100 of the World's Worst Invasive Alien Species

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Welcome to "One Hundred of the World's Worst Invasive Alien Species", funded by La Fondation TOTAL, and part of the Global Invasive Species Database. Invasive species have been recognised globally as a major threat to biodiversity (the collected wealth of the world's species of plants, animals and other organisms) as well as to agriculture and other human interests.

It is very difficult to identify 100 invasive species from around the world that really are "worse" than any others. Species and their interactions with ecosystems are very complex. Some species may have invaded only a restricted region, but have a high probability of expanding and causing further great damage (e.g. see Boiga irregularis: the brown tree snake). Other species may already be globally widespread, and causing cumulative but less visible damage. Many biological families or genera contain large numbers of invasive species, often with similar impacts.

Species were selected for the list according to two criteria: their serious impact on biological diversity and/or human activities, and their illustration of important issues surrounding biological invasion. To ensure the inclusion of a wide variety of examples, only one species from each genus was selected. Absence from the list does not imply that a species poses a lesser threat. For any queries to do with this database, please contact: issg@auckland.ac.nz

2013 Update

Rinderpest virus a species of morbillivirus causing cattle plague, a highly fatal viral disease of domestic cattle, buffaloes and yaks was listed as one of the '100 of the World's Worst Invasive Alien Species'. Rinderpest virus was declared eradicated in the wild in 2010.

A global survey was conducted in 2013 to nominate a replacement for the Rinderpest virus on the '100 of the World's Worst Invasive Alien Species' list. Over 650 invasion biologists participated in the survey. The floating aquatic fern Salvinia molesta gained the most votes and was selected to replace the Rinderpest virus. The results are published in Nature- see Alien species: Monster fern makes IUCN invader list*.

Salvinia molesta thrives in slow-moving, nutrient-rich warm freshwater. A rapidly growing competitive plant, it is dispersed long distances within a waterbody (via water currents) and between waterbodies (via animals and contaminated equipment, boats or vehicles). S. molesta can form dense vegetation mats that reduce water-flow and lower light and oxygen levels in the water. This stagnant dark environment negatively affects, the biodiversity and abundance of freshwater species, including fish and submerged aquatic plants. S. molesta can alter wetland ecosystems and cause wetland habitat loss. Salvinia invasion also poses a severe threat to socio-economic activities that are dependent on open, flowing and/or high quality waterbodies, including hydro-electricity generation, fishing and boat transport.

*Luque GM, Bellard C, Bertelsmeier C, Bonnaud E, Genovesi P, Simberloff D, Courchamp, F (2013) Alien species: Monster fern makes IUCN invader list. Nature, 498, 37