What Introduction of large herbivores in ecosystems where they are currently extirpated is a way of restoring natural ecosystem dynamics. Large animals effectively increase the landscape variation and in turn biodiversity. However, how large animals influence other ecosystem functions, such as carbon storage, is not well understood. Dragging carbon out of the atmosphere and into biomass in vegetation and soils is often highlighted as a promising strategy for reducing climate warming. However, in Arctic tundra carbon is currently being released to the atmosphere, particularly due to warmer soils. HERBIVARC studies the potential of large herbivores to decelerate this release of C from soils to the atmosphere by stabilising the carbon in the soil. Why Over the last few decades, our knowledge about Arctic ecosystem responses to climate warming has increased exponentially. Yet, the role of large herbivores in regulating interactions between vegetation and soils and the combined impact on climate feedbacks remains poorly explored. Soils are important global carbon (C) stores, and as the Arctic region warms about 4 times faster than the global average, the Arctic soil C-pool is currently being released to the atmosphere as greenhouse gasses. Introduction of large herbivores may have the ability to decelerate this trend, partly through increasing the soil C-input and -stabilisation. HERBIVARC will elucidate changes in soil C-dynamics caused by herbivore introduction in the tundra and estimate its potential for climate change mitigation. How In 1996, an assembly of large herbivores including bison, yakutian horses and reindeer were introduced into an area called the Pleistocene Park (PP) in Northeastern Siberia. This experiment has created a unique opportunity to study the effects of herbivores on ecosystem dynamics on timescales relevant for climate change. In HERBIVARC, we will combine field-based estimates of greenhouse gas effluxes from soils inside and outside the PP. Moreover, we will take soil samples for studying soil C-mobilisation and -stabilisation under laboratory conditions. We will explore the potential biological drivers of the changes soil C dynamics by quantifying the changes in soil faunal and microbial communities associated with large herbivore introduction. SSR HERBIVARC will shed light on the promises of large herbivore introduction in the Arctic as a strategy for decelerating climate warming. Rewilding and ecosystem restoration is by both the UN and EU deemed one of the most promising techniques for contributing to solving both the biodiversity and climate crisis at the same time. While the positive effects on biodiversity seems unequivocal, the acclaimed climate mitigation potential is yet to be confirmed by scientific evaluations. HERBIVARC will provide important new knowledge about this aspect of one of the most debated restoration techniques. If introduction of large herbivores proves effective for reducing soil C-loss, rewilding may be considered a natural climate solution, which is not only relevant in the vulnerable Arctic landscape, but across the world were rewilding projects are increasing dramatically in abundance.