What conditions are required for civilization to exist on this planet while the sun provides a suitable environment?
Predicting the future is rather difficult. But we may find information from the assumption that civilization(s) continue for millions of generations. Let us not (here) think about how (or if) we believe this can or should be reached.
(Please consider work that has already been done to avoid repetition.)
If a civilization continues for million of generations...
What would its average rate of population growth be?
What mechanisms could keep the population from falling below critical limits?
What mechanisms could keep the population from rising above critical limits?
What threats would it have to survive? How could it do it?
How much would its average economic growth be?
Could it keep on increasing its knowledge? How?
How could it retain knowledge?
Where would such a civilization get its energy from?
What resources would it need? Where would they from?
How much of the vital resources can each generation consume?
What does sustainable mean?
What would influence the number of individuals alive at any one time?
Which threats may exist that are beyond its control?