Originally posted by Soondead:

Even knowing I want to reach a swamp before plains, the simple problem is that I have yet to find one next to a black forest. There's always atleast a thin strip of plains nearby with those damned deathsquitos completely ruining any attempts at getting to the swamp. I end up getting one-shot killed, running back zig-zagging between skeletons and greydwarves while wearing reserve armor to get my stuff back, skills plummet until I can barely hold a bow and my food reserves are exhausted. I really, really hate them and I'm pretty sure I'll quit playing again because of them.

Your closest swamp is always closer than the closest plains, this is just how world gen works. If you're finding plains before swamp, you're traveling too far from center.