Reindeer Grazing Cuts Shallow-Root Biomass in Finland’s Pine Forests

A new Finnish study has revealed that reindeer grazing substantially alters the below‑ground composition of northern pine forests, trimming the amount of shallow‑root biomass by almost a third compared with areas where the animals are excluded.

Researchers compared paired forest plots, some open to free‑ranging reindeer and others fenced off, measuring both the trees and the understory plants. The analysis showed that the grazed sites supported roughly 30% less shallow‑root mass, indicating that the animals’ foraging pressure reaches into the soil profile, not just the canopy.

The shift was not limited to a simple loss of root volume. The study documented a re‑organization of root architecture, with a relative increase in deeper roots as the shallow network was diminished. Such changes can affect how trees access water and nutrients, potentially influencing growth rates and resilience to environmental stressors.

Reindeer herding is a long‑standing practice across the boreal region, and the animals’ seasonal movements often bring them into forested areas that were traditionally considered wildlife habitat. As reindeer numbers have risen in parts of Finland, their grazing impact on understory vegetation has become more pronounced, raising concerns among ecologists about forest regeneration and biodiversity.

The findings carry weight for forest management and climate policy. Shallow roots play a key role in storing organic carbon close to the surface, where it is more vulnerable to decomposition and release as carbon dioxide. A reduction in this root pool could diminish the forest’s capacity to sequester carbon, complicating efforts to meet emission‑reduction targets.

Scientists say the results underscore the need for integrated land‑use strategies that balance traditional reindeer livelihoods with forest conservation goals. Ongoing monitoring of root dynamics, combined with adaptive grazing regimes, may help maintain both the cultural and ecological functions of these boreal landscapes.