Here’s an interesting post by James Davis Nicoll: More Planets, More Problems: The Pessimist’s Guide to Galactic Expansion
This is pessimism based on statistics:
[The statistical unlikelihood of being hit by a giant meteor is g]ood news for any particular world, because the odds are pretty good that civilization will collapse from other causes in the time between successive 1 km object impacts, with excellent odds that the species will vanish from other causes before another dinosaur-killer arrives. Unfortunately, our grand galactic polity has three hundred million independent planetary collision experiments running simultaneously. Thus, absent intervention, in any given year, about six hundred worlds will be struck by a 1 km object, and about fifteen will be struck by a massive dinosaur-killer.
That paragraph made me laugh for a couple of different reasons. Good news! Your civilization will fall and your species will become extinct before you have to worry about being destroyed by a giant meteor — well, MOST of you.
Of course, in a properly run galactic federation, we wouldn’t say “absent intervention.” We’d expect nearly all of those worlds to nudge the giant meteor out of the way before disaster struck. Except that Nicoll is in a REALLY pessimistic mood this morning, as he adds, Well, unless the funding bodies decide that because there have been no impacts in recent memory thanks to the anti-impactor program, the program was clearly overfunded and could be cut.
Nicoll then goes on to discuss other planetary catastrophes, including my favorite, the kind of extreme volcanic period that formed — for Earth — the Siberian basalts and would — if it happened again — kill us all. Nicoll comments, with the extreme pessimism that pervades this particular post, I guess the good news is “an area the size of India is permanently on fire” is the sort of thing people notice from orbit, so at least it won’t come as a surprise to whoever makes the mistake of settling there. Unless, of course, the flood-basalt event is in a quiescent phase during the survey…
These sorts of things are not as fun in space opera as a good old-fashioned war, but I suppose if you’re writing a long series and the war doesn’t seem exciting enough, you could probably spice it up by adding a nice planetary catastrophe on top.