List of the world's 100 worst invasive species

This is a list of 100 of the "worst" invasive species in the Global Invasive Species Database, as of 2014^[update]. The IUCN Invasive Species Specialist Group (ISSG), which maintains the list, acknowledges that it is "very difficult to identify 100 invasive species from around the world that really are 'worse' than any others."

Two criteria were used in selecting items for the list:

According to the ISSG, "only one species from each genus was selected. Absence from the list does not imply that a species poses a lesser threat."

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