Popular and accessible before television and the internet, picture books capture the context of the time they were created and influence the generations of children who consume them. Depictions of the natural world have changed across several generations of picture books as seen in illustrations of all 249 books of an influential collection, the Children's Book Council of Australia Picture Book of the Year Awards shortlists from 1955 to 2014. This study found that natural environments became proportionally less present in picture books over time while depictions of built environments increased. The presence of wild animals and native Australian animals also decreased over time. Sustainability themes and more realistic depictions of wild animals and biodiversity increased over time which reflects a growing ecological or environmental awareness, and diversification of environmental themes in recent picture books of this prominent Collection.