November 12, 2017
Ancient Antarctic Forests Offer Look At Plant Life Prior To Permian-Triassic Mass Extinction Event

Long before the continent was known for its frigid weather and ice sheets, Antarctica was a land of green forests. And while there wasn't much known about how life in Antarctica was in those prehistoric times, a team of scientists was able to find several prehistoric fossils in the area, revealing that the continent's trees might have grown about 260 million years ago, toward the end of the Permian era.

Immediately preceding the Triassic era and the rise of the first dinosaurs, the Permian era ended about 251 million years ago, with a mass extinction event that killed off about 90 percent of life on Earth, including Antarctica's polar forests. As noted by the International Business Times, previous research has suggested that the Permian-Triassic mass extinction took place due to a significant change in our planet's climate brought about by an increase in atmospheric greenhouse gases.

In an attempt to learn more about Antarctica's greener, less frigid past, geologists Erik Gulbranson and John Isbell, both from the University of Wisconsin-Milwaukee, traveled to the continent, climbing the slopes of the McIntyre Promontory in the Transatlantic Mountains and searching for forest fossils. Over a two-month period from late November 2016 through January of this year, the scientists found fossils belonging to 13 trees, concluding that they might have grown over 260 million years ago, wrote.

"People have known about the fossils in Antarctica since the 1910-12 Robert Falcon Scott expedition," said Gulbranson in a statement.

"However, most of Antarctica is still unexplored. Sometimes, you might be the first person to ever climb a particular mountain."
At the moment, the researchers have yet to determine the reason why the Antarctic forests disappeared with most other species during the Permian-Triassic mass extinction event. But Gulbranson noted that the trees in those polar forests were "extremely hearty," and able to survive in different environments.

"It's extremely rare, even today, for a group to appear across nearly an entire hemisphere of the globe," said Gulbranson.

At the time the Permian-Triassic extinction event took place, Antarctica was part of the supercontinent called Gondwana, a massive piece of land that also included other parts of the modern-day Southern Hemisphere, including South America, Africa, the Arabian Peninsula, India and Australia. The region benefited from warmer climate and greater humidity, and that allowed different mosses and ferns, as well as the extinct plant Glossopteris, to grow in the area. The UW-Milwaukee researchers also believe that the Antarctic forest may been expansive enough to cover all of Gondwana.

Comparing the Permian era's Antarctic forests to today's forests, Gulbranson explained that the ancient forests were less diverse, with fewer types of plants that had their own individual roles in how the whole forest responded to changes in climate and other environmental variables. These forests are also believed to have survived the completely dark months of winter and summer months without sunsets that are unique to the polar regions. Modern-day forests, on the other hand, have greater plant diversity, but are more sensitive to environmental changes.

Even with the prehistoric forests proving to be more durable, they failed to survive the cataclysmic changes that led to the Permian-Triassic mass extinction. Yet the Antarctic forests proved interesting in other ways beyond their resilience, as Gulbranson observed that the prehistoric trees took only about a month to transition from an active summer to a dormant winter, as opposed to how modern plants take several months to make the same kind of transition.

"There isn't anything like that today," Gulbranson observed.

"These trees could turn their growing cycles on and off like a light switch. We know the winter shutoff happened right away, but we don't know how active they were during the summertime and if they could force themselves into dormancy while it was still light out."
With the recent trip to Antarctica leaving some questions unanswered due to inclement weather and aircraft issues, Gulbranson added that he plans to return to the site later in November and stay through January of next year, in order to learn more about the Permian-Triassic mass extinction. He also hopes to use his subsequent findings to further understand how life on Earth is affected by greenhouse gases and climate change.

[Featured Image by Dorothy Chiron/Shutterstock]