Rudolph is known for being helpful, but it turns out he may be more useful than anyone ever realized.
According to a study published in the journal Environmental Research Letters, scientists found that grazing reindeer cause the amount of sunlight reflected into space — called albedo — to increase.
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That's a good thing. As temperatures rise in Arctic regions, ice melt. That ice is needed to reflect some of the sun's radiation back into space. With less ice, there's less surface area to reflect that radiation. Instead, open water — which has a low albedo — absorbs the radiation, causing further warming.
In the case of the tundra, studies have shown that warmer climates cause vegetation to thrive, lowering the albedo and also contributing to local warming. But when the reindeer graze, it lowers that vegetation. In particular, areas with dense reindeer populations.
"Our results show that reindeer have a potential cooling effect on climate, by changing the summer albedo," Mariska te Beest, from Umeå University in Sweden and lead author of the study, said in a statement.
"Although the estimated differences might appear small, they are large enough to have consequences for the regional energy balance."
Researchers studied the reindeer during summer in the Troms, Norway. There they measured soil moisture, temperature, vegetation and even collected dung samples.
Though their results suggest reindeer grazing can reflect more sunlight into space, it did come with a climate change downside: increasing soil temperature.
Soil is an effective carbon sink, sucking up carbon dioxide. It's estimated that soil around the world stores billions of tonnes of carbon.
In the case of the grazing, the disrupted and exposed soil acts as a weaker carbon sink.
"Although grazing might be beneficial in terms of decreasing the net radiation, it might not be in term of releasing carbon into the atmosphere," the authors wrote in the study.