How does the author address environmental issues in the novel, The Night the Heads Came?

The social commentary in The Night the Heads Came is incidental, and the environmental issues are introduced at the end by way of explanation for preceding events and to explain the importance of Tim's pictures. There is nothing extraordinary about acknowledging the harm humans have done to Earth; the narrator Leo notes that humanity is ruining its environment and that without significant changes in how it handles its resources, humanity could render itself extinct, leaving a near-lifeless and ruined planet to the Others.