Grazing Reindeer May Counter Some Climate Change Effects

Groups of hungry herbivores may be able to combat some of the effects of climate change in cold mountainous regions by eating up the plants that are beginning to grow outside of their typical growth zones.

One consequence of a warmer climate is that lowland plants migrate to higher elevations, but species such as reindeer, voles and hare are capitalizing on this effect of climate change and effectively preventing plant evasions, according to new research from Umeå University.

The study was part of the of the doctoral research of Elina Kaarlejärvi from the university's ecology department. She theorizes that a warming climate does not always result in increased plant biomass, invasions of new species and shrubification in tundra because native herbivores will eat their way through much of the new vegetation.

Her research challenges previously established positions on the topic. Earlier studies suggested that a warming climate will lead to increased shrub growth in tundra and that the shrubbery will grow taller, faster and take up more space.

"This shrubification together with new species migration to open tundra would increase competition among plant species and thus threaten the existence of low-stature tundra plants," Kaarlejärvi said. "My results from a field experiment in Abisko, in northern Sweden, indicate that reindeer grazing may protect the original tundra vegetation by keeping the vegetation low and preventing new species' invasions to the tundra."

Kaarlejärvi reports that reindeer are a key species that play an important role in balancing mountain vegetation.

"Changes in mountain vegetation depend on local reindeer numbers. Moderate grazing prevents new species upward shifts and reduces the growth of vegetation," she said. "Reindeer numbers vary significantly between different areas and different years. So we can expect more rapid changes due to climate warming in vegetation in the areas that are not grazed."