Nature, or natural images, (I will take this to mean nature images, which is how the novelist uses the five senses to describe nature--- a novel is a work of art and art, by definition, is not "natural," and thus, it does not use "natural" images) help set the tone...
Nature, or natural images, (I will take this to mean nature images, which is how the novelist uses the five senses to describe nature--- a novel is a work of art and art, by definition, is not "natural," and thus, it does not use "natural" images) help set the tone or mood of a story. For example, the opening line of A Wrinkle in Time, about it being a dark and stormy night, parodies a stereotypical opening line in a bad novel, but also points to the importance of setting and establishing a dark tone for a story that will be as much about combating evil, as about the importance of love and family.
Wuthering Heights is an apt example of a novel in which nature and love of nature play an outsized role. Catherine and Heathcliff find their bliss running wild on the moors, and Catherine especially is associated with the wild, craggy moorland, telling of a dream in which she sobs for joy when, after death, she is thrown out of heaven and returns to her beloved landscape. In this case, the nature setting becomes identified with these two figures, who stand outside of the norms of civilization in their deep, unconventional love for one another that transcends death. In contrast, a novelist like Jane Austen satirizes an excessive, romantic love of nature in a novel like Sense and Sensibility by ridiculing Marianne (who represents sensibility or emotionalism) and her excessive love of nature and nature poetry, showing it to be dangerous and even life-threatening as Marianne's fantasies about Willoughby make her very sick after she is confronted with the reality that he will not marry her.
In sum, how a novelist uses nature imagery--how a novelist manipulates the five senses to control how we experience nature in a story--sets a tone, be it of foreboding, joy, gloom or mockery--that contributes to how we understand the novel.