I've implemented population growth/dying processing. How it works is this: It calculates the normal population growth, factoring in remaining space, and current population. It then calculates any extra population growth from food surplus, or negative growth if food supply is lower than population count. It adds both (note, the population growth from food is higher on per-unit basis than normal growth, so starvation can easily outpace population growth), then add the total to population. If population drops below 0.1, the planet has died off and you lose control on the planet.
Now for pollution. If it's above the cleanup efforts, the planet's population capacity (i.e. max population of 100) will drop. You can fix this by increasing the cleanup so it exceeds the pollution. This slider will also act as terraforming when you get appropriate technologies. Pollution don't affect the planet's capacity right now however.
After some deliberating, I've decided to remove the infrastructure part of the planet. All output will be direct from population. So the more people you have, the better. This is similar to Master of Orion 2 where you allocate people to different fields. But there won't be any special buildings to build that enhances your output. There will be technologies that automatically increase your output however. This will make things simpler and less confusing, both on user's end and developer's end.
There's three more items that I would like to see completed before I release the next version. Those are:
Influence maps for computing which planets to migrate to
Migration code (calculating how much people migrate from a planet, and how much will arrive at a planet)
Ship construction UI/code
When the three items are done, then we'll be back at where I started refactoring. The old version had construction and colonization. Then I'll start focusing on research and ship designs :D