. If I can get nuclear engineers and physicists, and especially if I can find a nuclear plant that hasn't been destroyed in the attack, I could try restarting it. It might not be trivial with all the infrastructure destruction, but my scientists could find a solution and I could enslave a bunch of people to help me build the missing parts.

Once the abundant source of energy is found, we could raid seed banks, or even get seeds from Walmart and grow plants the way Lt. Smith used to grow pot under UV light in his apartment in LA. Some agricultural engineers could help us with that. Even if nuclear energy is not available, and the oil, gas and wind energy we can scavenge is not enough for this type of farming, we can grow mushrooms (portobello, pleurotus), and some plants that don't need too much sunlight, like ferns. We can get our farm animals (goats) to eat these plants, and we will thrive on meat and mushrooms. We can also farm dogs since the dog food from the supermarket will last us for a while. The best dogs will be attack dogs, while the rest will be tasty.

The size of the colony will depend a lot on how soon we secure access to food, energy and trained personnel. I think three thousand of people should be the order of magnitude for the colony. There should be minimum 100 soldiers available at any time for raids, and about a thousand for defense, especially from other organized groups. With three thousand people, the colony will last long enough, until the nuclear winter ends.

  • $\begingroup$ I'm not positive, but I think when a nuclear power plant goes black long enough, it melts down. But I think other power plants could be restarted. $\endgroup$
    – ozone
    Jul 11, 2017 at 22:10
  • $\begingroup$ That is what made me think of coal and oil. I forgot gas but those will be around for years even with a nuclear war. $\endgroup$
    – chaiboy
    Jul 11, 2017 at 22:52
  • $\begingroup$ wow here is a play by play of what a reactor would do if abandoned. quora.com/… $\endgroup$
    – chaiboy
    Jul 11, 2017 at 22:55

I'm thinking your most successful settlements are going to be in very rural areas, like the southern reaches of the grain belt in the US and maybe similar latitudes in parts of Asia, like the steppe or maybe the Ukraine. Here is why:

In the US there will be Farms. Well maintained farmland. There are a lot of small family farms as well as the big corporate types. That means you will have knowledge of how to work the land.

In the Family Farms, there is a pretty high probability that there will at least some livestock that can be bred from as well as used for draft animals. Also, in plenty of places you might find older but still functional tools and basic machinery. This machinery will help keep things going, and won't require refined fuels. Horse collars, hand plows, 2 man saws. Tack and saddles will be readily available.

Preppers! This is only slightly a joke. I watched part of that Preppers show on TV and most of them lived in rural communities with only a few exceptions. A lot of them have researched a lot of techniques for survival when the excrement hits the rotating blades. this is going to expand the knowledge base somewhat. Food Preparation gets a boost here.

There are also greenhouses of various sizes dotting the landscape here and there dotting the landscape. This will be a huge help with the coming Nuclear winter. there will hopefully be enough time to build more greenhouses. To heat the greenhouses, there should be plenty of fuel in the forms of rows of windbreak trees and such.

It's a good start to keep groups going for several years. The Ukraine has areas similar in soil composition as Kansas, so as long as the people get together as I suspect they would here.


I am in the middle of working on a post-apocalyptic game so I had to work out some of this stuff already. Here's what I found. I think it is a matter of power and radiation. If you go up into coal country I am sure that you can keep those power plants running throughout the nuclear winter, same with gas country. Coal mines and oil wells are common enough that plenty should survive a war. Hell downtown LA has oil rigs disguised inside of plenty of buildings so they could find a way to refine it and power generators. So you could have groups built around those pumps and the what they do with it.


Yes, some of these groups could be heavily radiated if the bombs feel near by. They may die young but still produce power that can be used by other groups.

So once you have power you can build greenhouses and produce food. So if the story takes place early enough then there may not be any major communities. Two or three years out as they get the food production stabilized the communities surrounding it will begin to prosper.

The locations will most likely run by a warlord or some other kind of armed organization that can keep the locations safe enough for work to get done.

Check out these links with articles on indoor farming. New Jersey already has one in an old factory. Metal and concrete structures would be great at block out radiation.


Clean water would be the next hurdle If that can be found along with power and the people to put it all together then you could have a few clean healthy towns. If they get big enough they may try to expand out and take over other communities. That is if this takes place far enough in the future for the communities to have a large population.

Radiation would be really bad for any kind of community. Children will have too many debilitating birth defects, many mental to allow the community to survive so if power is in a radiation zone then maybe only the old are sent to work there since they would never live long enough to be debilitated by it and, of course, would not be having kids so that isn't a problem.

Now if you are talking about scavenging then areas that are not hit would run out of all food pretty quickly as everyone hordes any food they can reach. So anyone that came later would have to break into houses to find caches or raid them if people are still there. The only place they could find untouched food would be in the ruins of the nuked cities.

Maybe an organized team could send teams in to retrieve salvageable food. The dishonest may go and grab anything they can find and sell it as normal foodstuff. A Geiger counter is a must have item when shopping.

So in early days lots of people trying to gather the stuff to survive and build some kind of life support and in later days communities emerging around greenhouse farms and finally cities built around those same communities and even expanding to take over old areas.


Start with a city with a major role in the food processing industry, like Enid, Oklahoma which is home to the third largest grain storage facility in the world. Now assume that by dumb luck this city was not be targeted for direct nuclear attack, (despite its proximity to Vance Air Force Base and Oklahoma City).

The 50,000+ residents of Enid would be in comparatively good shape to survive a nuclear winter. Pre-war Oklahoma winters are brutal enough that the residents already know how to deal with the cold. Chances are they could selectively take in refugees from the surrounding area, swelling their manpower to a quarter million without seriously taxing their food supply. With that much skilled labor, the city could quickly be fortified and then they could ride out the long cold storm.

It is admittedly an optimistic guess, but with its food reserves, Enid might be the strongest survivor in a nuclear winter scenario.


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