Let's pretend that somewhere around our current time there exists a secret superweapon that kills humans nearly instantly but doesn't cause significant damage to structures or nature (flora and fauna). And it is used globally. At the same time, there is a secret defense initiative that installed shields in major cities. Let's say, the cities with population of 2+ million people. In Europe these are Istanbul, Moscow, London, St.Petersburg, Berlin, Madrid, Rome, Kiev and Paris.

So, everybody outside these cities die. What will happen with the city folks? Will they die of hunger, because they lose agricultural import from rural areas? Or do they have the capacity to restore the food supply? Or maybe even create food supply within the city? And will they be able to spread their population to the empty lands (there is no radiation, just damaged structures and wilderness) or will they become closed city states?

  • $\begingroup$ Reference: Caves of Steel from Isaac Asimov. $\endgroup$ – mg30rg Jan 29 '16 at 11:05
  • $\begingroup$ How does something kill humans instantly but not any fauna? Is it a Kingsman head-splodey thing? $\endgroup$ – Azor Ahai Jan 30 '16 at 0:41

The biggest problem would be the potential societal/governmental breakdown this could cause. For example, many capital cities have less than 2 million population. The destruction of much of the world's government would most likely be catastrophic and lead to unrest in which nothing (including agricultural production) was working properly. This would, indeed, likely lead to starvation, as well as death for reasons such as war. Only a fraction of the population would survive.

However, anywhere that reasonable institutional stability remained, it would probably be possible to avoid significant starvation.

Consider the following facts:

The world population (and therefore its food requirement) has just dropped dramatically, lowering the food requirement. The world is about 50% urbanized, but a much smaller portion live in cities over 2 million people. Based on this list, I would guess this would leave a population of perhaps 1-1.5 billion.

There is a fairly large supply of existing food, from cans on supermarket shelves to strategic grain reserves to livestock that can be slaughtered and eaten. It is hard to estimate this, but I would expect the population to be able to survive for a few months on existing food. This would allow agricultural operations to resume.

Getting farms back operational would be a significant, but solvable problem. There will be some people with farm experience in the cities, though not enough to operate very many farms. It would be necessary to train people to get things operating as quickly as possible.

Expertise is certainly needed to run a farm, but much of the actual labor involved is fairly simple and could be learned quickly. A system could probably be devised where the top experts travel between farms and give high-level advice, while those with more limited experience train others how to do things like operate equipment.

There certainly would be major losses in productivity, for several reasons:

  • A gap of even a few weeks where a farm is unattended would damage some crops.
  • Some farms would be mismanaged due to the lack of expertise.
  • The supporting infrastructure for farms (e.g. tractor repair, fertilizer supply, etc.) is probably largely rural and may be harder to replace.
  • Other, more general infrastructure, like fuel supplies, would be hard hit as well.

However, given that the food yield only has to support less than a quarter of the previous population, I don't think these problems would be big enough to cause starvation.

  • $\begingroup$ The lack of fertilizer alone would reduce the output of farms by some 75%. Add the lack of tractors (no fuel), and on top of that the lack of skilled farmers. $\endgroup$ – Burki Jan 29 '16 at 10:46
  • $\begingroup$ @Burki, but the first year there would be fertilizer still around and some fields would be already fertilized. Also, some fertilizer production could be restored, while natural methods (e.g. manure) require less expertise. The lack of mechanisation could be compensated for with manual labor. In the U.S. for example, <2% of the labor force are farm workers, so there is plenty of room to make up for loss of productivity with more farm workers. Of course, there would be a catastrophic drop in the standard of living but in the event that a stable government survived, I don't see starvation. $\endgroup$ – user16107 Jan 29 '16 at 10:52
  • $\begingroup$ I doubt that your thoughts hold up. Modern society relies heavily on modern society to funktion. When you take away important bits, the rest quickly crumbles. The first thing you will get is anarchy. After that, things will get interesting. $\endgroup$ – Burki Jan 29 '16 at 10:55
  • $\begingroup$ @Burki, this is certainly highly speculative since nothing like this has ever happened. I do think anarchy is the most likely possibility (as I stated). My point is just that if society did not break down (a big if) I don't think agricultural production itself would be an insurmountable hurdle. I suppose I am more optimistic than you about the problem-solving and organizational ability of people put in this situation. $\endgroup$ – user16107 Jan 29 '16 at 11:02
  • $\begingroup$ @Burki if you want to look for real world examples, there are plenty of cases where major infrastructure has been returned to being operational astonishingly quickly after devastation in war. Don't underestimate human capacity when it is life-or-death and all red tape has been cut through, etc. $\endgroup$ – user16107 Jan 29 '16 at 11:07

If people and governments understand what is going on, and that it is now safe to go out again, the food problem could be solved. Sure, there would be widespread economic disruption and a drop in the standards of living, but it will be the confusion that kills the survivors.

