Invasive exotic species in Switzerland
are invasive plants
is an orchard-eating bacteria
Harmful species invasions spared Europe for a long time. No one is sure why, but scientists think it is linked to the fact that Europe has witnessed less immigration than regions like America or Australia, and was therefore less exposed to the accidental introduction of invasive species. It is also possible that european ecosystems are more stable and therefore less vulnerable to invasive species.
But, with the impact of mondialization, which made migrations easier, the threat of invasive species is spreading in european countries as well. One must not underestimate this threat. One of the more visible consequences is uniformisation: it leads to the loss of unique landscapes, notably in Switzerland. Native species are gradually replaced by exotic species, which end up constituting the majority of the biomass in some systems.
The situation in Switzerland is comparable to other countries in Europe, but it also has some specificities: as an alpine, landlocked country, it has unique ecosystems that need to be protected. Scientists, together with associations like NNF, recommand the rapid implementation of strategies on a national scale. It is a matter of prevention (informing the public, closely watching risky species) and eradication.
All of the signatory countries of the Convention of Biological Diversity, including Switzerland, committed to prevent the introduction, to control or to eradicate exotique species which threaten ecosystems, habitats and native species. What are these species? What measures did Switzerland implement? What is the role of NNF?
Clic on each of these swiss invasive species to learn more about their mode of introduction, the harm they cause and the means to implement to limit their harmful effect.
Scientific name: Procambarus clarkii
Introduction: originally from Central America. Introduced in the 1970's as a pet in gardens and ponds and as food.
Environmental consequences: competition for space and ressources with native species, vector of the crayfish plague.
Economical consequences: the crayfish plague led to important money loss for farmers.
Possible management: Priority is to avoid a larger expansion, specifically by limiting importation. Eradication can be a solution, but it could endanger other species, since the most common methods are pesticids and fishing. The threat could be contained this way, but the effort must be continuous.
Scientific name: Trachemys scripta elegans
Introduction: originally from North America. Farmed and sold as pets, they are often released in the wild by their owner, or escape from gardens.
Environmental consequences: competition with native turtle, and harmful effect on the amphibans and birds (they destroy nests and feed on the eggs.)
Economic consequences: insignificant.
Possible management: Laws forbidding releasing must be reinforced. It is also necessary to educate the owners to environmental risks.
Introduction: originally from Southern Europe. Intrduced for esthetic reason in the XVIth century.
Environmental consequences: dense stands outcompete native species and this will reduce the biodiversity of invaded sites.
Economic consequences: insignificant
Possible management: cutting doesn't appear as a good solution because it has the tendancy to increase sprout productivity. Information must be found on control methods.
Scientific name: Anoplophora glabripennis
Introduction: originally from China and Korea. Introduced in Europe as larvae and eggs, probably in wooden boxes and pallets from Asia.
Environmental consequences: the beetle harms forests by infesting trees.
Economical consequences: the cost of its eradication and the loss due to the damages inflicted to trees are very important.
Possible management: the main way to get rid of the beetle is to eradicate it by cutting the infested trees. The possibility of biological control is currently being studied.
Introduction: at the beginning of the XXth century, the muskrat was farmed for its fur. Its expansions probably comes from specimens which escaped from those farms.
Environmental consequences: the muskrat feeds on rare plants and mussels, which led to the decrease in population of endangered species.
Economic consequences: this invasive species has an very important economical impact because of its burrowing activities. It damages canal banks and can cause floods. Moreover, it spreads diseases, which causes public health issues.
Possible management: hunters hired by the government try to control the invasion, but funding is not sufficient.
Introduction: originally from North America. Introduced in Europe for aesthetic reasons.
Environmental consequences: this predator feeds on planton, invertebrates and fish eggs. Its presence, if it is too important, can therefore alter ecosystems.
Economic consequences: insignificant.
Possible management: regulations to forbid owners to release pumpkinseeds in the wild must be reinforced. Programs to educate people must also be implemented.
Scientific name: Sciurus carolinensis
Introduction: originally from North America. Introduced in Great Britain then in Italy for esthetical reasons, and to enrich diversity.
Environmental consequences: competition for space and ressources with the red squirrel, which is now endangered.
Economical consequences: insignificant.
Possible management: Many people oppose the total eradication of the grey squirrel, which doesn't appear as the best solution. However, protection zones for the red squirrel must be constructed, and the grey squirrel, banished from them.
Introduction: originally from the Black Sea area. It was introduced in Europe through human-mediated transport, mainly by attaching to boats. Its developement was important in the XIXth century, because of the developement of canals.
Environmental impact: competition for space and ressources with native mussels. They alter the balance of ecosystems because they feed on plancton. Their number can increase rapidly: in the Rhine, 11000 specimens by square meters have been recorded.
Economical impact: mussels attach to pipes, which can clog them or lead to quicker erosion.
Possible management: eradication methods have been implemented to avoid damages caused to human infrastructures, such as power stations. However, control in natural habitats must be reinforced, to prevent the mussel from colonising new territories.
Scientific name: Fallopia japonica
Introduction: originally from Japan and Northern China. Sold in the XIXth century as an ornament.
Environmental consequences: The knotweed prevent native species from growing: its dense foliage leads to a lack of sun for ground flora. In winter, when foliage disapears, the bare exposed soil is easily washed away, increasing soil erosion, especially on steep riverbanks.
Economical consequences: the knotweed's roots can grow trough pavement, which damages constructions.
Possible management : eradiction through peticides or uprooting is possible, but it causes several problems. First, the knotweed is a very volatile plant, the risk of reinfestation is therefore quite high if all cut material are not safely disposed of. Then, uprooting leads to a deeper erosion of soils. It must therefore be accompanied by replanting native plants. A long term program must be implemented.