Terms and definitions

Alien species are organisms that have spread from their natural distribution range to a new area through human action, whether intentionally or unintentionally. In other words, an alien species has migrated over natural barriers to migration (such as a continent, a sea or a mountain range) with intentional or unintentional human assistance. Generally alien species adapt poorly to their new environment and are quickly destroyed. In some cases, however, alien species thrive in their new environment, establishing a permanent and propagating population.

Invasive alien species are alien species that cause obvious harmful impacts.  A few of alien species thrive remarkably well, so much so that they cause severe damage to indigenous species, ecosystems, crops, forestry or other areas of the economy and thus pose a serious threat. They may also cause significant financial damage by affecting human, animal or plant health or by decreasing the value of properties, or by causing social or aesthetic harmful impacts.


The terms ‘alien species’ and ‘invasive alien species’ as defined in the Convention on Biological Diversity (CBD) (Glossary of Terms), in the EU (European Commission Communication “Towards an EU Strategy on Invasive Species”, 2008), in the International Plant Protection Convention (IPPC) (Glossary of Phytosanitary Terms) and in the Global Invasive Species Programme (GISP). See also FAO Phytosanitary Glossary.

  Finnish term CBD EU IPPC GISP
Alien species Vieraslaji Species, subspecies or lower taxon, introduced outside its natural past or present distribution. Includes any part, gametes, eggs, or propagules of such species that might survive and subsequently reproduce. An alien species is a species that is deliberately or unintentionally introduced outside their natural habitats where they establish, proliferate and spread. An alien species is an individual or population, at any life stage, or a viable part of an organism that is non-indigenous to an area and that has entered by human agency into the area.  
Invasive alien species Haitallinen vieraslaji An alien species whose introduction and/or spread outside its natural past or present distribution threaten biological diversity. An invasive alien species is a species whose introduction and/or spread threaten biological diversity. An invasive alien species is an alien species that by its establishment or spread has become injurious to plants, or that by risk analysis is shown to be potentially injurious to plants. An alien species whose appearance and spread threaten ecosystems, habitats or species by causing economic or environmental harm.

Table source: the national strategy, Table 2, page 36.