Claims that koalas are ‘functionally extinct’ after the bushfires are overstated. But there are very real threats to their future

Koala factcheck: have the Australian bushfires put survival of the species at stake?

Hundreds of koalas have been killed and millions of hectares of their habitat destroyed in the bushfires that have swept across parts of Australia this month.

A recent headline in Forbes alleged the fires had rendered koalas “functionally extinct”, a claim that was repeated widely in Australia and overseas, including by the Daily Mail and news.com.au.

The claim, which originated from a release in May by the Australian Koala Foundation, has been criticised by koala experts and science commentators for overstating the plight of the popular marsupial.

So what is the truth about the threats to Australia’s koala population?

Are koalas ‘functionally extinct’?

The short answer is no.

Koala populations are in trouble, but this is due to a gradual process of deforestation over many years. This has been made worse by the recent fires, but the full scale of the damage is not yet known.

Stuart Blanch from WWF Australia says if a population is no longer genetically viable, koalas could be said to be “functionally extinct” in some areas.

“But there are large areas of large numbers of koalas that are still viable,” he says. “And they are our hope.

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“Generally the animals that are considered to be functionally extinct are down to a few hundred, or dozens, like the Sumatran rhinoceros. For koala populations, there are disputes about how many are on the east coast, but the best evidence we have is 15,000 to 28,000 koalas in New South Wales.

“We are cautious about these numbers, but we are not down to hundreds of koalas. We don’t want to undermine the good efforts of people trying to save koalas, but the language is important. We absolutely believe there is hope to stop koalas going extinct.”

But Blanch and the WWF fear koalas are heading towards extinction by 2050 if the destruction of their habitat continues.

“Largely what is driving the koala to extinction is deforestation,” he says. “The climate-heating impacts of drought and bushfires and declining water availability is making that trend worse in some areas.”

What was the effect of the recent bushfires?

Blanch says the full scale of this month’s bushfires is not yet known, although news reports have referred to fears that hundreds of koalas may have died.

“I have seen estimates as to how many koalas have been killed, but I don’t think anybody knows. Or how much habitat has been burnt,” he says.

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“Eucalypt forests are adapted to regrow after fire, but we are seeing very hot firestorms that can kill trees. At the moment nobody knows what proportion of trees will regrow after being burned.”

He says at least 2m hectares of bushland have been burnt, with an average tree density of 150 a hectare.

“Broadly 300m trees have been affected by fire,” he says. “The vast majority will regrow, but increasingly we’re seeing trees killed by fires because they are too hot and they stop the shoots resprouting from their stems – 300 million trees is a lot of habitat, but that is not all koala habitat.”

Facebook Twitter Pinterest A bushfire burns in koala habitat near Port Macquarie earlier this month. Photograph: Saeed Khan/AFP via Getty Images

How is climate change affecting koala populations?

Koala populations across Queensland and NSW fell 42% between 1990 and 2010, according to the federal threatened species scientific committee.

James Tremain, a spokesman for the NSW Nature Conservation Council, says koala decline has been happening “slowly and silently”.

“Koala numbers have plunged over the past 20 years and if we don’t turn the trend around they won’t be ‘functionally extinct’, they will be actually extinct,” he says.

“We are directly destroying thousands of hectares of their forests through clearing for agriculture and logging for timber. But we are also shrinking available habitat indirectly as a result of climate change.

“The Pilliga forest near Narrabri in the north-west of the state is a good example. It used to have one of the biggest populations of koalas in the state. Now that population is almost gone because a few big heatwaves killed most of them off.”

This is one of the “insidious” impacts of global heating that many people would not have known about.

“Koalas, like all animals, can only survive within a fairly narrow temperature and rainfall range. Koalas simply can’t tolerate more than three or four extremely hot days in a row. These long heatwaves are becoming more common in the state’s west, which means koala populations are shrinking to the east along the coast.

“These processes doesn’t make the 7pm television news because they happen slowly and silently. That’s the nature of extinction: it happens quietly while no one’s watching.”

How can we rebuild koala populations?

Blanch says there are many examples of koala populations recovering thanks to reforestation.

“The rule of thumb has been you need 500 animals in an interbreeding population to have the genetic integrity to avoid inbreeding,” he says. “There are quite a few populations in that scale.

“The other requirement is there is extensive connected habitat, which is an issue about land clearing. You can bring more koalas back if you stop bulldozing trees and start letting trees regrow.”

He cites Armidale in northern NSW and Campbelltown in south-west Sydney as areas where koala populations have grown beyond 500.

“Those are two examples of where koalas do not have to go extinct. They will only go extinct if we make them.”