Grazing Reindeer Could Help Cool the Planet

When they chew through vegetation, reindeer help dial back the amount of radiation absorbed by Earth.

Reindeer play a surprising role in easing climate change, reports a new study, by grazing on shrubs in the Arctic tundra.

A team of researchers report in the journal Environmental Research Letters that while feeding, wild reindeer herds in Norway boost the level of surface albedo - the amount of the sun's energy the Earth reflects back into space. Their munching reduces the height and number and shrubs to bring about the increase, said the scientists from Sweden's Umeå University.

In climate terms, higher albedo results in a cooling effect.

"Our theory was that heavy grazing by reindeer increases summer albedo, through a reduction in shrub height, abundance and leaf area index (LAI)," said the study's lead author, Mariska te Beest, in a statement. "The effect reindeer grazing can have on albedo and energy balances is potentially large enough to be regionally important. It also points towards herbivore management being a possible tool to combat future warming. Most of the arctic tundra is grazed by either domesticated or wild reindeer, so this is an important finding."

The scientists studied reindeer in summer months in Reisadalen, Norway, combining computer models of the landscape with field measurements of albedo and notations about the types of vegetation being grazed by the animals.

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"We found that high densities of reindeer changed arctic tundra vegetation by decreasing shrub abundance," said te Beest. "This resulted in corresponding shifts in LAI, canopy height and NDVI - the amount of live green vegetation."

The researchers found that the pronounced changes in vegetation resulted in increased albedo during the growing season. According to their computer models, the increase ultimately meant that the grazed sites absorbed less radiation.

"Our results show that reindeer have a potential cooling effect on climate, by changing the summer albedo," said te Beest. "Although the estimated differences might appear small, they are large enough to have consequences for the regional energy balance."

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