What are Invasive Alien Species?

An alien species is a non-native species that does not naturally inhabit a certain ecosystem, but has been introduced, or may be introduced there deliberately or accidentally. Non-native, exotic or introduced species are all synonyms for alien species. If the introduction or the spreading of alien species affects biodiversity, human health or causes economic damages in the area it inhabits, we call it invasive alien species (IAS).

Today, the presence of invasive species in a certain area, along with the direct destruction of habitats, represents the highest threat to that areas biodiversity. The accelerated growth of commerce, transportation and traveling in the 20th century had a consequence – the spreading of species and a strong and constant growth of the number of species introduced in new regions. The introduction of invasive species or biological invasion is not, however, a modern day invention. Large human migrations, commerce and transportation have always been followed by the spreading of species outside the area of their natural distribution. The problem of invasive species is constantly growing since the discovery and colonization of the New World and represents one of the main threats in biodiversity conservation today.

The control of invasive species and the reduction of their influence on native species and complete ecosystems represent one of the greatest challenges in Europe’s nature conservation today. An invasive alien species is almost never possible to remove from a habitat that it expanded to, except maybe in islands or limited parts of land. It is therefore important to discover the presence of a potentially invasive alien species in an ecosystem very early, while urgent measures regarding spreading control and removal are the only effective measures in fighting them.

Cutleaf Coneflower (Rudbeckia laciniata), photo: archive of SINP