A wasteland or scorched earch etc shouldn't kill an army that wanders into it, while "repairing it" takes resources, I agree, but that would be a conscience decision, and more akin to the blockade card (I think a better name for blockade, in fact)
After re-reading what you wrote here and reconsidering, I do think you might have a good point about how Blockade could/should be renamed also, perhaps to Scorched Earth.
So, perhaps:
Abandon -> Trap or Entrap (or Minefield, or Undermine, or Sabotage, or something similar)
Blockade -> Scorched Earth (or Waste/Lay Waste, or Ruin, or Raze, or similar, perhaps even to Abandon).
Though I'm not totally sure of this, because, historically, scorched earth policies have been used often in the face of superior advancing armies to slow them down/disable them, so it still fits with the mechanics of the current Abandon card. On the other hand, your point about whether to pursue/clean-up being a conscious decision is a good one, IMO. That's why I suggest Trap/Entrap, since that emphasizes that the costs are not consciously chosen, but 'sprung' upon the pursuer. Only problem with trap/entrap is that the 'trap' doesn't lay in wait like most traps; they either blunder into it immediately, or the 'trap' is immediately revealed and it is no longer a 'trap', but merely an obstacle. Again, I'm reminded of 'obstruct' as being a pretty good word for one of the two cards.
Edited 9/11/2015 02:46:24