What are the motifs in Pilgrim at Tinker Creek by Annie Dillard?

Throughout the book Dillard is marveled by all of the life and also all of the death she sees every day. Constantly she is wondering about a God, or creator, that would feel the need to create such destruction when so much of the world is alive. But she comes to the conclusion animals die because they have to, it is simply the way that it is.