Antarctica is an icy place today, but the ice has expanded even further during past ice ages. Biologists have long wondered how and where life on land has survived on the icy continent over the centuries.
Ever since the first expeditions to Antarctica, the continued existence of life in this inhospitable environment has remained a mystery. Until now.
We collected data to test our theory of how life survived previous ice ages. We argue that life forms, including invertebrates, vertebrates, and plants, have subsisted by retreating to numerous ice-free areas called nunataks that were not buried by advancing glaciers.
Then, as Antarctica gradually warmed again, life spread from these nunatak refuges to repopulate larger ice-free areas. Our approach explains the uneven distribution of terrestrial life in Antarctica and identifies new research priorities to further test our theory.
The Coming Ice Age
With the Ice Age approaching, an unlikely trio of prehistoric creatures – Manny the woolly mammoth, Diego the saber-toothed tiger, and Sid the giant sloth – find an orphaned human child and decide to return it.
For many, the term “Ice Age” conjures up memories of the animated adventures of Manny, Sid, and Diego (and don’t forget Scrat the squirrel rat!) as they attempted to escape the advancing ice.
There may be some truth to this story. The idea of a mammoth, sloth, saber-toothed tiger (and pesky humans) migrating south to warmer climes is becoming more popular in the northern hemisphere. And research published this month suggests early humans survived the last ice age in the ice-free havens of southern Europe.
But in Antarctica, land-loving life forms had nowhere to go. At least that’s how it seemed until now.
As scientists began to learn more about life in Antarctica, they began considering the possibility of surviving in ice-free havens. But there was a problem. Any ice-free land in coastal regions where life exists today would certainly have been swallowed up by the expanding ice. So how did life survive?
Unusual ice-free havens
Using evidence from Antarctica’s biology and geology, we describe how ice-free havens (nunataks) could provide a respite for coastal species.
We have disregarded previous research that indicated that geothermal sites provide sufficient ice-free coastal havens. Because these would have been short-lived – compared to an ice age of around 100,000 years – and too few to explain the survival of life on the continent today.
We provide the first testable, evidence-based hypothesis for the existence of life on continental Antarctica in millions of years. And we did that with the most famous of all Antarctic invertebrates, a small creature that inhabits ice-free land year-round: springtails.
Springtails make an important contribution to soil health worldwide. They were among the first animals collected during early expeditions to the Antarctic Peninsula and the north coast of Victoria Land from 1897 to 1900.
We have compiled a database of Antarctic springtail distribution records from these initial discoveries more than a century ago to the present day.
We also looked at an existing resource that has not previously been used to explore these questions of survival. By examining the Informal Cosmogenic-nuclid Exposure-age Database (ICE-D) for Antarctica, we were able to show that ice-free conditions existed at a large number of locations during the last (and earlier) ice ages.
Cosmogenic nuclide dating is typically used to improve understanding of how ice sheets respond to climate change by revealing when a rock was last covered by ice. But it hasn’t been used to identify ice-free glacial sanctuaries.
We show that some of these ice-free havens existed over the expanding ice during past ice ages. Some included all species found in a region.
But how has life moved from these havens to recolonize habitats such as coastal areas? Evidence of this remarkable survival story comes from well-known alpine and polar studies showing that life in ice-free ecosystems near glacier margins shifts as the ice expands or contracts.
Learn life lessons
Life in Antarctica faces an uncertain future in the face of climate change. The region is witnessing more extreme events such as catastrophic ice shelf break-ups, the highest recorded air temperature in Antarctica, and the lowest sea ice on record. It seems like we are now living in the sequel Ice Age: The Meltdown. Let’s hope we’re doing as well as Manny and his friends.
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Antarctica will change forever, and limiting that change will require a collective “mammoth” effort on a global scale to rapidly reduce greenhouse gas emissions. This is a daunting and unprecedented challenge, but one that is needed to secure Antarctica’s future. Life Survived Ice Ages, But Can It Survive Us?
Mark Stevens, Adjunct Associate Professor, University of Adelaide and Andrew Mackintosh, Professor & Head, School of Earth Atmosphere and Environment; Expert on Glaciers and Ice Sheets, Monash University
This article was republished by The Conversation under a Creative Commons license. Read the original article.
also read | Antarctic sea ice coverage hits record low for second straight year: study
