When reindeer graze, forests breathe a little easier
Not all climate heroes wear capes. Some sport antlers. A four-year study conducted in Finland’s northern wilderness reveals that reindeer grazing can help stabilize the carbon stored in soil and understory plants beneath boreal forests. Published in Science of the Total Environment, the research shows that the herbivores’ foraging and trampling activities may buffer carbon release as snow conditions shift through winter.
The big question: how does grazing influence the carbon cycle?
Northern forests hold about a third of the planet’s terrestrial carbon, and while trees are the most visible carbon sinks, the soil and the low-growing understory plants that reindeer feed on play an equally important role. The University of Oulu team asked a simple but crucial question: how do reindeer grazing and snow depth interact to affect the carbon cycle during the growing season?
From 2019 to 2023, researchers carried out experiments in two contrasting Finnish sites: Oulanka in eastern Finland, where grazing has persisted for decades, and Kevo in the far north, where grazing has been excluded for 55 years. In both areas they manipulated snow depth to create patches of deeper and shallower snow. The goal was to observe how these changes influence carbon release when the snow thaws and summer soils warm up, a key period for carbon flux between soil and atmosphere.
Findings: grazing as a stabilizing force
In the long-term ungrazed area near Kevo (55 years without grazing), the depth of snow had a pronounced effect: shallower snow led to higher carbon release from the understory and soil, while deeper snow reduced release. In contrast, regions with ongoing grazing — including the 25-year site at Oulanka — showed stable carbon release regardless of snow depth changes. This suggests that grazing activity, along with the physical disturbance it causes, can dampen the sensitivity of the carbon cycle to winter climate variability.
Why does this buffering happen?
Lead author Noora Kantola explains that grazing alters the understory composition, which in turn moderates how warmth and moisture move through the soil. In the Kevo area, a recovery of lichen and other ground cover after decades without grazing may have transformed soil temperature and moisture dynamics. The team notes that changes in snow depth interact with the regenerated understory to influence soil decomposer activity, thereby affecting carbon emissions.
Implications for northern forests and climate resilience
The takeaway is nuanced but hopeful: allowing reindeer to graze and trampling vegetation — which shapes the understory and soil microclimate — can contribute to a more stable carbon balance in the short term. It does not imply that grazing is a universal fix for climate change, but it highlights a natural process by which herbivores can influence carbon dynamics in boreal ecosystems. These forests store vast amounts of carbon not just in living trees but in soils where microbial activity responds to snow and plant cover. If grazing maintains a steady carbon release rate, northern ecosystems may exhibit a degree of resilience to rapid winter climate shifts, at least in the near term.
What scientists want next
Researchers emphasize that long-term monitoring and expanded geographic scope are needed to fully understand the interaction between grazing, snow patterns, and soil carbon dynamics. As winter weather becomes increasingly erratic in a warming climate, such insights help refine carbon-budget models and improve predictions of how northern forests respond to environmental change.
A broader view: climate resilience across ecosystems
The Finnish study adds to a growing body of work that sees animals not merely as beneficiaries of ecosystems but as integral players in climate processes. From turtles linking to carbon sinks in unexpected places to herbivores shaping carbon release in boreal soils, these findings remind us that the climate system is a web of interdependencies where wildlife, snow, and soil all matter.
Top image: reindeer grazing. Credit: Noora Kantola / the University of Oulu
