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Arctic predator faces migration or death

January 18, 2013 in Science

EMBARGOED till 2200 GMT on Friday 18 January

By Tim Radford

There will be winners and losers among Arctic creatures trying to survive intensified climate change, which is already leaving its mark on some plants found far further south.

LONDON, 18 January – Climate change, with associated extremes of cold, rain and warmth, could make life very tricky for some of the Arctic’s most charismatic animals.

Those with somewhere to go could survive migration to more suitable climates, according to new research in three journals. But those that depend on others for their daily supper could find periodic difficulties. Spring already arrives earlier and flowers are blooming at unprecedented dates, but one or two rare blooms may be extinguished altogether.

Conservation biologists at the Norwegian University of Science and Technology report in Science that they examined the dynamics of a simple ecosystem on the island of Spitsbergen in the Svalbard archipelago, at 78 degrees North latitude.

The components were the wild Svalbard reindeer, a bird called the Svalbard rock ptarmigan, a European rodent called the sibling vole – and a predator, the Arctic fox. What caused population fluctuations, they found, were simple events: rain on snow, followed by extreme cold.

Arctic fox

Arctic foxes in Svalbard will have more than enough food during rainy and icy winters because there will be many reindeer carcasses for them to eat. The next winter, however, the fox population size will be reduced because a robust and small reindeer population will mean many fewer deaths and hence, very little carrion. Image: Brage B. Hansen, NTNU Centre for Conservation Biology

The snow cover would freeze, preventing the reindeer, the ptarmigan and the vole from grubbing for food beneath the snow.  Many would die, populations would crash.

However, the Arctic fox – perfectly happy to eat carrion – would do very well on dead reindeer carcasses and flourish. But the following winter, reindeer would be scarce, birds and voles difficult to find and the foxes would starve, one year out of step.

Rain on snow, followed by ice, is rare in much of the Arctic, but Svalbard has an oceanic climate: such events could be more common as the high Arctic warms with climate change.

Ice on top of snow can damage vegetation and reduce the richness of life in the soil. The Norwegian team think that damage to a community forced to overwinter could cascade through the food web.

“The die-offs among resident herbivores shape predator abundance, which could in turn affect the migratory prey that reside in the area in the summer, such as sea birds and barnacle geese,” says Brage Bremset Hansen, lead author of the paper.

But some creatures will cope with change, according to ecologists at Umeå University in Sweden. They modelled the distribution of species in northern Europe’s Arctic and sub-arctic land areas and predicted that the climate change expected by 2080 could benefit most mammals – with the exception of the lemming and the Arctic fox, both cold climate specialists.

“…even well-protected and even relatively abundant species may succumb to climate-induced stresses.”

But the “winners” would survive only if they could safely move to new ranges with climates to which they were adapted. “It is highly improbable that all mammals will be able to do so, owing partly to the increased fragmentation of their living environment caused by human beings,” said Christer Nilsson, one of the authors, in PLoS ONE (the Public Library of Science One).

One creature with nowhere to go as the world warms could be a rare flowering plant called the Haleakalā silversword, which makes its home high on just one Hawaiian volcanic crater.

It grows for between 20 and 90 years before flowering, just once, at the end of its life. Its survival was first endangered by humans who picked the flowers, and by introduced grazing animals: protection arrangements were introduced and the population recovered but, scientists warn in Global Change Biology, it could succumb to global warming.

“The silversword example foreshadows trouble for biodiversity in other biological hotspots,” said Paul Krushelnycky of the University of Hawaii, “and it illustrates how even well-protected and even relatively abundant species may succumb to climate-induced stresses.”

But there is more benign news from the eastern United States where, on average, spring blossoms appear 11 days earlier than they did when the great American writer and naturalist, Henry David Thoreau, began keeping records at Walden Pond, near Concord, Massachusetts 161 years ago.

And a thousand miles away in Wisconsin, in 2012 and during the warmest spring on record, plants bloomed on average a month earlier than 67 years ago, when the pioneer conservationist Aldo Leopold began keeping notes, researchers report in PLoS ONE. The research has important implications for predicting plant responses to climate change. – Climate News Network

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