The case of the shrinking town: AI cities losing population

Hi guys, I'm new here but have lurked for a long time. Thought I would finally jump in.

One thing I've noticed in several of my BNW games (and never before) is a situation where an AI town has shrunk in population and in one case disappeared completely. I have searched for explanations a couple times, but turning up none I came here.

The cities in question were all revealed but were covered in the fog of time. Meaning the tiles were not always up-to-date, but AFAIK the population numbers were updated as the town grew. That said, things I have observed:

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  *On three separate occasions I've seen an AI capital dwindle down to comically low population. The most severe case was Berlin shrinking down from twelve to two citizens before finally creeping back up to 10 people by the end of a long game. It was on the all-jungle map. His second and third towns were fine, though (20+ citizens). I have also seen Moscow shrink down to 5 citizens before rebounding and Carthage cut to half size. In all cases there was no war going on with the capital that I was aware of.
  *Similarly, I have seen other AI towns slowly begin to shrink in population. Today I saw Borsippa (Babylon) shrink from 6 population down to 1. Geneva, a city state, also shrunk from 7 to 5 people. I know this because I was winning at the religion there (I had 4 followers) but when it dwindled to five I was no longer majority (it was contested and I had only 2 left, not enough to dominate).
  *Today I saw a new extreme. A puppeted AI city with 2 citizens shrank to 1 citizen and then eventually disappeared. No city ruins were left. It was just gone.

I could produce a savegame for those last two events because they happened in the game I played today (sandstorm map). I am not using any mods, just BNW+DLC. I'm not really sure how to capture what's happening in a savegame since it's so gradual, though.

What is going on? Is it a bug? Are they starving the town to death? And has anyone else seen this happen?

May be other civs razing captured cities.

There is a very conspicuous icon when a city is being razed, and none of the cities had that.

Also, I should have mentioned this dwindling did not take place over directly successive turns. It took a while for them to shrink (several ages for Berlin).

Really the only thing I can think of was the AI was starving its own citizens, prioritizing production over growth. In fact, I remember in that Carthage example she was cranking out wonders - causing me to lolwut when I saw she had 7 citizens (I had around 18 at the time).

The AI is (very) bad at choosing which tiles to work. It's possible that it overworks tiles that have less than 2 food, which would lead to starvation. Still it's bizarre that they'd just let that happen.

My best guess is that it Berlin was being pumped up by intercity food trade routes. When they switched those to something else, they'd collapse population wise (it's happened to me before, but never more than -1 pop). And as for disappearing completely, it's either city-razing or a glitch. Perhaps one civ sold a city to another, which then raised it, no war involved? Seems weird but it's the best I can think of.

All I can say is you're pretty darn observant to notice some of this stuff in the first place, and if you want real insight in to what's going on, post a spy in the city to see the food yields and such. I'd be interested to find out!

However, the AI uses the same routines to prioritise that it does for your cities and for puppets - I don't notice my puppets getting smaller, and its default focus is food (to the point that when you try to assign food-producing citizens to other tiles of your choosing, it will redirect a citizen from a production or gold tile to the one you just vacated). So it's not clear why it would behave differently with its cities.

The obvious possibility is that the city was nuked, but this should be evident from the surrounding landscape.

I frequently play on hostile terrain maps like sandstorm, the tundra map, the jungle map, etc. Since food can be a big deal on those I often track my progress comparing my city sizes to theirs. They mostly fail at feeding themselves. On that sandstorm map I just played, when the food report came some people were making .2 food (yikes). And you know how city states are, they can be in the darndest places (Geneva definitely did not have much food).

Maybe it happens when most of the food is de-coupled from everything else, so a shift in strategy (to production, for example) completely yanks the rug out from under them.

I'll keep watching during my next game and report back if I learn anything. Good point on the spies, too. I don't usually notice the drop until it's extreme, but maybe if I'm lucky the condition will still be there when I re-assign my spy. In fact, I'll go and load that game and see if I can see anything in Borsippa or Geneva.

Alright, reporting back. I can't look inside a city state (duh, forgot that) but I could study Borsippa. I also was able to draw some conclusions about Geneva.

TLDR; it's legit. I think this happens when a city is on a fragile food economy, grows way bigger than it should have, and then its house of cards collapses.

Case 1: Borsippa. As we can see below, it's in a crap spot. I couldn't look back farther than this, but I know it had 6 people at its high. Maybe it was being shipped food. Either way, it had to be eating the fish to grow (has no food otherwise) and I bet barbarians from the nearby snow blockaded them. Everybody starved.



I also Babylon was being revolutionary waved by my culture, and was very unhappy. Hence they decided it was best to crank out a zoo, despite the fact they shrank to a single citizen and the timeline grew longer. Irony: zoos need people for happines.

Case 2: Geneva. Though not as bad off as Borsippa, Geneva has few options for getting food and other yields simultaneously. I suspect at its max of 7 people it decided to focus on other yields instead of food (for example that silver node). I don't remember any barbs happening to it (no "under attack" messages) but I wasn't watching it that closely until I noticed my religion wasn't dominant anymore. Perhaps the sheep got razed briefly, for example.



I don't have a savegame for Berlin or Carthage, but based on these examples I suspect I'd see a collapsed food network plus a bad production decision making it worse.

Thanks for the nudge so I could figure this out, guys. I'll update if i see another interesting case. Keep your eyes out, okay?

So it's happiness management, basically - the AI gets unhappy (not a situation it needed to be programmed to deal with pre-BNW...) and doesn't know how to shift its focus to avoid starvation; have you seen this happen in pre-ideology eras, or with happy AI civs?

By the way, what is it with the icons turned on (oil, wheat etc.) I see in so many of these screenshots? It makes reading the game situation very difficult, especially in city view when you just want to see yields at a glance.

PhilBowles said:

have you seen this happen in pre-ideology eras, or with happy AI civs?

Click to expand...

Both the Germany and Carthage examples were pre-ideology (save games long gone, sadly). I recall Germany was in solid jungle (well, everyone was on that map) with a lot of open jungle outside their border. Barbarians probably caused their food supply to collapse while they focused on producing something and starved, slowly stretching out their timeline and locking them in a vicious cycle.

Carthage was coastal and in mostly in bare hills. They were getting almost all their food from the water and when they decided to wonder rush I think their production focus starved them. They did finish several wonders (lighthouse, colossus, oracle, I think there was another) before starting to grow again.

So, I think those were situations where an AI was hell bent on a certain structure and wouldn't adjust course due to starvation.