RPGMemes

Yeah, things that, so long as they don't teleport somewhere for literally no god damn reason, will only change in response to something they do. If you plan for there to be a bandit camp in the, but they avoid it and set fire to the forest somehow, now forest bandits flee into the plains and set up camp again, interact with something there, or disband.

Encounters, easy. You were going to prepare those anyway.
Maps, not as easy but there's resources online in a pinch.
Forces... What do you mean by that?
Terrain... That's just maps again, right?
Ecosystem... Yeah, you're definitely over-preparing at this point.
Descriptions... You shouldn't have been prepping this anyway. If you know what the thing looks like, you can describe it yourself during the game.

:laughs in random table generation:

I haven't actually prepped a session in ages. I learned The Keep on the Borderlands well enough, and use the encounter generation rules from the Rules Cyclopedia for everything else.

I procedurally generate everything while we play. Which makes it a game for me, too - I get to interpret the results of the rolls in whatever way seems most appropriate and fun at the moment. And, in the end, it doesn't really slow anything down compared to 'normal' DMing, where I'd often have to cross-check notes, the adventure, etc to determine how the PC's actions play out.