Population Capacity
A new concept, Population Capacity, has been added to C# Aurora. This represents the maximum population that can be maintained on a single body and is primarily determined by surface area. This is the total of all populations on the same body, not per population.
The Earth's population is currently seven billion. However, the rate of population growth peaked at 2.1% at four billion, has been dropping since then (now 1.2%) and is projected to reach close to zero around eleven billion
https://ourworldindata.org/world-population-growth/Therefore, I am going to use twelve billion as the baseline max capacity for an Earth-sized planet and four billion as the point at which growth rates are affected.Growth will follow the normal rules for up to 1/3rd of max capacity and then will fall off at a linear rate, hitting zero growth at max capacity (replicating the situation on Earth). The max capacity of a body will be equal to: (Surface Area / Earth Surface Area) * twelve billion. I will add some tech options to improve that capacity, particularly for smaller bodies. A planet can physically hold more people than the max capacity but this will result in unrest due to overcrowding.
While 70% of the Earth's surface is water, that plentiful water also improves living conditions (the majority of the world's population is less than 100 km from the nearest coastline). However, there does come a point when too much water will reduce the available living space. Therefore, once water covers more than 75% of the planet, capacity will drop at a linear rate, falling to 1% of normal capacity at 100% water. The 1% assumes a few, small, scattered islands or some form of colony floating on the surface.
Tide-locked worlds (one side always facing the star) have only 20% of normal capacity (after taking into account surface area and water). This is to simulate that the population will be living in a narrow band between the light and dark hemispheres of the planet. To compensate, these worlds also have an 80% reduction in the colony cost factor for temperature (as they are living in the temperate band).
Regardless of the result of the above calculations, a body with gravity at or below the species maximum that is not a gas giant or super-Jovian will always have a capacity of at least 50,000.
The above rules result in the following population capacities
