Australian wildlife rescuers estimate about a thousand koalas have died in bushfires that tore through major breeding grounds.

But Nicole Blums, of The Rescue Collective, told Simon Barnett and Phil Gifford it's hard to pin down an exact number.

She says some fires were so hot, they haven't even left bodies behind.

"Entire ecosystems have been wiped out. When you consider the amount of fires, how large and how spread they've been, the best way we can describe it is as a wildlife apocalypse." 

The fires have stoked fears that the national icon is getting closer to extinction.

"In what is a national tragedy, the bushfires in and around Port Macquarie in November devastated a genetically diverse koala population," Port Macquarie Koala Hospital said.

"As many as 350 koalas have perished, with approximately 75% of the fireground footprint being prime koala habitat."

LISTEN ABOVE