Explanation:

Alien species – a species that has been intentionally or unintentionally introduced to a location, area, or region where it does not occur naturally.

 According to the Convention on Biological Diversity (CBD) “Alien species” refers to a ‘species, subspecies or lower taxon, introduced outside its natural past or present distribution; including any part, gametes, seeds, eggs, or propagules of such species that might survive and subsequently reproduce’. Synonymous terms such as non-native species or non-indigenous species are more precise and should be used in preference to terms as introduced, exotic, feral, foreign, ornamental or weedy species.

Invasive species – a species that has established and spread – or has the potential to do so – outside of its natural distribution range, and which then threatens ecosystems, habitats and/or other species, potentially causing economic and/or environmental damage, or harm to human health. The majority of invasive species are alien, but it is important to note that native species may also become invasive, usually under altered environmental conditions such as grazing, cyclones, changes in nutrient regimes, colonisation by an invasive species, or other alterations