Distribution map


100 of the World’s Worst IAS



Giant aquatic fern added to the IUCN Invasive Species list

The Giant Salvinia (Salvinia molesta), an aquatic fern has been added to the list of 100 of the World’s Worst Invasive Alien Species. Compiled by the IUCN Species Survival Commission Invasive Species Specialist Group (ISSG), the list aims to increase awareness about invasive alien species and to help prevent further invasions.


Recently the rinderpest virus was removed from the list and a review was conducted to decide which invasive species should be added. The review involved more than 650 experts from 63 countries. More than 10,000 invasive species were assessed in terms of their capacity to spread and their potential ecological or economic impact.


Native to Brazil, the Giant Salvinia is a floating aquatic fern that thrives in slow-moving, nutrient-rich, warm, freshwater. A rapidly growing competitive plant, it has spread throughout the tropics and subtropics. It doubles in abundance within days, forming dense, floating mats that reduce water-flow and lower the 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. Its spread can also impede water-based transport and clog irrigation and power generation systems.


By being added to the list it is hoped that this heightened focus on the species will increase awareness and stimulate more conservation action to reduce its impact, and more in general on the severe impacts caused by biological invasions worldwide.


The full list of the World’s Worst Invasive Species can be viewed here:


The review was featured in an article published in Nature (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)


For more information please visit the IUCN website:
or contact Dr Piero Genovesi This e-mail address is being protected from spambots. You need JavaScript enabled to view it