The loss includes thousands of koalas, along with other species such as kangaroos and wallabies.

This has the potential to hasten koalas’ slide towards extinction in the wild in eastern Australia.

The fires have killed 26 people, destroyed 2,000 homes and scorched an area twice the size of Maryland.

The death toll for animals in Australia continues to go up.

The World Wildlife Fund in Australia estimates that as many as 1.25 billion animals may have been killed directly or indirectly from fires that have scorched Australia.

"The fires have been devastating for Australia’s wildlife and wild places, as massive areas of native bushland, forests and parks have been scorched," Stuart Blanch, an environmental scientist with the World Wildlife Fund in Australia, told USA TODAY. Many forests will take many decades to recover, he said.

The fires, which have been blazing since September, have killed 26 people, destroyed 2,000 homes and scorched an area twice the size of the state of Maryland. They have been fueled by drought and the country’s hottest and driest year on record, and exacerbated by climate change.

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The new number of animals killed was calculated using methodology that estimates the impacts of land clearing on Australian wildlife and extrapolates upon the science of Chris Dickman from the University of Sydney.

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Dickman told HuffPost that his original estimate of 480 million animals was not only conservative, it was also exclusive to the state of New South Wales and excluded significant groups of wildlife for which they had no population data.

That figure excluded animals including bats, frogs and invertebrates. With these numbers included, Dickman said, it was “without any doubt at all” that the losses exceed 1 billion. “Over a billion would be a very conservative figure,” he told HuffPost.

Blanch told USA TODAY that the loss includes thousands of precious koalas, along with other iconic species such as kangaroos, wallabies, gliders, potoroos, cockatoos and honeyeaters.

"There are estimates that up to 30% of koalas (as many as 8,400 koalas) may have perished during fires on the mid-north coast of New South Wales," Blanch said. "This is a devastating blow for a species already in decline due to ongoing excessive tree-clearing for agricultural and urban development, and pushes the species closer to becoming an endangered species.

"This has the potential to hasten koalas’ slide towards extinction in the wild in eastern Australia," Blanch warned.

Other species may also have tipped over the brink of extinction, he said.

Blanch added that "fires across Kangaroo Island in South Australia have been particularly devastating for wildlife: The severe loss of understory – the layer of vegetation under a forest – is a worry for the Kangaroo Island dunnart (a small, mouse-like creature) with some fearful the fires have pushed the species over the brink of extinction." A bird, the Kangaroo Island glossy black cockatoo, is also close to extinction and will need an immediate assessment when it’s safe to do so.

Fires have also burned through critical habitat of native Australian mammals such as the long-footed potoroo, the mountain pygmy possum, the yellow-bellied glider and the brush-tailed rock wallaby, and bird species such as the critically endangered regent honeyeater, according to the World Wildlife Fund in Australia.

Until the fires subside, the full extent of damage will remain unknown.

Australia, unfortunately, is no stranger to extinction: Some 34 species and subspecies of native mammals have become extinct in Australia over the past 200 years, the highest rate of loss for any region in the world, Dickman said.

Contributing: The Associated Press