There's a bug on the mountain stage where the game wants you to make wetland. There is not supposed to be any wetland on the mountain stage. Sorry about that, the only fix I've found so far is to restart the map :(
Ah, okay. Hopefully that'll get ironed out in a future update (I know it's still in development). Am enjoying the game a lot, so can live with re-starting the map. :)
Playing it again, it seems that when you quit to the menu then continue the saved game, it changes from three biomes to four, so the issue seems to be with loading saved games.
