how does the change in setting influence the mood in 'a fable for tomorrow'?

Carson sets the scene for the entire book with this "once upon a time" introduction. The description of the pre-destruction town and countryside is idyllic, full of lush detail about specific flora and fauna. The language is fairly rhapsodic in its celebration of the harmony between man and nature that once existed. She continues the fairy tale tone by describing the mysterious blight as an "evil spell" falling upon the land and its creatures, including human beings. Again, she uses specific detail to create a vivid picture in her readers' minds: the birds tremble violently before they die; where there had been throbbing birdsong, now there is silence; chickens and pigs stop producing young; the roadsides look scorched as if by fire. Finally, she snaps the reader out of the fairy tale by stating that the people themselves have caused the widespread destruction of life. In the final two paragraphs of the chapter, set apart from the "fairy tale" by a space, Carson explains that the town does not actually exist, but that the individual examples of environmental destruction have indeed taken place in various locations. She does not yet identify the "grim specter" that has caused so much death, but says that in this book she attempts to explain why spring is now silent in so many American towns.