Calories Per Acre
Note this is a per-year number.
On the consumption-side, people need ~2500 cal/day, which is 912kcal/yr (or roughly 1M).
- grains 6-18 Mcal/acre (potatoes/corn much better than wheat)
- meats 1-3
- Grass-Fed beef is actually lower, I think, but can use land that isn't good for growing staple crops anyway.
- apples 12-23M! (latter is commercial production)
- romain lettuce 1.3
- sweet potato 8.5
- apples 8.5
- cherries 2.4
- see section on insects!
almonds 5.4k? (2k lbs/acre, 170 cal/oz)
So taking a crude fake avg of 8M/acre, I conclude that each acre can support 8 people, or a sqmi can support 5k people. (Population Density)