Photo credit: Åshild Ønvik Pedersen, Norwegian Polar Institute
Against the odds
Why some Svalbard reindeer are thriving despite climate change
Svalbard reindeer live at the top of the Earth in one of the most rapidly changing Arctic environments. As ÅSHILD ØNVIK PEDERSEN writes, this cold-adapted, endemic species inhabits almost all vegetated areas of the archipelago—and unlike populations elsewhere in the Arctic that have seen declines, their numbers doubled from the 1980s to 2015 (the last survey date). But some Svalbard populations have declined or remained stable in size while others have grown more than threefold. What’s going on?
To answer that question, scientists are turning to one of the longest-running wildlife studies in the Arctic, covering nearly 50 years of data. Researchers with the Climate-Ecological Observatory for Arctic Tundra (COAT) have been tracking Svalbard reindeer by counting them, noting their age and sex. They are also marking and recapturing individual animals to follow their survival, reproduction and movement over time. These long time-series allows scientists to link reindeer health and numbers directly to shifts in weather and climate.
COAT: Norway’s Arctic early-warning system
The Climate-ecological Observatory for Arctic Tundra (COAT) is a Norwegian program that tracks the effects of rapid climate change in the far north. COAT uses extensive fieldwork, satellite and drone imagery, weather stations, and automated sound and photo monitoring to document shifts across entire ecosystems—from plants to predators. Reindeer are a key focus: COAT researchers track population trends, forage quantity and quality, and the cascading effects of climate warming on reindeer health and survival. This work helps explain how changing snow and vegetation conditions influence reindeer movements and the wider tundra food web.
Since 2010, COAT has grown into an international research hub, contributing data to nearly 300 publications, including Arctic Council reports. By revealing how ecosystems are transforming, COAT aims to equip Norway and the global community with the knowledge needed to manage and adapt to the climate crisis.
Svalbard reindeer live on the northern edge of the species’ range. Like their relatives elsewhere, they shape the tundra by grazing, fertilizing and trampling vegetation. They are also an important part of the Arctic tundra food web: when they die, scavengers like the Arctic fox rely on them for food.
But while the Svalbard reindeer are all part of a single subspecies, their fortunes differ according to whether they dwell mainly in the archipelago’s coastal or inland areas.
Winners and losers in a changing climate
Climate change has brought both benefits and challenges to these reindeer: icing episodes caused by winter rain can trap plants beneath ice, making it hard to get enough food. On the other hand, longer snow-free seasons give them more time to feed and store energy before winter. The body mass of females is crucial for reproduction and survival and explains nearly 90 percent of the variation in population size from year to year. Body mass variations are connected to winter conditions, reproduction and competition among reindeer for food when population densities are high.
When rainy winters create icy pastures, locking plants beneath a frozen basal ice layer, starvation can result in mortality, especially among the youngest and oldest reindeer. Few calves are born the following summer, leading to population declines.
These icing episodes can cover large areas of land. But the combined effects of these events and changes in summer conditions lead to different outcomes in our two core monitoring areas, home to coastal and continental reindeer populations. The explanation likely lies in small but important differences in weather, climate and how the reindeer themselves respond.
Photo credit: Tore Nordstad, Norwegian Polar Institute
Same islands, different experiences
At the meteorological station in Ny-Ålesund, on the west coast of Spitsbergen, the largest island of the Svalbard archipelago, the annual amount of winter rain has been considerably greater than at the Svalbard Airport station in central Spitsbergen. This has caused more severe icing events and harsher conditions for coastal reindeer. But inland, warmer summer temperatures have promoted plant growth, partly offsetting the negative effects of winter rain. As a result, population trends have diverged: while reindeer numbers have not increased on the coast, they have grown more than threefold in central Spitsbergen.
Rapid climate change effects and reindeer responses are revealing uncertainties and new concerns about how this cold-adapted species will cope as the pace of change accelerates.
– Åshild Ønvik Pedersen, Arctic ecologist and Senior Researcher
The COAT observatory shows that even within a single Arctic archipelago—in this case, Svalbard—climate change can shape populations in very different ways, with local weather patterns tipping the balance between growth and decline. Put simply, in inland Spitsbergen, the positive effects of summer warming have outweighed the negative effects of winter warming, leading to a steep rise in population size, while on the west coast, the opposite appears to be the case.
Rapid climate change effects and reindeer responses are revealing uncertainties and new concerns about how this cold-adapted species will cope as the pace of change accelerates. The big question is whether Svalbard’s reindeer—and other Arctic wildlife—can keep adapting to a climate that is reshaping their world so quickly.
