Norway: Climate Change, Snowpack, and Lemmings

Wed Nov 5, 2008 1:36pm EST

Lemmings in Norway hit by global warming: study
By Alister Doyle, Environment Correspondent

OSLO (Reuters)-Lemming numbers are dwindling in
Norway because of climate change, ending a
historic cycle of population booms and busts that
inspired a myth of mass suicides by the rodents,
scientists said on Wednesday.

Fewer lemmings-small brown, black or yellowish
mammals-in the mountains of south Norway meant
predators such as the Arctic fox were forced to
eat other prey including grouse and ptarmigan

“The lemming population is falling and the peaks
are disappearing,” said Nils Stenseth of Oslo
University, one of the authors of the report
published in the journal Nature and written with
colleagues in Norway and France.

He told Reuters it was the first study to link
lemming numbers and disruptions to snowfall
caused by global warming. The study of lemmings
since 1970 showed the last population boom was in
1994, ending a pattern of spikes every 3-5 years.

Female lemmings can have litters of up to 12
young three times a year and the population can
rocket if they are able to live sheltered from
predators in early spring in gaps between powdery
snow and the ground where they eat moss and other

But warmer temperatures in recent years meant
snow was wetter, often turning hard and icy. That
made it more difficult for rodents to hide and
reach food.

“A relatively small effect on one particular
species is having a broad effect on the system,”
Stenseth said. In years with a lemming population
boom, predators such as Arctic foxes or snowy
owls used to get a valuable boost.


“Now when the lemming peak is gone…they will
prey on other species such as ptarmigan and
grouse,” he said.

Tim Coulson of Imperial College, London, wrote in
Nature in a commentary on the study that lemmings
were so common in north Norway in 1970 that
“snowploughs were used to clear the vast numbers
of squashed animals from roads.”

But population surges quickly led to food
shortages and mass migrations. “On occasion,
desperate to find food, they jump into water and
start swimming. This behavior led to the myth
that lemmings commit suicide,” he wrote.

Lemmings are, however, still abundant. “We are a
long way from it being a threatened species,”
Stenseth said. Temperatures in late winter and
early spring in southeastern Norway in recent
decades were the highest since records began in

The U.N. Climate Panel projects that temperatures
will keep rising, bringing more droughts, floods
and heatwaves. Man-made emissions of greenhouse
gases, mainly from burning fossil fuels, are the
main cause, it says.

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