Biome ids that are never settled where they dominate (weight > 0.5) and thin out settlement elsewhere.
Fertility of biomes missing from fertility.
Fertility 0…1 per biome id (blended by biome weight).
Slope (rise/run) at which land becomes uninhabitable; gentler is better.
Most comfortable temperature, °C.
Temperature distance (°C) at which comfort drops to 1/e.
0…1: how much fresh water (rivers, valleys) or a coast nearby matters.
How good a place is to live: each factor is 0…1 and they multiply.