Could make an encounter where the player confronts an enraged Pokemon in either places. Might even be able to fit into your storyline maybe, depending on what you could be going for. If there's a lake inside one of the forests you could have a little island in the center with a tomb on it, giving directions to something like a treasure or something. This one is on-going and once the last clue has been found, the player is directed to a spot in the game where they find like a hidden area just filled with Pokemon that could be from all over. In order to enter this hidden area have certain items be found at some points in the game where the clue's/directions are located.
A little girl could wander off into the forest one day, and their parent(s) make a big fuss for help. Makes more sense in a rural town where there aren't usually police of some sort - So that the player can get a reason to help out. Everyone else is too busy working? Or they're just all afraid of something within the forest to help out? Your choice.