Bozeman, Montana
A subtle use of imagery tells the reader what Roy has lost by moving. It isn't just the mountains of the Montana horizon, but also what they represented to him subconsciously. By moving to flatlands, he no longer sees the mountains containing his world. He is not cozy or contained. He can't look into the distance and know what lies out there in the distance. This makes Montana a comfort zone for him, and when he moves, the mountains are an obvious sign for nostalgia.
Coconut Cove
Let's just say Florida is not really Roy's cup of tea, at least not at first. He doesn't appreciate the climate change (Florida is very humid compared to Montana, and also very hot), and he loses several things in the move. He loses seasons of the year, because it doesn't snow in Florida, nor does the fall bring the same climate changes he is used to. More importantly, he feels the land is horribly flat, and the lack of topography makes him depressed, because he never noticed how much he loved the mountains of Montana.
Naturalistic imagery
When Roy sees Mullet Fingers (notice that both Mullet's names refer to the body), he encounters an avatar of the Florida wilderness. This boy doesn't wear shoes, and whereas Roy sees the world in terms of his own prospects, Mullet sees the world an entirely different way. He sees the lives of the animals who live in the Florida flatlands, like the owls who depend on them for salvation. Roy would never have noticed if the owls went missing, and that's a thematic problem in the book.
Social construction
There are social constructs that shape Roy's experience of his environment. For instance, he comes into direct conflict with his community when the move makes him depressed. People don't like to feel like they're depressing to look at, one might say, but more importantly, Roy becomes a target for bullying. Then, later, he has to confront the society for its negligent use of social constructs. He builds a new construct with his friends, convincing people one at a time to fight for nature and for owl protection.