  • There will be enough underemployed people in the urban areas to become a sufficient farm workforce for the (now reduced) population.
  • There will be enough former and current farmers in those urban areas to serve as teachers and foremen.
  • Saving the animals will be a question of days or hours. A modern dairy cow won't survive long without human care. There is enough livestock within one day of travel to serve as breeding stock. Perhaps the meat consumption will go down for a time, but that is healthy anyway.
  • Saving the crops will be a question of weeks or months. You said the hardware survived. So what if the new driver for a combine harvester runs over half the crops, there are enough planted fields.

The impossibility will be understanding and organizing. Will the urban people believe that it is now safe (and urgent) to go out? Can farmers and helpers be dispatched to the big commercial farms before the animals die?

Similar considerations will apply to energy (rush people to the nuclear power plants, get enough people to the coal mines to keep the pumps going and restore operation later), transportation (save river barges and ships currently in port for future use), communications (maintain undersea cables).


They will all die.

Well. Not all of them. But almost.
While farming is not rocket science, it still takes some skill, and more than you can learn from books in a few weeks.

So, while those that are quicker on the uptake will try to save what farms they can get hold of, a large part of the population will kill each other trying to claim what food and other resources can be found in supermarkets.

In the mean time, cows need to be milked, chicken need to be fed, and so on. With noone caring for the livestock, a lot of the farm animals will die pretty quickly.

So, a lot depends on wether the first harvest will be lost completely, or if part of it can be brought in.

Practically every bit of infrastructure will collapse quite fast. For example: A lot of the big power plants are not in city centers, so their personnel will be hit by the weapon. Can you train new personnel fast enough to prevent neglect rendering them useless, or even dangerous?

The big refineries will share that same fate.

So, to round it up: Those people who don't die in the anarchy and looting will have to re-establish agriculture and what infrastructure can be saved, losing large parts of what we are accustomed to, like fuel for cars(described above), health care (you need medicine, requiring processing of raw materials), energy and heating (described above), food distribution.

The cities will quickly turn into mostly empty heaps of rotting corpses, while a very small part of the original population will live off whatever agriculture they could grasp quickly, without the help of diesel engines and mostly without electricity.

Not a bright future at all.


The biggest hazard here is actually fear, fear of whatever wiped out people the first time around. Who is going to leave the safe and shielded city to go out to the farms and provide food? Can people prove to them that it won't happen again?

There's a lot of infrastructure outside of cities. Power generation, factories, waste water treatment, to name just a few. Even if your generators are still working and still inside the city you need fuel for them. Your water supply almost certainly gets piped in from outside.

You can expect martial law, poverty, riots and hardship. I would expect the majority of people to survive, but it will be a lot fewer than the original 20% of the worlds population that survived the initial catastrophe.



As seen on this graph of the world population in 2015, around 20% of the total world population lives in city's lager than 2 million people. That comes down to 7.398.158.900 * 0.2 = 1479631780 people. Considering this and the fact that most ( if not all ) world leaders also live in these city's i'm quite sure they will do just fine.

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    $\begingroup$ Provided none of them needs to eat, or drink fresh water, or have electicity or heating. $\endgroup$ – Burki Jan 29 '16 at 10:30
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    $\begingroup$ "most ( if not all ) world leaders live in these cities". Not quite. At least 75% or so of the world's capitals are cities below 2,000,000. While the largest countries tend to have large capital cities, significant chunks of the world including the U.S. and most of Eastern Europe, would be without an effective government. And even where the capital city survives, how well would government function when all local administration and services disappear? $\endgroup$ – user16107 Jan 29 '16 at 10:45
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    $\begingroup$ The countrys where the capital has less then 2 mil people would be renderd usseles as it's quite common for the capital to be the largerst ( or one of the lagerst ) city's in the country. While both of you make a persuasive argument i'm sure the people will not only survive but thrive after some while. And while lifestock my die out and the current genartion of crops also farms wouldn't be useless after that and while most of the famers would die out because of the superweapon there are enough people in the city's that study agriculture. $\endgroup$ – T Jasinski Jan 29 '16 at 10:56
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    $\begingroup$ And the fact that most of the social services disapear ( power, heat, and so on ) might be the biggest problem but people live every day with far less than what most people will be left with after the super weapon $\endgroup$ – T Jasinski Jan 29 '16 at 10:59
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    $\begingroup$ @TJasinski supporting information needs to go in your answer, not comments. $\endgroup$ – user16107 Jan 29 '16 at 12:05

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