Space Exploration - Vitamelange planets and trimming surfaces

[iAndy]

When I clear all the biters on my vitamelange planets, it only reduces the threat to 1%. Does this mean if I trim the surface, they can respawn in the deleted areas? I have 10+ meteor defense installations on each one so no meteors are going to land but I'd like to keep my save file size a bit smaller.

[RiO]

Yes; it means they re-spawn in deleted chunks as soon as those become active again.
Which is not necessarily when they are revealed; but is actually when anything in the game interacts with those chunks again, incl. - which is primarily relevant for biters - the pollution cloud of your factory.

This is one of those cases where the mod's author didn't quite think things through when they deployed their counter-measure (biter meteors) to 'balance' the game (read: force you to play it the way they wanted you to play it).

There are more cases of this kind of annoyance seeping in.
It's the reason I quit my earlier playthroughs of SE, actually.