Could managing the grazing habits of a northern species help cool the planet?
Creative scientists and engineers have come up with a long list of ways to mitigate future warming of the planet. Some of the schemes are outlandish, others are controversial, and some are planetary-scale mega-projects. Some, however, are low-tech and small-scale, and could have a place in a global network of regionally important strategies.
Anthropocene recently reported on one such simple concept. Landscape engineering of the four-hoofed kind, based on research conducted by ecologists at Sweden’s Umeå University.
Previous studies have shown that shrub cover is increasing at high latitudes in response to climate change. The change in vegetation type has led to a decrease in surface ‘albedo,’ the reflection of light back from the Earth’s surface. Less reflection means more energy is absorbed, heating the surface and leading to an increase in warming in a positive feedback loop. (This is the same process whereby less Arctic ice increases the amount of energy absorbed in polar oceans and increases ocean warming.)
Reindeer (aka caribou in North America) are herbivores—they eat only plants. Herbivory is known to control vegetation height and abundance, so the scientists combined field measurements of albedo, herbivory, and vegetation characteristics with land surface modeling to investigate if reindeer grazing could influence the energy balance of an Arctic tundra.
The research team conducted their study in northern Norway. They isolated plots along a reindeer fence that was built in the 1960's to help the Sámi people keep their reindeer herds within their legal summer ranges. The fence dissected several vegetation types, and the research plots permitted different grazing intensities.
Results of the study were recently published in Environmental Research Letters. Their findings showed that when reindeer reduced shrub height and abundance, more reflective grass species often grew in their place, and summer albedo increased in several vegetation communities.
The researchers wrote that reindeer have “a potential cooling effect on climate by increasing summer albedo,” and that “the estimated differences might appear small, but are large enough to have consequences for the regional energy balance.” They further suggested that herbivore management could be a potential tool to mitigate future warming “since most of the Arctic tundra is grazed by domesticated or wild reindeer.”
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The scientists also noted that the strong effects of reindeer on albedo are probably restricted to areas with high reindeer densities, “since a dramatic vegetation change is essential.”
Unfortunately, high reindeer densities may not be guaranteed in the coming years. According to the International Union for Conservation of Nature (IUCN), the world’s caribou and reindeer are classified as a single species, and the species as a whole has suffered a decline of up to 40 percent in the past 10-25 years. It was red-listed in 2016 as “Vulnerable.”