Star Trek Discovery: Every Easter Egg & Hidden Reference From 'That Hope Is You'
2. Endangered Species
Late in the episode it's revealed that Book isn't just a smuggler, he's actually a transcended human who can commune with plants and animals.
As Michael states plainly, without the Federation in the 32nd century, there's no one to enforce the Endangered Species Act, therefore Book has taken it upon himself to save endangered animals (including the weird "trance worm") and return them to a sanctuary planet.
The Endangered Species Act was previously discussed in the Discovery season one episode "Magic to Make the Sanest Man Go Mad". In that episode, the act applied to the gormagander space whale which was illegally "penetrated" by Harcourt Fendton Mudd (see also: Short Treks "The Escape Artist").