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Lichen Decline Was Weaker on Winter Reindeer Pastures in Northern Finland

Four reindeer, including a calf, on a low-shrub-covered hillside in Finnish Lapland
Research · Ecology

Lichen cover declined less on winter ranges used by reindeer (Rangifer tarandus) than on summer and year-round ranges in northern Finland, according to a study published in March 2026. The study concerned semi-domestic reindeer grazing freely on natural pastures in the 20 northernmost reindeer-herding districts.

Researchers compared vegetation at 617 field sites surveyed in 2005–2008 and again in 2016–2018. Dwarf-shrub cover and height increased overall, while lichen cover declined. Their models also indicated different changes in lichen height: an increase on winter ranges, but a decrease on summer and year-round ranges.

Model estimates of changes in lichen and dwarf-shrub cover and height under winter, summer and year-round reindeer grazing
Model estimates of changes in lichen cover, dwarf-shrub cover, lichen height and dwarf-shrub height. Blue curves represent winter ranges, green curves summer ranges and yellow curves year-round ranges. The dashed vertical lines mark no change. Figure 2 from Stark et al. (2026), CC BY 4.0; extracted from the published page without changing the figure.

Higher reindeer density was linked to stronger lichen decline

Higher reindeer densities were associated with more negative changes in lichen cover and height on both summer and winter ranges, but not on year-round ranges. The models indicated increasing shrub cover on summer and year-round ranges, while the expected change on winter ranges was close to zero or slightly negative. Higher reindeer density was also associated with a smaller increase in shrub height on winter ranges.

Plant interactions also shaped lichen change

Plant interactions also mattered. Lichen cover declined more where dwarf-shrub cover increased, but lichen height tended to increase where shrubs grew taller. The authors interpret this as a dual relationship: shrubs can compete with lichens for space and light, while taller vegetation may also create a more favourable microclimate or partly shelter lichens from grazing. They also note that snow cover can buffer lichens from trampling on winter ranges, whereas exposed lichens can be more vulnerable during dry summer conditions.

The authors argue that seasonal rotation between summer and winter ranges may become increasingly important for maintaining lichen pastures as the climate warms.

Sources and image credit

  1. Stark, S., Wallén, H., Kurkilahti, M., Pekkarinen, A.-J., & Kumpula, J. (2026). Plant interactions, climate, and the reindeer (Rangifer tarandus) interdependently shape vegetation in northern Finland. Ecological Applications, 36(2), e70200. https://doi.org/10.1002/eap.70200Primary open-access research article first published 10 March 2026 under CC BY 4.0. Vegetation at 617 field sites in the 20 northernmost reindeer-herding districts of Finland was compared between 2005–2008 and 2016–2018. Dwarf-shrub cover and height increased overall while lichen cover declined. Lichen cover declined less on winter ranges than on summer and year-round ranges; lichen height increased on winter ranges but declined on summer and year-round ranges. Higher reindeer densities were associated with lower lichen cover and height.

Image: Simo Räsänen / Wikimedia Commons — reindeer on Saana, Enontekiö, Finnish Lapland, 4 August 2026. Representative photograph of natural pasture; not identified study animals. · CC BY-SA 4.0 · Source

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