A series of freezing rain in the Norwegian archipelago of Svalbard has led to an almost simultaneous decrease in the number of large herbivores to record low levels, indicating a very high vulnerability of arctic ecosystems to climate change and their accompanying weather events, according to an article published in the journal Science.
"We know that climate fluctuations can manage numbering several populations of the same species. This finding suggests that the climate and weather anomalies can cause simultaneous changes in entire ecosystems, which include several kinds of animals," — said the head group of ecologists Brahe Hansen (Brage Hansen) of the University of Science and Technology in Trondheim, Norway.
Hansen and his colleagues observed the state of the ecosystem on the island of Spitsbergen, situated far from the Arctic Circle, at 78 degrees north latitude.
As the scientists explain, the ecosystem of the archipelago is arranged very simply — it contains only three species of large herbivores — Svalbard reindeer (Rangifer tarandus platyrhynchus), tundra ptarmigan (Lagopus muta hyperborea) and voles (Microtus levis). The only inhabitants of Spitsbergen are predatory foxes (Vulpes lagopus), which are the basis of the diet rodents and birds, as well as the dead carcasses of deer.
All these herbivores feed on mosses and lichens growing on exposed areas of soil in summer and thick "coat" of snow in the spring. Occasionally in Svalbard are abnormal freezing rain, through which snow crusts of ice. These icy armor prevent deer scent vegetation, and do not allow voles and grouse access to food sources.
Group of environmentalists led by Hansen watched the fluctuations in the numbers of the four species in the last two decades, trying to assess how freezing rain effect on the ecosystem as a whole and of individual populations in particular.
It was found that the size of all three species of herbivores simultaneously increase or decrease depending on how often or rarely had freezing rain. As a rule, the long series of several rainy days extremely negative impact on the health of the ecosystem, causing a precipitous decline in the number of all the populations of grouse, voles and deer.
According to researchers, a similar plot of the number of foxes "delayed" for one year. Scientists explain that the predators can eat all year carcasses of deer, grouse and voles, which are virtually spoiled in a constantly low temperature on Svalbard.
Thus, Hansen and his colleagues have found out that the climate and extreme weather events can influence the state of the whole ecosystem, simultaneously increasing or decreasing the number of species. This fact, as well as the sharp fall in the number of animals that caused freezing rain, talk about the particular vulnerability of the Arctic to climate change, the scientists conclude.