Patch ArcanaThis is your reminder that any geoengineering technology with the potential to terraform a world could also be used to restore the equilibrium of this one.
That's not to say you should never terraforming things I'm just a big fan of "put the fires out before you start building the new cabin" as a general rule of work ordering.
ARGVMI~1.PIFUnless it's the Genesis Device from Star Trek, which destroys the target planet and replaces it with a new one.
The new one is quite hospitable for humans, but if it were used on Earth, no humans would survive to enjoy that hospitality.