Invasive alien species (IAS) are non-native species whose introduction and/or spread outside their natural, past or present, ranges pose a threat to biodiversity.
Invasive alien species occur in all major groups, including animals, plants, fungi and micro-organisms, and are considered, at least on islands, to be the second most important reason for biodiversity loss worldwide (after direct habitat loss or destruction).
About 10 000 alien species have been registered in Europe. Some of these species were introduced on purpose and remain economically important. However, a proportion of the alien species established cause significant damage to native biodiversity and can be classified as invasive alien species according to the Convention on Biological Diversity.
Invasive species can cause great damage to native species by competing with them for food, eating them, spreading diseases, causing genetic changes through inter-breeding with them and disrupting various aspects of the food web and the physical environment.
There is an upward trend in the establishment of new species, with impacts on biodiversity expected to increase because of the growing number of species involved, and an increasing vulnerability of ecosystems to invasions, which results from other pressures such as habitat loss, degradation, fragmentation, over-exploitation and climate change.
Globalization, particularly increased trade and tourism, have resulted in an upsurge in the number and type of alien species arriving in Europe. Marine and coastal areas are being drastically affected as a result of increased shipping and the building of canals between isolated seas. In order to gain better understanding of invasive alien species and their impact on European biodiversity a list of the worst invasive alien species threatening biodiversity in Europe has been established. The list currently contains 163 species or species groups.
Map 1 Number of the listed 'worst' terrestrial and freshwater invasive alien species threatening biodiversity in Europe
Note: The numbers on the map indicate how many species from the list are present in each country (e.g. out of 163 'worst' invasive alien species, 34 are present in Portugal).
- EEA technical report: The impacts of invasive alien species in Europe
- EEA technical report: Invasive alien species indicators in Europe - a review of Streamlining European Biodiversity (SEBI) Indicator 10
- EEA technical report: Towards an early warning and information system for invasive alien species (IAS) threatening biodiversity in Europe
- EEA report: Late lessons from early warnings: science, precaution, innovation; Chapter 20 Invasive alien species: a growing but neglected threat?
- IEEP report: Assessment to support continued development of the EU Strategy to combat invasive alien species
- Proposal for a Regulation of the European Parliament and of the Council on the prevention and management of the introduction and spread of invasive alien species
- European Strategy on Invasive Alien Species
- Code of Conduct on Horticulture and Invasive Alien Plants
- Alien species and nature conservation in the EU: The role of the LIFE programme