Invasive alien species is a living organism (animal or plant) that has been introduced by humans, either intentionally or unintentionally, outside its natural place of existence. It is called "invasive" as it adapts to its new environment while causing significant damage to the biodiversity or to the natural habitats. It is also sometimes called "invasive species".

A growing threat 

Historically, alien species have been introduced in Europe. However, all are not invasive. This may be because either they are not threatening to the ecosystem, or because they cannot adapt and thus are unable to reproduce. Their introduction, if well controlled by humans, is sometimes considered beneficial. Consider, for example ornamental gardens for plants or zoological parks for animals.

But today, the threat to the environment is real. It is even more acute than ever before because of considerable increase in trade and strong demand for exotic animals and plants. Sometimes the introduction of these exotic species into nature also causes health problems for humans and/or health problems for domestic or "native" (those that live naturally in the wild here) animals.

A global issue

The problem of invasive alien species is global. It is also considered as the second leading cause of loss of biodiversity worldwide after the loss of natural habitats (e.g. due to the conversion of these habitats into agricultural areas, industrial areas or areas for human habitation). 

These species in fact contribute to the loss of European biodiversity and the degradation of the ecosystem services that it provides. How? For example, by entering into competition with the native species (indigenous/native species) for food or for the use of the natural habitat but also by feeding or by hybridising with them. Diversity of the native species is thereby reduced, particularly in terms of genetic diversity.

Economic loss

In addition to the purely environmental aspect, the IAS also cause major economic damage currently estimated at €12.5 billion per year for the European Union only. They can cause direct economic losses in certain sectors such as agriculture, aquaculture, fishing or forestry, through, for example, the introduction of diseases. Their control and elimination may also result in significant costs that must be borne collectively by the society.