A long-running Kilpisjärvi experiment found that reindeer grazing changes flower and insect relationships on the fells more than added nutrients do.
Fell meadows fenced off from grazing drew more pollinators than grazed ones, and the effect was strongest on the barren tundra, a University of Oulu study reports.
Reindeer grazing changes the relationship between flowers and insects on the fells of Lapland more than added nutrients do, according to a study by the University of Oulu reported on 17.9.2026. The effects were strongest on barren tundra, and the fell meadows that drew the most insects were those fenced off from grazing.
A fence, added nutrients and two fell meadows
The flower visitors were counted on two experimental areas near Kilpisjärvi. One lies above the treeline on barren tundra, the other on a more fertile meadow in the mountain birch zone. At each site 16 plots were either left open to reindeer or fenced off, with or without added nutrients. The treatments were set up in 2014–2015 and the insects were watched in July 2022. The work is part of the international Nutrient Network experiment.
Flower visits on the two sides of the fence
On the tundra the highest count came from plots that were both fenced and fertilised; on the mountain birch meadow, from the fenced plots. Counts from the research paper.
Keeping reindeer out was the single factor that mattered most. Fencing raised the number of pollinators and other flower-visiting insects, the richness of insect families and the number of visits to plants. The effects were stronger on the barren tundra meadow than on the more fertile meadow among the birches. Many arctic plants depend on insect pollination, notes Risto Virtanen, senior curator at the University of Oulu.
Insect numbers and the richness of insect families rose as the number of flowers rose. A larger number of flowering species did not lift insect numbers in the same way.
“The results suggest that in northern environments the abundance of flowers may matter more to insects than the number of flowering plant species,” says Nicolina Johanson, a doctoral researcher at the University of Oulu.
Grazing bites hardest soon after the snow melts, when reindeer eat the flower stems as they develop. That is why the difference shows on the ground: where reindeer have grazed there are fewer flowers open, and fewer insects on them. Along a fence line the two sides can look like two different meadows.
The reindeer is the animal that shapes the Lapland landscape most. What else lives on the fells is in our wildlife guide.
Finland's new reindeer husbandry act requires planning for the sustainable use of reindeer pastures. The researchers note that where and when grazing happens, such as rotational grazing or grazing later in the season, may be important for pollination.
“The timing decides how many flowers, and what kinds of flowers, the fells offer insects,” Virtanen says.
The study was published in the journal Global Change Biology in August 2026. It is open access, so the full paper can be read without a subscription.