Invasive alien species
Plants, animals, fungi and microorganisms that have been transferred outside their natural range through human activities are termed ‘alien’. They may be transferred intentionally (voluntary or deliberate introduction) or accidentally (involuntary or unintentional introduction). Alien species are termed ‘invasive’ when they are known to or can be expected (‘potentially invasive’) to impair biological diversity, ecosystem services and their sustainable use or to endanger human beings and the environment by spreading in Switzerland.
Invasive species contribute to the decline in biodiversity throughout the world and are the second most important cause of global species decline after habitat destruction. The increase in alien species is caused by the intensification of global trade and travel.
Of the around 1,300 established alien species known in Switzerland (plants, animals, fungi), 197 are classified as invasive. Studies show that this number has risen continuously in recent decades; there has been an increase of about 50% over the past 30 years (1990–2020), a clearly negative trend.
The observations made in Switzerland in recent decades reveal continuous growth not only in the number of invasive alien species, but also in the size of the areas where they occur. Nevertheless, the invasive alien species in Switzerland are still in a relatively early stage of spreading when compared internationally. This means that if we do not take action, these species will colonise larger areas and cause even more damage. It can be safely said that the potential damage caused by the continuing spread of invasive alien species will cost much more than the measures we can take today to prevent them.
Other countries (e.g. Germany, Norway) and EU also keep lists of invasive species from different taxonomic groups. Standardised classification criteria have not been defined up to now, hence the comparability of the lists is limited.
The data provided by the Swiss Information Centre for Species (InfoSpecies) are based on detection reports and are not recorded systematically. The detection reports and species ecology are evaluated by experts in a standardised manner for all taxonomic groups in order to determine the extent of spread and damage potential.
The list of invasive alien species was compiled on the basis of the classification of ecological damage as transferable to Switzerland according to EICAT, a classification system proposed by the IUCN as a global standard.
|Targeted trend||Initial value||Final value||Variation in %||Observed trend||Assessment|
|Decrease||Average 1990-1992||Average 2018-2020||48.84%||Growth||negative|