Koalas and kangaroos are spread out across the country, so they're not in danger of going extinct due to the blazes. But other animals that live in niche environments and have smaller populations may have been wiped out entirely; these include the eastern bristlebird, the mountain pygmy possum and the corroboree frog.
For these species, "if its habitat burns, it's a goner," Dickman said.
Extinction doesn't happen all at once. Each species on Earth has an average of 220 populations, so a healthy species could recover if only a handful of populations die out. But "if you whittle away population after population, then eventually you'll be left with half a dozen, then three, two, then maybe even one population," Dickman said. "Then all it takes is one event and it's gone -- a fire, drought, whatever."
Climate crisis and recovery in a changing landscape
These animals' recovery depends not only on their population size, but also on the condition of their habitat. For instance, plants grow slower in high-altitude alpine regions, meaning it could be a very long time before species are able to return.
Sometimes, even if a habitat heals, the animals don't come back. In 1993, a fire in NSW's Royal National Park wiped out the greater gliders -- a type of lemur-like gliding marsupial -- that lived there. "The population is effectively gone," Dickman said.
It's not that animals are unprepared for natural disasters -- they've been dealing with fires for millennia. But human interference has changed everything. We have fragmented natural environments with cities and residential areas, cleared land for our use, and introduced invasive species -- making it harder for native species to recolonize after fires.
Perhaps the most devastating human factor has been the climate crisis, which experts say has made natural disasters go from bad to worse. Australia is experiencing one of its most severe droughts in decades, and a heatwave in December broke the record for highest nationwide average temperature, with some places sweltering under temperatures well above 40 degrees Celsius (about 113-120 degrees Fahrenheit).
It's gotten so bad that the heat and drought were killing thousands of flying foxes even before the fires began. "They've been falling out of trees in large numbers," Dickman said. Their population is "almost certain" to have depleted further now that fires have burned their habitat.
The depletion of animals and their homes is a vicious cycle; just as animals need habitats to survive, so too do habitats need their animals.
For instance, a type of rat kangaroo called the potoroo is crucial to keeping forest soil healthy. If potoroos are hit by fire, some plant species might be unable to regenerate, which could then kill off other species that feed on vegetation. Ecosystems are built on balance -- once one element is thrown off, everything is affected.
Animal hospitals, zoos and rescue groups on the ground are doing their best to respond to the fire crisis, with local residents and volunteers pitching in to care for injured animals.
"This is huge because we had a drought before we had this bushfire, so the animals are already undernourished," said Janine Green, a volunteer at WIRES Wildlife Rescue, who rescued a possum with badly burnt paws on Tuesday near the NSW town of Cobargo.
Federal Environment Minister Ley said in December that the government is working with koala experts, and had allocated $6 million Australian dollars ($4.1 million) to establish habitat corridors and a plan for releasing animals that have been in hospitals.
But some fear that unless authorities take decisive long-term action on climate change and animal conservation, the country's wildlife and environment could face a dire future. Australia has more than 300 native species -- and about 81% of them are only found in the country. If they are wiped out here, these rare animals could be gone for good.
"They're not coping, and now they've got no grass, no water, no habitat," Green said. "Who knows if they can breed after this? We've never seen anything like this before."