Study reveals crowberry expansion and bilberry decline in Arctic tundra
image:
Crowberry is taking over the fells, where it has conquered areas covered by bilberry and heather vegetation types, as well as open, wind-swept areas. These changes are affecting the sensitive ecosystems of the fells. Photo: Tuija Maliniemi, University of Oulu
view moreCredit: Photo: Tuija Maliniemi, University of Oulu
Researchers at the University of Oulu, Finland have observed significant vegetation changes in the treeless heath and tundra regions of northern Finland and Norway over recent decades, marked by the expansion of crowberry (Empetrum nigrum) and the decline of bilberry (Vaccinium myrtillus).
A new study indicates that the primary vegetation types in these areas—bilberry, crowberry, dwarf birch, and heather -dominated tundra—are becoming increasingly homogenized. This shift is particularly evident in bilberry-dominated landscapes, where crowberry proliferation coincides with bilberry decline. While bilberry remains a dominant species, its reduction could impact local ecosystems and alter the visual landscape, especially during autumn foliage.
The research, covering areas from Riisitunturi in northern Finland to Finnmark in Norway, utilized long-term data sets, a rarity in vegetation studies that often focus on shorter time frames and smaller regions. "Over the past decade, we've re-surveyed tundra heathlands initially mapped by Matti Haapasaari in the 1960s and 1970s. Such meticulously collected historical data are invaluable for detecting long-term vegetation changes. We plan to continue monitoring these areas in the future," says Academy Research Fellow Tuija Maliniemi.
The greening of the Arctic region also affects Lapland
Arctic regions are experiencing rapid warming, leading to increased greening and shrub expansion. However, in Finnish Lapland and northern Norway, this trend is decelerated by extensive reindeer grazing, which suppresses the growth of mountain birch and other taller shrubs. Consequently, the greening manifests as the spread of dwarf shrubs, notably crowberry.
The decline of bilberry, which is not expanding into new areas, raises concerns among researchers. "The reasons behind bilberry's decline have not been extensively studied. The unique and locally variable nature of tundra ecosystems suggests multiple factors, such as changes in snow conditions, the proliferation of evergreen plants, and reindeer grazing, may be contributing," notes Doctoral Researcher Petteri Kiilunen from the University of Oulu.
The study Long-term homogenization of Fennoscandian heathland and tundra vegetation is connected to the expansion of an allelopathic dwarf shrub was published in the Ecography scientific journal on October 10th, 2025.
Learn more
- Climate change and forest management can threaten blueberry microbes – differences between northern and southern blueberries
- Researchers discuss the blueberry situation in a video
- Reindeer grazing can mitigate the impacts of winter climate change on forest carbon release
- Physical Geography Research Group at the University of Oulu
Article Title
Long-term homogenization of Fennoscandian heathland and tundra vegetation is connected to the expansion of an allelopathic dwarf shrub
Article Publication Date
10-Oct-2025
Instagram photos help scientists track invasive plant flowering patterns
Invasive succulent that smothers native plants shows extended flowering in new territories, where it can dominate coastlines
University of Galway
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Carpobrotus invasion at Duna do Caldeirão, Vila Praia de Âncora, Portugal. Credit: Jonatan RodrÃguez, University of Santiago de Compostela.
view moreCredit: Credit: Jonatan RodrÃguez, University of Santiago de Compostela.
That vibrant carpet of pink and yellow flowers blanketing Mediterranean cliffs might look beautiful in holiday photos on a social media feed. But scientists have discovered these same Instagram snapshots are revealing how one of the world's most destructive coastal plants is taking over new environments by extending its flowering season and threatening native biodiversity.
An international team of researchers analysed more than 1,700 photographs from social media and citizen science platforms to track Carpobrotus species - commonly known as ice plants or sour fig – across South Africa, Argentina, New Zealand, Portugal, Spain and the US.
These fleshy evergeen succulent plants are native to South Africa but now smother coastal ecosystems from California to the Mediterranean and transform ecosystems.
A single Carpobrotus plant can cover up to 50m², suffocating everything beneath it. They change soil chemistry and monopolise pollinators with their showy flowers, disrupting local ecosystems.
The findings have been published in Ecological Solutions and Evidence.
They are the result of a global study conducted by University of Galway, Institute of Botany of the Czech Academy of Sciences, University of Santiago de Compostela in Spain, Experimental Station of Arid Zones in Spain, Charles University in the Czech Republic, Macquarie University in Sydney, Stellenbosch University in South Africa, and Penn State University.
Dr Susan Canavan, lead author and Honorary Researcher with the College of Science and Engineering at University of Galway, said: "We realised thousands of people were unknowingly documenting these invasions in the background of their beach selfies and cliff-top sunset photos. This gave us observers across the globe, from California's Big Sur to New Zealand's coastlines to Portugal's tourist beaches.”
For the research team, California's tourist hotspots provided nearly three times more usable photos than other regions, while remote locations in South Africa and the Azores relied entirely on dedicated naturalist platforms like iNaturalist.
The team discovered that the Carpobrotus populations flower longer than native ones, potentially producing more seeds and increasing their spread. In their native South Africa, the plants show a short, concentrated flowering peak but in invaded regions, they bloom across extended periods. This reproductive advantage may help to explain their invasive success.
They also found that local environmental conditions override genetic differences in determining flowering timing. The plants adapt to bloom during the local spring season, such as October in New Zealand and May-June in California and Europe, rather than maintaining the flowering patterns from their native range.
For coastal managers battling these invaders, the findings offer practical guidance - by revealing peak flowering times in the invaded regions, the research will help them to time removal efforts to prevent seed production.
Dr Canavan added: "Tourist destinations were goldmines of data. Every scenic overlook with Carpobrotus had hundreds of Instagram posts. But this also showed us the bias in social media data. Remote invaded areas remain invisible without citizen scientists actively documenting them.
“The study also demonstrates how the digital age is transforming ecological research. What began as vacation photos and nature observations has become a powerful tool for tracking biological invasions.”
Dr Ana Novoa, co-author and project lead from the Institute of Botany of the Czech Academy of Sciences, said: "These plants are notoriously difficult to control because they spread both by seed and by fragments. Even a small piece can regrow into a new colony. Knowing exactly when they flower in each region means we can strike when they're most vulnerable, before they produce the thousands of seeds that ensure next subsequent invasions."
Open flower and a bud of Carpobrotus in the Tower of Hércules Natural Reserve, A Coruña, Spain.
Carpobrotus plants competing for space and pollinators with the native gorse Ulex europaeus in the Tower of Hércules Natural Reserve, A Coruña, Spain.
Credit
Jonatan RodrÃguez, University of Santiago de Compostela.
The full study, published in Ecological Solutions and Evidence, is available at https://doi.org/10.1002/2688-8319.70122.
Ends
Journal
Ecological Solutions and Evidence
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
iEcology reveals the importance of geography and genetic makeup in the flowering phenology of invasive Carpobrotus taxa
Article Publication Date
13-Oct-2025
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