Scientists at the University of Melbourne used new techniques to date fossilised pollen and reveal the Plain's 'big wet' - a dramatic transformation in climate that occurred around five million years ago.
The finding sheds new light on the environmental history of the Nullarbor, a former seabed that was lifted above the sea 14 million years ago. Bordering the Great Australian Bight it covers an area of 200,000 km2 between South and Western Australia.
Up until five years ago, the region was relatively dry with annual rainfalls of around 480 mm, but the study found that between 5 and 3.5 million years ago it became a forest of gums and banksias as annual rainfall rose to around 1220 mm.
Today, the Nullarbor is a treeless saltbush shrubland with annual rainfalls averaging 250 mm.
Investigating the climate history of Australia's desert regions is traditionally difficult for scientists, given the scarcity of fossils and the difficulty in accurately dating them.
The research focused their analysis on the Nullarbor speleothems (stalagmites, stalactites and flowstones), which previously could not be accurately dated beyond 500,000 ago.
However, the authors successfully applied new dating methods developed by Professor Jon Woodhead, a co-author of the study, to determine the age of older samples, which then were analysed for their pollen content.
This revealed the unique history of the region's climate.
Prof Woodhead said the research showed there was much more to the Nullarbor than its iconic landform.
"It is also home to a scientific treasure trove of palaeoclimate information that has potential global significance".
The study was published in the journal Proceedings of National Academy of Sciences of the United States of America.