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".

The threat grows with globalisation of trade

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 problem

The problem of invasive alien species is global. It is also considered as thesecond 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). It leads to huge economic losses, especially for the fishery sector, forestry or agriculture. A recent analysis at the European level has calculated this loss at 12 billion Euros.

A list (Global invasive species database) of the 100 most harmful species to the environment (mammals, birds, insects, molluscs, fungi, etc.) has also been established on a global scale. Among these one finds species that are threatening to Europe such as the Tiger mosquito (Aedes albopictus), nutria (Myocastor coypus) or bullfrog (Lithobates catesbeianus = Rana catesbeiana).

Required international and european response

The Convention on Biological Diversity (1992 ) is the ultimate international benchmark for the integrated management of this problem. However, it contains enough general requirements that need to be specified at a more regional or local level. It requires that each State, including Belgium, take the following actions to the extent possible: prevent the introduction of, control or eradicate those alien species that threaten the ecosystems, habitats or species (Article 8 h).

In 2010, the more specific policy objectives ("Aichi targets") were adopted for the protection of biodiversity during the Conference of Parties meeting in Nagoya (Japan). The ninth objective states that "By 2020, invasive alien species and pathways are identified and prioritised, priority species are controlled or eradicated, and measures are in place to manage pathways to prevent their introduction and establishment".

The European Union is taking action at its level. Since 2015, a regulation has organised the prevention and management of the introduction and spread of exotic invasive species in the Member States of the Union.