The Swedish University of Agricultural Sciences (SLU) has conducted a review of over 5,500 species and found 451 that are classified as posing a high or very high risk. This is significantly more than in the previous review, which was published in 2018.
It's a bit scary that we've got so many more species that can cause problems since last time, it's happening very fast, says Mora Aronsson, method manager for risk classification at SLU's Species Data Bank.
A warmer climate is one of the reasons behind the increase. This means that more species can establish themselves and spread, even northwards in the country.
"Lost year"
One problem is that 2023 was a bit of a lost year in the fight against invasive species. Then, the state funds for combating invasive species were withdrawn. They returned in 2024, but the County Administrative Boards are lagging behind, says Mora Aronsson.
He says that many municipalities, organizations, and authorities are doing a great job.
The Swedish Transport Administration is working extensively to remove, among other things, Japanese knotweed that grows under railway embankments and road banks and undermines them.
Garden plants
The new risk list shows that garden plants are becoming an increasingly large problem. One example is the butterfly bush, which is becoming increasingly common in southern Sweden.
It has been marketed as beneficial for butterflies, but it has become a bit like a new lupin, spreading and outcompeting other plants.
In addition to invasive species displacing other vegetation and animals, they also have economic consequences when they destroy environments, such as those near roads and railways. They can also be hosts for diseases that affect native species.
Those who discover an invasive species can report it to, for example, artportalen.se.
Invasive species can have a significant negative impact. Through early detection, both ecological damage and economic costs can be reduced, says Mora Aronsson.
Examples of species that can pose a very high risk:
• German buckthorn
• Alpine knotweed
• Horse chestnut
• Giant hogweed
• Giant balsam
• Butterfly bush
• Japanese knotweed
• Killer snail
• Zebra mussel
• Oyster disease
• New Zealand mud snail
The risk assessment is based on two main components: invasion potential and ecological effect. A species' invasion potential is determined by its ability to establish viable populations and spread. The ecological effect is determined by the effect the species can have on native species and natural habitats.
Source: SLU
