Controlling invasive species

Controlling invasive species
Ambrosia - one of the best known invasive species. © Martin Richter/

Involved sectors

Agriculture, Forestry, Water management, Hunting, Nature protection, Local population/citizens

Affected habitats

Forest, Shrubs and wooded areas, Bogs and fens, wetlands, Alpine habitats, Grassland, Arable land, Areas for settlements and transport, Waterbodies


Invasive species are alien plants and animals that have negative impacts on other species, biological communities or biotopes and thus pose a threat to biodiversity. Invasive species may also cause economic problems (e.g. when present as weeds) or health problems (such as allergies and diseases). Hybridisation with native species can also occur. In Switzerland, 107 alien species are classed as problematical, including mammals, birds, reptiles, amphibians, insects and plants. When dealing with alien species and adopting measures to limit them, prevention, monitoring, acceptance, surveillance and control all have a role to play. In the context of ecological connectivity, particular account must be taken of invasive species as they are able to use the emerging connecting bridges in the landscape to penetrate into new areas. In the case of invasive neophytes, this applies especially to stream margins and riparian zones (distribution along collapsed river banks and via erosion and flooding), which, as natural connecting elements in the landscape, are also important elements of the biotope network.


Ecological impact  
Improvement or preservation of habitats Awareness of the impacts of invasive species is required, justifying control measures (e.g. specific threat posed to rare or endangered species, risk of penetration of invasive species into new areas).
Element of ecological network Control measures constitute major intervention and generally entail considerable effort as well as damage to other species (e.g. scarification as a result of root removal)
Other Measures should only take place if it is certain that the habitat concerned can be restored to a stable ecological state following the measure and its long-term conservation in this state is guaranteed.
Time of realisation for measure Years: The duration of measures until the attainment of an effect is difficult to estimate and depends substantially on the species concerned and the measures taken.
Impact scope Very localised (plot): The impact of measures is very limited in spatial terms.


Implementation period Months: Here too, many different measures and implementation periods are possible.
Frequency Recurring: Generally long-term strategies are needed to fight invasive species effectively.

Economic and legal aspects

Costs High (100'000-1 Mio EUR): Very variable. Cost of controlling all stocks of Japanese Knotweed in Germany, for example, is € 6.2 mill. + € 16.7 mill. for subsequent stabilisation of river banks.
Socio-economic impacts Medium: High costs of control can be set against the very substantial economic impacts associated with alien species, estimated at USD 13.8 billion p.a. in the US.
Sources of financing Public: local, Public: regional, Public: national, Public: European
Legal situation International treaties, European and national legislation regulate the management of invasive species: Convention on Biological Diversity, Habitats Directive, Birds Directive, federal states' nature conservation legislation, plant protection legislation, hunting legislation.

Further information

Evaluation In view of the many examples, a species-specific perspective must be taken. Comprehensive experience has been gained with various measures to deal with some species (e.g. Japanese Knotweed: mowing, grazing, herbicide use, combined procedures). It is always important to weigh up the relationship between the negative impacts, on the one hand, and intervention and its costs, on the other.
Information Other: Comprehensive information on neophytes in Germany: , Delivering Alien Invasive Species In Europe (DAISIE): , North European and Baltic Network on Invasive Alien Species (NOBANIS): , Report on invasive species in Switzerland: ; aquatic alien species:

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