Scientists have discovered prehistoric fossils in Antarctica that reveal that the frozen continent once had tree-filled forests. The team estimates that Antarctica's trees grew around 260 million years ago, during the Permian Period – this was even before dinosaurs existed.
The Permian Period ended in a historic mass extinction, when over 90% of our planet's species, including polar forests, were wiped off the face of the Earth. Scientists believed the mass extinction occurred as Earth's climate rapidly shifted from icehouse to greenhouse conditions. The discovery could help researchers uncover what life was like on our planet before the historic mass extinction.
About 13 fossils were discovered by the University of Wisconsin-Milwaukee (UWM) geologists Erik Gulbranson and John Isbell, who climbed the frozen Transantarctic Mountains for the study. "People have known about the fossils in Antarctica since the 1910-12 Robert Falcon Scott expedition," Gulbranson, a paleoecologist and visiting assistant professor in UWM's Department of Geosciences, said in a statement. "However, most of Antarctica is still unexplored. Sometimes, you might be the first person to ever climb a particular mountain."
Researchers believe that the prehistoric Antarctic forests grew extremely rare and robust trees, capable of surviving various kinds of environments. "This plant group must have been capable of surviving and thriving in a variety of environments," Gulbranson said. "It's extremely rare, even today, for a group to appear across nearly an entire hemisphere of the globe."
A warmer and more humid Antarctica
Antarctica was a much warmer and more humid place as the Permian Period came to an end. During this time, the world's continents, instead of being scattered across Earth, were instead banded closely together, as part of two massive landmasses. Antarctica was part of the massive southern supercontinent Gondwana, which also included present-day South America, Africa, India, Australia and the Arabian Peninsula.
According to the researchers, the Antarctic forest fossils appear different than present-day high-latitude forests that boast of a variety of diverse plant species. During the Permian Period, forests had lower plant life diversity. The forests had groups of plants with specific functions that "affected how the entire forest responded to environmental change".
The prehistoric Antarctic plants would also have had to survive the polar extremes of constant darkness and perennial light. Despite being warmer, as being a part of the polar regions, Antarctica would likely have experienced months of complete darkness in the winter and continuous daylight during the summer.
Surviving extreme temperatures and environmental changes likely made the trees evolve into highly adaptable species. Scientists found that the trees could rapidly transition from summer activity to winter dormancy. While present-day trees take several months to make the same transition, the ancient trees completed it within a month.
"There isn't anything like that today," Gulbranson said. "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."
Researchers hope that the forest fossils can also reveal more about what caused the mass extinction at the end of the Permian Period and how climate change can affect life.
"This forest is a glimpse of life before the extinction, which can help us understand what caused the event," Gulbranson said. "The geologic record shows us the beginning, middle and end of climate change events. With further study, we can better understand how greenhouse gases and climate change affect life on Earth."