Global Warming Threatens Lemmings in Norway

Kate Ravilious
for National Geographic News
November 5, 2008

Climate change may be responsible for shrinking lemming populations in Norway, a new study shows.

As a result, the lack of the small mammals is cascading through the ecosystem, forcing predators to find different food sources.

Lemming populations throughout Scandinavia tend to explode naturally every three to five years, causing huge numbers to go in search of food.

Occasionally this leads the rodents to jump into water and swim to new pastures—the origin of the myth that lemmings commit mass suicide.

When lemmings boom, they're hard to miss. Norwegians have had to use snowplows to clear the squashed rodents off the roads.

In recent years, however, outbreaks have become a rarity in many parts of Scandinavia.

The Wrong Kind of Snow

Kyrre Kausrud, a professor at the University of Oslo in Norway, and his colleagues analyzed lemming boom-bust cycles since 1970 for one site in southern Norway. Their findings are reported tomorrow in the journal Nature.

The data revealed that lemmings in this region have not had a population explosion since 1994.

Climate data collected over the same period suggest that warmer temperatures can explain why the rodents' numbers have remained low for more than a decade.

(Read more about global warming.)

During the winter lemmings live in tunnels under the snow. Warmth from the Earth melts some of the snow near the ground, providing pockets of air and access to food such as moss.

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