100 of the World's Worst Invasive Alien Species

[1][2] The database is run by the Invasive Species Specialist Group (ISSG) of the International Union for Conservation of Nature (IUCN).

The ISSG acknowledges that it is "very difficult to identify 100 invasive species from around the world that really are 'worse' than any others.

Absence from the list does not imply that a species poses a lesser threat.

"[1] In 2013, the ISSG updated their list to supersede the recently eradicated † rinderpest virus, and a few genus and species names were altered.

This list has been updated to reflect later changes in taxonomy, to ensure alphabetical order of genera, and to remove apparent errors.