The Earth is dying. As the novel progresses the slowing the Earth becomes more pronounced. This is in direct parallel to the slowing or the end of Sylvia's childhood and a loss of childhood's innocence. The simple act of writing 'We were here' in the concrete reinforces the themes of coming of age, as well as that of hope in the odds of great adversity. She does know that even after she is gone, their names, the date and the words "we were here" will still be written in the concrete outside her house.