Indicator biodiversity

Invasive alien species

Plants, animals, fungi and microorganisms that have been transferred outside their natural range through human activities qualify as “alien”. Their transfer may be intentional (voluntary or deliberate introduction) or accidental (involuntary or unintentional introduction). Alien species that are known or must be assumed to be spreading into Switzerland and can cause damage to biodiversity and its sustainable use or endanger humans or the environment qualify as “invasive”.  

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.

Assessment of the state
poor poor
Assessment of the trend
negative negative
Potentially invasive alien species (Watch List)* 2014: 17 Invasive alien species (Black List)* 2014: 41 Potentially invasive alien species (Watch List)* 2013: 22 Invasive alien species (Black List)* 2013: 23 Potentially invasive alien species (Watch List)* 2006: 28 Invasive alien species (Black List)* 2006: 20
* Plants only at present

Data for the graph: Excel
Source: Infoflora

Of the 825 established alien species known in Switzerland (plants, animals, fungi), 107 are classified as invasive. Among the cases surveyed (plant species only up to now), their number has risen continuously in recent decades. The Black List of invasive alien plants contains 41 species, twice more than in 2006. At the same time, the number of potentially invasive species (Watch List) has decreased. The reasons for this are: first, species that did not yet occur in Switzerland in 2006 have been included on the latest Black List; second, some species included on the Watch List in 2006 are now on the Black List. With a 21% increase in the number of invasive or potentially invasive plant species, the development must assessed as negative.

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.

International comparison

Other countries (e.g. Germany, Norway) keep black 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 federal data centres are based on detection reports and are not recorded systematically. To enable the definition of the spread and damage potential, the detection reports and species ecology are evaluated by experts.

The "Black List“ includes invasive alien species in Switzerland that cause damage to biodiversity, health or the economy and whose spread must be prevented. The "Watch List“ includes invasive alien species in Switzerland that may cause damage and whose spread must be monitored.  Allocation to the lists is based on expert assessments according to their spread potential, an evaluation of the damage, and the methods and cost of the prevention efforts.

Basis for assessment of the trend
Targeted trend Initial value Final value Variation in % Observed trend Assessment
Decrease 2006 2014 20.83% Growth negative
Last updated on: 29.09.2020

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