I started this post back in April based on the evidence of there were no more magic beans, and that the enchanted tree used for the wardrobe was the last remaining tree. In addition, others have speculated that dragons and pixie dust were in limited supply.
Finally we have another example from season two, episode three: magical Lake Nostros has evaporated, or has the water been taken by someone or something? I don’t believe the death of the Lady of the Lake caused the water to vanish. It seemed important for the writers to set up Snow and PC’s mother needing the water from the lake so the writers could show us that the lake was now gone. Why explain it off as it vanishing from PC killing the Lady?