The Invasive Species Specialist Group (ISSG) aims to reduce threats to natural ecosystems and the native species they contain by increasing awareness of invasive alien species and of ways to prevent, control, or eradicate them. The ISSG facilitates the exchange of invasive species information across the globe and ensures the linkage between knowledge, practice, and policy so that decision making is informed. To support these efforts, ISSG has compiled a list of “100 of the World’s Worst Invasive Alien Species.” View photos and learn more about these species’ habitats, impacts, uses, and the geographical range.