Climate change in Arctic regions is linked to an expansion of woody-taxa (shrubification) and an increase in biomass as tundra becomes greener. Herbivores like reindeer and caribou are often considered able to suppress this vegetative greening through trampling and grazing. Many studies have quantified the effect of herbivory on woody taxa in local experimental sites, but there are still few studies quantifying reindeer use at the landscape scale that can shed light on their potential to suppress Arctic vegetative greening.
This study has measured reindeer habitat use within the low Arctic tundra zone of Yamal, West Siberia using reindeer faecal pellet-group counts. Active layer thickness was also measured and related to the reindeer use, as intense use of for example denuded land also could favour deeper thawing of the permafrost. These measures can help us to understand herbivore impact on the growth and recruitment of deciduous shrubs, many of which serve as fodder (e.g. Salix spp.), in favourable habitats, such as naturally denuded landslides in permafrost areas.
The results confirm intensive use by reindeer of areas with higher productivity, low erect shrub tundra and upper slopes, ridges and valleys, while the use of tall Salix areas was less intense. This suggest that reindeer are unlikely to suppress growth of already tall-erect woody taxa, while they may suppress shrubs low in stature. The study did not find any direct relationship between permafrost thawing and reindeer use, but intensively used sites seemed to have a shallower active layer. The study concludes that reindeer use of the landscape and hence their effects on the landscape correlates with the landscape structure and that future research is needed to evaluate the role and efficiency of reindeer as ecosystem engineers capable of mediating the effects of climate change.
Reference: Skarin, A., Verdonen, M., Kumpula, T., Macias-Fauria, M., Alam, M., Kerby, J.T. and Forbes, B.C., 2020. Reindeer use of low Arctic tundra correlates with landscape structure. Environmental Research Letters.
https://doi.org/10.1088/1748-9326/abbf15
You can find the full paper here, and learn more about the study in the beautiful video summary below:
Picture: Reindeer in Yamal, Western Siberia (photo © Hannes Skarin).