Scientists are hoping they can study the surviving koala populations in the Pilliga to get a better understanding of how the animals are evolving to meet the current climate challenges.

The significant population drop of koalas, estimated to be at 80 per cent over three decades, in the once highly populated region has shocked scientists who observe the area.

In 1991 scientists surveyed the 535,000 hectare Pilliga Forests between Coonabarabran and Narribri - the largest remaining tract of NSW native forest, west of the Great Divide. Of 280 sites that were surveyed in the 1990s, 210 had evidence of use by koalas. But when the surveys were repeated in 2011 only 44 of those 210 sites still showed any sign of use by koalas - a reduction of nearly 80 per cent. Of the 70 sites that had no koalas in 1991 only one showed evidence of koalas in 2011. 

Dr Steve Phillips, is a wildlife ecologist who has spent his life studying Australia’s koala populations. and was one of the scientists involved in documenting the decline of the Pilliga koalas. He is deeply disturbed by the drop in the Pilliga populations. “The rate of the population decline has become quite scary.”

Dr Phillips said the drying out of the Western region, protracted drought, increased temperatures and large fire events had had a profound impact on the koala populations.

“Unlike other animals, koalas don’t have the physiological mechanisms to cope with the heat. They have a very fine physiological threshold. If it is very hot through the day, they need several hours of cooler temperatures at night for them recover. If they don’t get a reprieve from the heat they find it difficult to maintain a water balance and then need access to free-standing water.”

Dr Phillips is part of a number of scientists who undertake monitoring of our koala populations for the state and federal governments.

He said there had been widespread population attrition across the range of the koala in eastern Australia, but especially from the western areas.

“We know that there are a small number of koala colonies still alive in the Pilliga. But we’re unsure whether they are koalas with greater adaptability, and if that’s the case, they may represent the future of the species.”

Dr Phillips said where once there were thousands of koalas in the region, there were now just hundreds.

“It’s very important that we get as much information on the genetics of these outliers as possible. 

“We can find out a lot these days through the analysis of their scat – we can understand their DNA, disease status, and then we can get a greater understanding of what their survival looks like.

“The future is about looking at those species and asking what they can teach us about what they need to survive.”

Dr Phillips said the declining population of Australia’s koalas was not an isolated experience. “We’re seeing the same issue in possums and gliders. Once they are overheated and dehydrated it’s very difficult to save them.”

He said there were also impacts on the food the koala populations rely on, after ongoing droughts. “Eucalypts have evolved so that when they get stressed, they become toxic. And that’s when everything gets complicated.”

On ground support

While Dr Phillips said the declining native populations were distressing, there was hope. “We have detected new populations of koalas outside those areas we would normally find them,” he said, citing new information on sightings outside Moree.

“A lot of that information comes from the local farmers. And those farmers are certainly helping us with information, and by making water accessible to these populations.”

Dr Phillips is currently working with the NSW State Government on a strategy to abate the declining numbers.

The strategy is expected to be released in the first half of 2025.

“We’ve got to try and use the knowledge that we have, in the best way that we can to create a positive future for these animals.

“If they can’t adapt, they will die,” Dr Phillips said.

*If you would like to help, you can take note of your most recent koala sightings via the More here.