Nearly three billion animals - including mammals, birds, reptiles and frogs - were impacted by the emergency between late November and February WWF-Australia said on Monday.

That figure was unchanged from its interim report released in July.

But the koala numbers in the final report are new and reinforce the devastation caused by the fires.

The worst losses - some 40,000 deaths - occurred on Kangaroo Island in South Australia, followed by Victoria with 11,000 koala fatalities and NSW with almost 8,000.

WWF-Australia CEO Dermot O'Gorman said koalas in NSW and Queensland were in rapid decline before the fires.

"Sixty thousand koalas impacted is a deeply disturbing number for a species already in trouble.

"That's why WWF has just announced Koalas Forever - a bold vision to double the number of koalas in eastern Australia by 2050," he said in a statement on Monday.

The plan includes a trial of seed dispersing drones to create koala corridors and the establishment of a fund to encourage landowners to create koala safe havens.

"It's part of WWF's Regenerate Australia plan - the largest and most innovative wildlife and landscape regeneration program in Australia's history," he said.

"WWF is determined to help restore wildlife and habitats, rejuvenate communities impacted by the bushfires, boost sustainable agriculture and future-proof our country," Mr O'Gorman said.

The overall estimated animal impact remains nearly three times that projected by Australian mammal expert Professor Chris Dickman in January.

WWF-Australia had commissioned a group of scientists to provide a more detailed estimate of the number of animals killed or displaced by the 2019-20 bushfires.

The report examined 11.46 million hectares of fire impact area and found nearly three billion native animals would have been within the forests and woodlands that burnt.

This includes 143 million mammals, 2.46 billion reptiles, 180 million birds and 51 million frogs which are thought to have been in the path of the fires.

In the final report, scientists drill down to reveal the impact on some individual animal species and groupings of species, including koalas.

The impact toll includes:

* nearly 40 million possums and gliders;

* more than 36 million antechinuses, dunnarts, and other insectivorous marsupials;

* 5.5 million bettongs, bandicoots, quokkas, and potoroos;

* 5 million kangaroos and wallabies;

* 1.1 million wombats;

* and 114,000 echidnas.

While Prof Dickman in January had estimated more than one billion animals perished in the Black Summer fires he had noted that figure was conservative and covered only the areas burnt in NSW and Victoria.

While scientists can't confirm exactly how many animals died, the prospects for any wildlife that did escape were "probably not that great" because of a lack of food and shelter, he added.

The WWF-Australia report recommends improving the management of future bushfires and the impacts on biodiversity by establishing rapid response teams to mitigate impacts on threatened species and identifying and protecting unburnt habitat.

WWF-Australia noted its report was restricted by limited data on animal densities, fire impacts and the ability of different species to survive and recover.

Australian Associated Press