Species that are not native to an area can displace species that already live there. The Intergovernmental Panel on Nature ( IPBES) considers this to be one of the greatest threats to species diversity on our planet.
Researchers have now catalogued which alien plants may pose a threat to plants in the Arctic. The results are concerning, particularly at a time when it has probably never been easier for alien species to spread.
"We found a total of 2554 species that would find a suitable climatic niche in today's Arctic," says Kristine Bakke Westergaard, an associate professor at the Department of Natural History at the NTNU University Museum (at the Norwegian University of Science and Technology, NTNU).
This means that these plants have a chance of making it in the Arctic if they manage to find a way there. One of the most probable transport mechanisms is hitchhiking on, or with, humans.
"Our results show that alien species from virtually all over the world can find a niche in the Arctic. And with all the human activity in the Arctic now, there are lots of opportunities to get there," Westergaard said.
Data from more than 51 million occurrences
She and colleagues from the Department of Natural History and the University of Liverpool have conducted what is called a "horizon scan".
"We looked at roughly 14,000 known alien plant species that can spread to places where they do not originally belong," Westergaard said.
The researchers used data from over 51 million known occurrences of these species. They found this information in the GBIF—the Global Biodiversity Information Facility , in large databases and in the scientific literature.
First author Tor Henrik Ulsted was a master's student at the NTNU University Museum until 2024. Ulsted won the Faculty of Natural Science's award for best the master's thesis that contributes to sustainable development, and has since worked to publish this article.
Norway a high-risk country
The researchers used the data to create a map that provides an overview of the most threatened areas.
"Our map shows hotspot areas in the Arctic where many alien species can tolerate the climate. The highest number of species are found in the north of Norway," Ulsted said.
While Norway is among the high-risk areas, few, if any, places in the Arctic are completely safe, including Svalbard.
"Even in Svalbard, 86 alien species can find a climatic niche," says Westergaard, who has found and studied alien species there herself.
Conditions in the north are changing rapidly. In recent years, it has generally become warmer in the Arctic, meaning that more and more alien species can find a possible niche where they can thrive.
Tools for those assessing the threat
The Norwegian Biodiversity Information Centre 's expert committees for Norway and Svalbard assess the risk of alien species in different areas.
"These committees have long found it to be very laborious, almost impossible, to make a list of relevant species that should be assessed as possible new alien species," says Westergaard.
The new methodology will help experts in these committees to look at the species lists and assess the ecological risk for each of the species in the relevant areas.
"Our long-term goal is to help identify alien species before they become invasive and problematic," Ulsted said.
It is much more effective to identify and manage invasive species as early as possible rather than waiting until they are well established.
Westergaard says this approach also supports the goals of the Kunming-Montreal Global Biodiversity Framework , among which is reducing the threat from alien species, including by halving the introduction and establishment of alien species by 2030.
It is also in line with several of the measures in the Norwegian authorities' action plan against alien organisms. ( Combating harmful alien organisms – Action plan 2020–2025 in Norwegian)
Reference:
Ulsted TH, Westergaard KB, Dawson W, Speed JDM (2025) Horizon scanning of potential new alien vascular plant species and their climatic niche space across the Arctic . NeoBiota 104: 1-26. https://doi.org/10.3897/neobiota.104.165054
