Depredate derives primarily from the Latin verb praedari, meaning "to plunder," an ancestor to our words predator and prey. Dating to the 17th century, the word most commonly appears in contexts relating to nature and ecology, where it is often used to describe the methodical, almost automatic destruction of life. That's how the film critic Stanley Kauffman, for example, used it to summarize the plot of the famous horror movie Jaws (1975): "A killer shark depredates the beach of an island summer resort. Several people are killed. Finally, the shark is killed. That's the story."
Word History
Etymology
Late Latin depraedatus, past participle of depraedari, from Latin de- + praedari to plunder — more at prey entry 2