1. What is an invasive species?
There is a difference between an alien species and an invasive species.
Alien species are those that have been moved from their natural environment by humans. Sometimes they become harmless in their new location - but sometimes they spread uncontrollably and cause major problems. Then they are called invasive.
2. Why are they a problem?
The colorful flowering lupines that line many kilometers of roadsides may seem magnificent. They may crowd out daisies, strawberries, bluebells, and other native flowers - but does it really matter?
The takeover of species like lupines not only leads to a more narrow diversity of plant species, it can affect entire ecosystems. When native flowers disappear, many insects have a harder time - and in the case of lupine, it can affect the entire vegetation by fixing more nitrogen, "fertilizing" the soil to the detriment of many native plants.
Lupine is just one of thousands of examples of how nature is affected by the spread of new species. Invasive species have been identified as one of the top five threats to biodiversity - on which humans depend for food, clean water and fresh air to breathe.
Invasive species can also spread disease, such as the signal crayfish, which has brought crayfish plague to Sweden, which is devastating to native crayfish.
They can be costly to society and to individuals, who may have to pay to remove a troublesome species from their land. Conditions for forestry, agriculture and fishing can be seriously damaged, as can those who spend time in the forest and countryside, as access to nature may have to be restricted.
3. Haven't we always introduced new species to Sweden?
Yes, both intentionally and unintentionally. But increased travel and global trade mean that we are bringing new species here to a completely different extent than before - and the number of alien species that become invasive is steadily increasing. The aggressive blackmouth goby, which hitchhiked here in the ballast of ships, is one of many examples. It eats the roe and fry of other fish and can outcompete native species such as flounder.
In addition, climate change is making it easier for cold-hardy animals and plants to thrive further north, with some becoming invasive. Japanese knotweed and the Spanish slug are among those that may find it easier to establish themselves further north as temperatures rise, which could have "unpredictable consequences" for biodiversity, according to the Swedish Environmental Protection Agency.
4. How many are there in Sweden?
A total of 257 alien species in Sweden have been classified as having a high or very high risk of becoming invasive.
There is also an EU list of invasive alien species containing 88 species, 25 of which are found in Sweden. The listed species are considered so problematic that their possession and handling is prohibited in all EU countries. In addition, the Swedish Environmental Protection Agency and the Swedish Agency for Marine and Water Management have proposed to add 41 non-EU species to a national list, which would be subject to the same prohibitions as the EU-listed species. Flowering lupine, Japanese knotweed and blackmouth goby are some of them.
5. What can I do to help?
According to the authorities, we can all do our part to limit the spread of invasive species. Much has to do with what we do in our gardens, with exotic pets, and when fishing.
For example, you should never throw plant debris or compost into the wild, as it may contain invasive species. It is also not a good idea to bring seeds or plants from other countries.
Recreational boats can spread aquatic invasive species, for example, by turning the hull of the boat into a breeding ground or the hard water into a pool for them. That's why you should clean your boat and pump out the water before using it in a new location, says the Swedish Agency for Marine and Water Management. Fishing equipment should be cleaned if it is to be used in a new body of water, and you should not bait it with fish or other items from other waters.
