Named after Vulcan, the Roman god of fire, volcanoes are best known for their destructive power.
But a new study bolsters the idea that they can also be havens for life, as refuges for plants and animals during ice ages.
Scientists have long wondered how diverse life-forms survived those periods of extreme cold and ice, the last of which peaked about 20,000 years ago.
In new research, Ceridwen Fraser of Australian National University and Aleks Terauds of the Australian Antarctic Division examined previously collected data on where plants, fungi, and invertebrates like mites live in Antarctica.
The scientists mapped the numbers of organisms in relation to geothermal areas—volcanoes, mostly—known to have been active since the last ice age. They found the number of species was greatest at or around such sites, which the scientists said reflected volcanoes' role as ice age refuges.
Particularly for plants such as mosses, the number of species steadily declined the farther away one got from geothermal areas.
To ensure that the decline in species richness reflected a historic trend, and not merely the preference of current species, Fraser's team considered sites "non-geothermal" only if they were over 62 miles (100 kilometers) from a geothermal site, far beyond the warming effect of a volcano.
"The heat from volcanoes is very localized—a kilometer or two away you won't feel it. If the diversity patterns were only linked to species preferring volcanic areas today, we'd only see more species right there on the volcanoes, and no gradient away from them," said Fraser.
Using diversity patterns to determine species distribution changes is an approach that's been well established in studies that focused on the Northern Hemisphere, said Fraser.
However, the new study, published March 10 in the Proceedings of the National Academy of Sciences, is the first to tackle the hypothesis that volcanoes provided safe havens for animals. The researchers looked at large sets of data for several species on a continental scale.
Fraser said the hypothesis could well extend to other parts of the world and other glacial periods the planet has experienced.
"Similar geothermal regions elsewhere, such as in the far north of the Northern Hemisphere, can also help explain the survival of some species at high latitudes through past ice ages," she said.
Ian Hogg, a biologist at the University of Waikato in New Zealand, said by email that "the hypothesis could help, at least partially, explain how life has managed to persist over millions of years within Antarctica."
Not as Barren as You Think
It's tempting to perceive Antarctica as a barren ice sheet interrupted by the occasional penguin, but in fact it's home to hundreds if not thousands of individual species—including 300 kinds of lichen—many of which require ice-free land to survive. (See "Antarctica May Contain 'Oasis of Life.'")
"It's likely that without such safe havens, the vast majority of Antarctic species would have gone extinct," said Fraser.
Unlike birds and marine life, which can move to warmer climes during glacial periods, plants, fungi, and invertebrates make excellent indicators for climate-related research because they are largely immobile, so their fate is more closely linked with their immediate environment.
The new mapping data suggest that species would have been concentrated around geothermal areas during glacial periods and then recolonized other territory during warming episodes. (See National Geographic's volcano pictures.)
Antarctica houses three major clusters of volcanoes—including the towering Mount Erebus. The volcanoes contain underground magma chambers, which can raise surface temperatures in areas near the crater.
Volcanoes also frequently emit steam, both from their craters and from ventlike openings called fumaroles, which can create ice-free areas known as "steam fields" and can hollow out large ice caves beneath glaciers. (See photos of the ice caves of Mount Erebus in National Geographic magazine.)
"In the subglacial caves ... temperatures can be tens of degrees Celsius higher than the outside temperature," said Fraser. "Open-air steam fields would also be relatively warm and moist—great for mosses and other species to thrive."
Antarctica was an ideal test case for the geothermal research because its isolation and ice cover make it less biologically "contaminated" by other species.
While they may not get the same attention as penguins and seals, animals like mites, springtails, and nematodes live in Antarctic hot spots.
"They're not as charismatic as these other animals," said Fraser, "but that's where most of the bioversity is."
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