Category: publications

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New paper on potential new alien plants across the Arctic

Invasive species are one of today’s main environmental challenges, implicated in biodiversity loss and causing huge ecological and economic costs. So far, the remote and cold Arctic tundra has been spared the worst impacts of invasive plants. However, increasing human activity and a warming climate together increase the chances for non-native plant introductions, and establishment. To facilitate monitoring and management of this challenge, NordBorN researchers including Kristine Westergaard and James Speed at the Norwegian University of Science and Technology, have carried out an horizon scan for potential non-native plants across the terrestrial Arctic. 

Starting with a list of globally invasive plants, they identified potential alien species as those with a climate overlap with today’s Arctic climate. They identified a total of 2554 new alien plant species that could potentially survive in the climatic conditions in the Arctic tundra. Some regions are identified as potential hotspots including western Alaska, southwestern and southeastern Greenland, northern Iceland, Fennoscandia, and Kanin–Pechora. The species that could potentially establish in the Arctic are widely distributed across the world. However, species with high latitude distributions (e.g. boreal species) had a higher likelihood and degree of climate overlap with the Arctic. The close geographical connection between the Arctic and boreal regions makes this area a key source for non-native species introductions to the Arctic. 

The number of potential new alien vascular plant species across the Arctic

The data-driven horizon scanning approach that is developed in this paper produces regionally-specific lists of risk species and source regions. These can help develop biosecurity, monitoring and rapid response measures, contributing to preserving the ecological integrity of the Arctic tundra into the future. 

Publication: Ulsted, T.H., Westergaard, K.B., Dawson, W., & Speed, J.D.M. (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

Photo: Alien Barbarea vulgaris growing on very disturbed substrates in Barentsburg, Svalbard. (Kristine Westergaard)

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Borealization of tundra plant communities is largely driven by species that are already in the Arctic

The composition of tundra plant communities is rapidly changing due to climate change. The potential encroachment of boreal species, from warmer, southern latitudes, is a conservation concern. Using the ITEX+ database, in a paper recently published in Ecology Letters Mariana García Criado and collaborators synthesized data from 32 study areas across the Arctic, including 287 vascular plant species and 1,137 plots, resurveyed between 1981 and 2023.

Conducting plant surveys in Kilpisjärvi, Finnish Lapland (photo credit; Jiri Subrt)

The aim of the study was to (i) quantify the borealization of tundra plant communities, (ii) assess the biogeographical, climatic and local drivers of borealization, and (iii) identify species contributing to borealization and their associated traits.

They found that around half of the surveyed plots experienced borealization, understood as the increase in occurrence and abundance of boreal species or species present on the boreal-tundra boundary. Borealization was greater in Eurasia, closer to the treeline, at higher elevations, in warmer and wetter regions, where climate change was limited, and where initial boreal abundance was lower. Boreal colonizer species were generally short-statured, and more often shrubs and graminoids.

The findings of this study indicate that tundra borealization is mainly driven by the spread of boreal-low Arctic tundra species, which are already present in tundra landscapes. These changes in plant community composition can have cascading impacts on land-atmosphere interactions, trophic dynamics and Indigenous and local livelihoods.

Reference: García Criado, M., Barrio, I.C., Speed, J.D.M., Bjorkman, A.D.,  Elmendorf, S.C., Myers-Smith, I.H., Aerts, R., Alatalo, J.M., Betway-May, K.R., Björk, R.G., Björkman, M.P.,  Blok, D., Cooper, E.J., Cornelissen, J.H.C., Gould, W.A., Gya, R., Henry, G.H.R., Hermanutz, L.,  Hollister, R.D., Jägerbrand, A.K., Jónsdóttir, I.S., Kaarlejärvi, E., Khitun, O., Lang, S.I.,  Macek, P.,  May, J.L., Michelsen, A., Normand, S., Olsen, S.L., Post, E., Rinnan, R.,  Schmidt, N.M., Sjogersten, S., Tolvanen, A., Töpper, J.P., Trant, A., Vandvik, V., Vowles, T. (2025) Borealisation of plant communities in the Arctic is driven by Boreal-Tundra species. Ecology Letters. https://doi.org/10.1111/ele.70209

The top picture shows a woolly willow (Salix lanata) growing in Latnjajaure, Sweden (credit Anne Bjorkman)

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Beavers and their ponds are moving north

The spread of the beaver (Castor canadensis) into the Arctic tundra is a textbook example of the process of borealization. A new study by Ken Tape at the University of Alaska Fairbanks and James Speed at the Norwegian University of Science and Technology and a member of the NordBorN network, shows how temperature is a crucial factor determining the distribution of beavers and their impact on the whole ecosystem through dam building across the Alaskan tundra.

Temperature drives an increase in suitable habitat for beavers from 15 000 km2 in the early 20th century, to 30 000 km2 at present, while future climatic warming is projected to increase the potential suitable habitat to between 100 000 and 150 000 km2 by 2090.

Such a dramatic increase in distribution of an ecosystem engineering species is likely to have dramatic impacts on the future state of the tundra.     

The paper was recently published in Environmental Research Letters, and has been featured in Science.

Reference: Tape, K. D., & Speed, J. D. (2025). Predicted expansion of beaver pond distribution in Arctic Alaska, 1910–2090. Environmental Research Letters, 20(9), 094009. 10.1088/1748-9326/adeba2

The picture shows a beaver modified habitat in Alaska (photo: Ken Tape, University of Alaska Fairbanks)