Arctic environments like Svalbard are especially vulnerable, and alien species that gain a foothold can have severe consequences for native habitats. In 2018 an increasing number of alien species were risk-assessed for Svalbard. The majority of these are door knocker species.

Observing examples from other places in the world we know that alien species that come to the Arctic are difficult to combat when they have first become established. It is therefore important to be particularly aware of door knocker species that might gain a foothold in Svalbard in the near future.

More species included in the new ecological risk-assessment

The Norwegian Biodiversity Information Centre has assessed the ecological risk for alien species in Norway. For Svalbard, in 2018, far more species were included than previously. As well as vascular plants and mammals, which were risk-assessed in 2012, fish and marine invertebrates were also now included.

Many of the risk-assessed species are door knocker species

Of the 47 species in total which are risk-assessed for Svalbard, 31 are what we call door knocker species. These species have not yet become established on Svalbard, or in the Fishery Protection Zone around Svalbard, but they are thought to be able to do so within 50 years.

A total of 23 of the 24 marine invertebrates assessed for Svalbard are door knocker species, as well as 5 of the 19 vascular plants. Two door knocker species, the crustacean Ischyrocerus commensalis and red king crab Paralithodes camtschaticus, are assessed as high impact and severe impact risk respectively. Most of the door knocker species are nevertheless assessed as having a low impact risk.

Come as stowaways

Alien species can come to Svalbard by different means. Svalbard is an island group, so terrestrial ecosystems are essentially well-protected. However, increased globalisation and the travel industry, combined with growth in the popularity of nature tourism, means that species disperse over long distances. Tourists might have seeds, eggs, or larvae attached to hiking clothes, shoes or fishing tackle. "Stowaways" can also travel the same way in luggage, imported goods and soil, or attached to the hull of ships.

In addition, it is thought that alien species might arrive in Svalbard via secondary introduction. This involves alien species present in neighbouring countries expanding their distribution area and crossing into the Norwegian zone. As Svalbard is an archipelago, species that might arrive via secondary introduction are first and foremost marine species that disperse in the ocean waters or along the bottom.

What does ecological risk mean?

The assessments of ecological risk are based on quantitative assessments of the invasion potential and ecological effect of the species. Invasion potential refers to the viability of a species combined with how rapidly it disperses, whereas the ecological effect is to what degree the species can negatively influence native species and nature types. The combination of invasion potential and ecological effect determines the risk category for the species.

Marine species with high ecological risk

Snow crab Chionoecetes opilio, red king crab Paralithodes camtschaticus and the tiny amphipod species Ischyrocerus commensalis are all assessed as having a severe impact risk. If an alien species establishes itself on Svalbard, or in the marine areas around Svalbard, it can have a range of different consequences for local nature.

Snow crab is native to the Bering Sea but appeared in the Barents Sea in 1996 where it spread and became abundant in the subsequent years. In 2018, two assessments were carried out for snow crab, one for Svalbard and one for mainland Norway. The species is assessed as having a severe impact risk for the marine areas around Svalbard, while in the Norwegian Economic Zone outside Finnmark and Troms, it is assessed as having a potentially high impact.

The snow crab feeds on bottom-dwelling species and is likely to have a severe negative effect on keystone species and ecosystems.

Alien species can also carry parasites. One example is Crangon crangon, often called the common shrimp. It is widespread along the entire Norwegian coast and can probably become established on Svalbard, especially if the ocean temperature rises due to climate change. The common shrimp Crangon crangon is a vector for the dinoflagellate Hematodinium sp., a parasite that can be transmitted to local species of crabs and shrimps. Local species are not adapted to this parasite and are likely to be weakened, at the same time as Crangon crangon gains a competitive advantage.

What are the negative effects of alien vascular plants?

Among the vascular plants, 9 of the 19 assessed species comprise a risk.

Cow parsley Anthriscus sylvestris has been observed on in the settlement of Barentsburg, on several occasions, since 2007 and to the present day. The species is known for being difficult to eradicate once it has become established. The risk is first and foremost connected to the species establishing itself in the nutrient-rich, bird nesting cliff nature reserves. Cow parsley outcompetes other species on the bird cliffs of the Norwegian mainland and there is good reason to suppose that the same will occur on Svalbard. In contrast to local plant species, cow parsley is able to provide camouflage for the Arctic fox Vulpes lagopus, which can also have a negative impact on birds.

Consequences of climate change for Svalbard's nature

The climate of Svalbard is tough and the ecosystems are composed of species that are especially adapted to its demands. One of the most important reasons that the majority of alien species of vascular plants are assessed as being a low impact risk is that, unlike the local flora, they are unsuited to the climate.

Yet, what will the future bring? It is expected that human activity on Svalbard will increase, so that the frequency of unintended introductions will increase. At the same time, it is expected that the climate will become warmer, which will increase the invasion potential of alien species at the same time as it will weaken the competitive advantage of local species.