Curtin University researchers measured iron-rich rocks that suggest the previously lush Nullarbor became one of the earth's most arid environments between 2.4 and 2.7 million years ago.

Geochemist Milo Barham said gas locked in the ancient rock helped provide a much clearer time frame than geoscientists had previously been able to determine.

"The amount of helium trapped in these iron-rich horizons can be used to determine when they were formed," he said on Tuesday.

"Exposing these relics of drying to a tiny laser releases helium, which we can measure to constrain the timing of these dramatic environmental responses to Earth's climate history."

The Nullarbor was once a lush vegetation-dense forest of gums and eucalyptus trees and other flowering plants now found on Australia's east coast.

The changing climate included less rainfall and a dramatic decline of groundwater as sea surface temperature decreased.

Determining when it changed can help explain the impact on biodiversity in the area and provide a time frame for the evolution of several native species.

Geochemist Maximilian Drollner said about half of the earth's land surfaces were considered drylands, and changes to the areas have significantly impacted societies, landscapes and regional biodiversity.

"The drying of Australia's interior separated the common ancestors of many species that once roamed freely across Australia," he said.

"This separation led to the independent evolution of these isolated populations on the east and west coasts, eventually resulting in distinct species or sister species."

Dr Drollner said there were many examples of sister species of birds, insects, and plants that have common ancestors living thousands of kilometres apart after they were separated by "by environmental barriers created through ancient climate change".

The research was published in Geophysical Research Letters.

Australian Associated Press