We already do this with a society, no AI required.
Having people live longer means more people means we need more food and water of which there is a finite amount. There is only so much arable land, and so much water that can be made potable. Removing the salt from the oceans is quite expensive, and adding more waste to the existing fresh water would make it more expensive to make potable. Not to mention places to live near where people can work.
These are all hard problems to solve. There's no magical AI to solve it for us.
