Tuesday, 22 January 2013

Climate Events Drive High-Arctic Vertebrate Community Into Synchrony: Extreme Weather Potent Force for Arctic Overwintering Populations

Jan. 17, 2013 — Climate change is known to affect the population dynamics of single species, such as reindeer or caribou, but the effect of climate at the community level has been much more difficult to document. Now, a group of Norwegian scientists has found that extreme climate events cause synchronized population fluctuations among all vertebrate species in a relatively simple high arctic community. These findings may be a bellwether of the radical changes in ecosystem stability that could result from anticipated future increases in extreme events.

The findings are published in the 18 January issue of Science.

The Norwegian scientists, with lead authors from the Centre for Conservation Biology at the Norwegian University of Science and Technology (NTNU), wanted to know how climate and weather events influenced an overwintering vertebrate community on the high arctic island of Spitsbergen, Svalbard, at 78 degrees N latitude.

They chose this simple ecosystem because it is composed of just three herbivores in the winter -- the wild Svalbard reindeer (Rangifer tarandus platyrhynchus), the Svalbard rock ptarmigan (Lagopus muta hyperborea), and the sibling vole (Microtus levis), and one shared consumer, the arctic fox (Vulpes lagopus).

The community's population fluctuations were mainly driven by rain-on-snow events, the researchers found. Rain-on-snow is an extreme climatic occurrence that causes icing on the deep-frozen arctic tundra. The ice keeps reindeer from grazing on their winter pastures and also reduces food accessibility for the rock ptarmigan and sibling vole populations, causing extensive simultaneous population crashes in all three species in the winter and spring after the extreme weather.

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