This work investigates the critical decline of various North American animal species and the environmental factors contributing to their potential extinction. The authors, Joseph Anthony Davis and photographer Nina Leen, utilize a combination of visual documentation and biological observation to highlight the precarious status of species such as the Florida manatee, the puma, and the bald eagle. The text serves as an early environmental assessment, framing the loss of biodiversity as a direct consequence of human encroachment and habitat destruction.

Experts recognize this work as a significant visual record of mid-20th-century conservation concerns. Readers frequently note the effectiveness of the photography in humanizing the plight of endangered animals for a general audience.