Antarctica is arguably one of the most barren, extreme environments on the planet, with only one permanent terrestrial resident – the Emperor penguin. However, wind the clock back 90 million years, and the continent was far from a frozen wasteland. New evidence has suggested that this icy continent was largely covered in tropical swamp forest, during the time of the Dinosaurs.
The cretaceous period, which spanned from approximately 145 to 66 million years ago, was a very warm period in earth’s history, with an almost worldwide greenhouse climate, and an abundance of vegetation and tropical forests. Antarctica at this time was mostly covered in a swampy, tropical forest and there were no glaciers at the south pole.
Scientists at the Alfred Wegener institute, Germany, made this discovery by analysing sediment cores drilled from the seafloor in West Antarctica. These cores show a glimpse of the past environment in Antarctica, with sediments nearer to the bottom of the core representing older geological time. At three metres down on the core, representing the late cretaceous period, the sediment composition changed drastically, composed mainly of a coal-like material, soil, roots and pollen. The team identified over 65 types of plant material, indicating the presence of an ancient conifer forest.
So, what exactly lived in these forests? The forests would have likely been very similar in plant structure to some of the forests in modern-day New Zealand, dominated by towering tree ferns, cycads and coniferous trees. At this time in history, flowering plants had only recently evolved so were likely rare in these forests. Biogeochemical evidence from the sediment cores also revealed that microscopic photosynthetic life such as algae and cyanobacteria were common in warm lakes and rivers.
These forests were dominated by a variety of dinosaur species, which filled many of the ecological roles of forest ecosystems today. There were giant herbivorous dinosaurs such as the long necked Austrosaurus, and Muttaburrasaurus, a close relative of the Iguanadon, whose remains are commonly found on the Isle of Wight. There were also carnivorous dinosaurs such as Cryolophosaurus and Australovenator, and the tiny herbivorous Leaellynasaura, which likely lived in small groups in the forest. Primitive mammals shared the forests with the dinosaurs; they were furry, egg laying species which were likely similar to modern echidnas and platypus. It is also known that the river networks around these forests were home to a giant salamander-like amphibian called Koolasuchus, belonging to an ancient lineage of animals over 250 million years old.
The discovery of these polar forests is not only an exciting advance for palaeontology, but also shows us how key carbon dioxide levels are in the shaping of an environment. It is known that the tropical climate during the cretaceous period could have only been possible if carbon dioxide levels were much higher than today, so this discovery could give an insight into the future environmental implications of increased carbon dioxide levels in the near future.
