Thank you guys, I checked it and it was on, and the command successfully turned it off. I'm not really going for achievements, so I just left them off.

I just loaded up a world I had made a couple days ago, and really got into it. I can't remember if Biter expansion is on or off. Is there a way to check that, and if it's on, to turn it off? (Lua commands, file editing, the like)