The interesting thing is that although it is called the Dark Lands, the areas of highest CD made pollution would be immediately around the major cities. The natural pollution from volcanic gasses would probably be much more widespread than anything the CD could do.
So I would limit the plant and animal life immediately around the major cities/ volcanic areas to survival of the fittest.
Beyond these areas there might be big forests that are maintained for logging clans, subsidiaries of the river ruin, small lakes etc. All of these could have relatively normal ecosystems imo. The marsh/ swamp areas are normally high in animal life. I don’t picture the whole darklands as a desert, even areas that have acid rain recover a little every now and then. If you translated the warhammer world into the real world, the dark lands would be what, about the size of USA? Even some major cities like London would not really dent the environment as a whole overall, so it’s all down to the natural pollution.
Well, if it's part of an army list for an army that comes from that area, we might imagine those creatures are native to that area.
Like how horses live in Bretonnia and Dragons live in Ulthuan. Make sense?
It makes perfect sense, but nowhere in the original post is there a request for, or a requirement for, suggestions to be part of an army list. Wolves are no more virtuous as a suggestion simply because they could be used in an army list...