It has raised the figure mainly because researchers have now assessed the total affected area rather than focusing on the most affected states.

"This ranks as one of the worst wildlife disasters in modern history," said WWF-Australia Chief Executive Officer Dermot O'Gorman.

The WWF said it used various techniques to estimate animal populations, including using data from over 100,000 surveys. It said models could then accurately estimate animals found in areas destroyed by fire.

Project leader Lily Van Eeden from the University of Sydney said the research was the first continent-wide analysis of animals impacted by the bushfires.

"Other nations can build upon this research to improve understanding of bushfire impacts everywhere," she said.