It's part of it. Caribou are a very complex species, but where you are talking about, up on the Alaska coast, the Porcupine herd is in full recovery. The numbers are on the increase. The Carmacks herd in the Yukon that was almost hunted into extinction in the gold rush a hundred years ago has made a great recovery.
I don't think it's doom and gloom for caribou. I think they will recover. As to how much of it is related to climate change and how much of it is a natural cycle, I don't know.