The Morrison government will provide $50 million to support ecosystems and threatened species harmed by the country's largest ever bushfires.

Treasurer Josh Frydenberg and Environment Minister Sussan Ley will on Monday detail what the government is describing as a "downpayment" to aid wildlife across states and territories.

An injured koala being treated on Friday at the Kangaroo Island Wildlife Zoo in South Australia. Credit:Getty Images

“This initial investment of $50 million into the protection and restoration of our wildlife and habitat is a critical step in creating a viable future for animals that have survived," Mr Frydenberg said in a statement, ahead of a media event planned for the NSW city of Port Macquarie.

With huge fires still active in several states - particularly in NSW, Victoria and South Australia - the full toll on ecosystems is still unknown.