The Simulation Game

The title is a pun because there is a movie with a similar name. Hurr. Anyway, Cultura, when it's good and ready to be released will involve farming. The end game will be the neolithic time period so the hope is that you'll be fascinating with min/maxing your empire, engaging in endless diplomatic schemes and building wonders. Also trading with distant lands and marching armies. But back to farming, the lithic time period of humans is probably split between pastoral societies and agrarian societies. There's some mixture but what's important here is getting down to the basics.

This is a simulation game of building up a society from the ground up and so the best place to gather numbers for game mechanics is the real world. Cultura is a game where it doesn't tell you what works, what doesn't and what policies get you what bonuses, instead you do what you want and then the simulation takes care of the effects in a natural manner. With farming, it means that the land production values are going to be design something along the lines of real life.

Okay, let's look at agrarian production rates:

• 223 kg/ha in Han Dynasty based on a statement from an official commenting on unfairly high tax rates
• 442 kg/ha in Qin Dynasty based on a statement from an official commenting on new farming methods
• 1431 kg/ha in Egypt Middle Kingdom based on a priests's statement on what a "good harvest" would be
• 714 kg/ha to 1429 kg/ha in Egypt New Kingdom based on some records from archaeologists

So that varies a lot and the Nile is especially productive. That's not a surprise; China's Yangtze is not going to be good competition against the floodplains of the Nile. We could probably average the Egyptians to be around 1000 kg/ha. The Chinese number is harder to judge but perhaps we could just take an average and say it is 300 kg/ha.

That brings us to pastoral societies. What kind of food production might one expect from herders? And for that matter, animal meat production.

• 1.16 kg/ha meat + ?? kg/ha milk for the Borana

That data... is a little sparse but there's little data gathering for pastoral societies. For the Borana, there's around 1162 kg/ha dry mass produced from the land they live on, on average per family, including the wet/dry areas they might move about in. They mostly rely on milk products to survive and their population density is exceptionally low. Each person lives on around 43 kg of meat per year plus a lot of dairy.

Lastly, we want to look at what animal production would be for grain-fed farm animals. This is important for mixed farming (where you do both herding and growing crops). These numbers come from a Stanford study:

• Cattle: 8:1 feed to mass ratio, 20:1 feed to edible mass ratio
• Pork: 7.3:1 feed to mass ratio, 4:1 feed to edible mass ratio
• Chicken: 4.5:1 feed to mass ratio, 2.5:1 feed to edible mass ratio
• Milk: 1.1:1 feed to mass ratio, 1:1 feed to edible mass ratio
• Fish: 3:1 feed to mass ratio, 1.8:1 feed to edible mass ratio

These are fairly rough numbers and what they translate into game design here is relative values. So we want good arable land to produce around 200-400 units of food per square area, we want dryland to produce around 1100 units of dry mass for fodder per unit area, and we want a conversion ratio of grain feed or wild forage in the table above. Dryland would be unsuitable for growing crops, while floodplains would be super productive at 700-1400 units of food per unit area. We could translate this to being something simple like: dryland produces 1100 dry fodder per square per year or 50 units of cereal (so not worth it), grassland produces 450 units of cereal per year (or perhaps 1500 dry fodder?), floodplains or other super area produces 1000 units of cereal per year (and perhaps 2000 fodder?). Looking at data for dryland crops however appears to show that they can have quite good yields and especially during ancient times they may have rivalled the twentieth century yields (though I suspect that it was unsustainable and led to destruction of soil fertility since they would not have had access to many other technologies that could have kept up soil fertility).

I think perhaps I may simplify soil fertility or I may not, it depends on the sort of decisions it can give the player. If I bring in the concept of soil fertility, the idea is that certain technologies can maintain the fertility levels (such as the application of manure) but ultimately the land plus the technology determines the carrying capacity and going beyond this is a short term gain at a long term cost.

Soil fertility might be some value which decreases per unit harvested off of the land, increased by technological tools (such as manure) up to the max of what that technology can provide and there is some natural regrowth (and maximum). That model gives a very simple way of expressing responsible land use to the player, something well studied throughout history (accidental over farming leading to exhausted soil and then agricultural collapse) yet is still very very lenient because it doesn't consider fertilizer run-off causing algae blooms, deforestation leading to changes in the water cycle, drainage of wetlands leading to flooding and so on. I'm not quite building a weather simulator here but how far should I go to create the simulation to avoid sacrificing emergent properties that come out of environmental questions of how a society interacts with the land it lives on?

Deforestation can already be pretty devastating in the game. Wood is obviously a very useful resource but the growth rate depends on the number of trees. Chopping more trees gets you more wood but decreases the forest growth rate. It's similar to grasses and whatnot. Luckily, the player does not need to think about canopy cover and the like that prevents the soil from drying up from being overly exposed to sunlight. So your overgrazing won't lead to desertification but it does lead to loss of grasses and then your animals die of starvation, then you die of starvation.