They discover how Australia went from lush to desert

18 Apr. (EUROPE PRESS) –

A new approach, applied to Australia’s Nullarbor Plain, sheds light on how the ancient climate change it gave rise to some of the driest regions on our planet.

Researchers at Curtin University used iron-rich layers formed in ancient sediments to pinpoint when an area dried up in response to climate changes, such as the drastic decline in groundwater in South Australia. They publish results in ‘Geophysical Research Letters’.

These “relics of desiccation” suggest that the Nullarbor changed drastically to dry conditions between 2.4 and 2.7 million years agoand discover how these environmental changes were key in the formation of Australia’s diverse flora and fauna.

Dr Maximilian Dröllner, lead author of the study and a member of the Time Scales of Mineral Systems Group at Curtin’s Faculty of Earth and Planetary Sciences, says that defining when climate change occurred in ancient landscapes it had posed quite a challenge to geoscientists around the world.

“Almost half of the planet’s land surface is considered arid and some 3 billion people live there,” explains Dr. Dröllner. “Changes in these drylands can profoundly affect both our society and regional biodiversity, and aridification has contributed decisively to shaping the landscapes and ecosystems we see today“.

Determining when climate events occurred in drylands has been a difficult task for geoscientists, as researchers have relied on indirect observations, such as marine sediments from neighboring areas.

Co-author Associate Professor Milo Barham, also of Curtin’s Mineral Systems Time Scales Group, notes that directly measuring the products of desiccation of landscapes can provide a much clearer time frame.

“The amount of helium trapped in these iron-rich horizons can be used to determine when they formed,” said Associate Professor Barham. “Exposing these ‘relics’ of desiccation to a tiny laser releases helium, which we can measure to timing of these dramatic environmental responses to Earth’s climate history.”

Determining when these events occurred can help explain how they affected the biodiversity of the area and, especially in the case of South Australia, provides a time frame for the evolution of several native species.

“The desiccation of the Australian outback separated the common ancestors of many once free-roaming species,” Dröllner said. “This separation led to the independent evolution of these isolated populations on the east and west coasts, eventually giving rise to distinct or sister species“.

“Today we see many examples of sister species of birds, insects and plants that have common ancestors but now live thousands of kilometers apart, separated by environmental barriers created by ancient climate changes.”