What is an invasive species?

Invasive species are species that have been introduced, generally by human intervention, outside their natural range and whose establishment and spread can threaten native ecosystem structure, function and delivery of services.

Once introduced, control, management and eradication where possible of invasive species can be very difficult and costly; therefore early detection and reactive measures are desirable.

Below are detailed definitions from the Convention on Biological Diversity – COP 6 Decision VI/23 ‘Alien species that threaten ecosystems, habitats or species’.

1. “alien species” refers to a species, subspecies or lower taxon, introduced outside its natural past or present distribution; includes any part, gametes, seeds, eggs, or propagules of such species that might survive and subsequently reproduce;
2. “invasive alien species” means an alien species whose introduction and/or spread threaten biological diversity ;
3. “introduction” refers to the movement by human agency, indirect or direct, of an alien species outside of its natural range (past or present). This movement can be either within a country or between countries or areas beyond national jurisdiction;
4. “intentional introduction” refers to the deliberate movement and/or release by humans of an alien species outside its natural range ;
5. “unintentional introduction” refers to all other introductions which are not intentional, and
6. “establishment” refers to the process of an alien species in a new habitat successfully producing viable offspring with the likelihood of continued survival
7. “risk analysis” refers to: (1) the assessment of the consequences of the introduction and of the likelihood of establishment of an alien species using science-based information (i.e., risk assessment), and (2) to the identification of measures that can be implemented to reduce or manage these risks (i.e., risk management), taking into account socio-economic and cultural considerations.

For a searchable database of definitions please visit the Convention on Biological Diversity (CBD) Glossary of Terms web page: http://www.cbd.int/invasive/terms.shtml