Lists of worst invasive species

Worst invasive species is a somewhat subjective term as it depends on who you are asking and where they are.

• A list of the worst 100 invasive species  was published in 2000 and revised in 2004 by the ISSG in conjunction with peak biodiversity body the  IUCN
• The IUCN/GISD/ISSG brought out a revised version in 2022 - Global Invasive Species Database (2022).  It can be downloaded from
  http://www.iucngisd.org/gisd/100_worst.php
• In 2020, the European Union published the most recent list (Invasive alien species of Union concern) for EU member countries, backed by EU laws. It can be downloaded from https://ec.europa.eu/environment/nature/invasivealien/list/index_en.htm

Environmental Impact Classification for Alien Taxa (EICAT)

The definition of EICAT according to the GISD -

EICAT is the IUCN Standard for the classification of impacts of alien taxa on the environment. It is a simple, objective and transparent method that classifies alien taxa into one of five impact categories, according to the magnitude of the detrimental impacts on native biodiversity.
Each of these five impact categories represents a different impact magnitude, depending on the level of biological organisation of the native biota impacted (individual, population or community) and the reversibility of this impact. ¹

Note the similarities between EICAT and the Redlist Cliassification of Endangered species.

Examples of EICAT in action

• Application of the Environmental Impact Classification for Alien Taxa (EICAT) to a global assessment of alien bird impacts
• Ranking alien species based on their risks of causing environmental impacts: a global assessment of alien ungulates

Dig Deeper

• What is an ecosystem?
• ecosystem definition
• What is ecology?
• Ecosystems
• IUCN Standard to support global action on invasive alien species
• Environmental Impact Classification for Alien Taxa (EICAT)