Hundreds of ancient bunya pines in a Southern Queensland National Park are facing a growing threat as wet weather heightens the spread of an invasive soil-borne disease.
The recent rain and upcoming third La Niña summer present the perfect conditions for phytophthora to spread which has researchers, park rangers and traditional owners of the Bunya Mountains National Park worried.
With hundreds of bunya pines already infected, rangers have called for tracks to be closed during wet weather to help limit the spread.
But for the Bunya People's Aboriginal Corporation general manager Paul Dawson, the loss of the trees has a deep spiritual cost.
"It's more widespread than initially thought," Mr Dawson said.
"Losing the Bunyas would be like losing a family. That's the fear and, I think, a justified fear."
First the rain, then the deathly dry
The invasive soil-borne microorganism was first found in the Bunya Mountains in 2011, believed to have spread from enormous rain events of that year.
Since then, about 50 sites have been identified with four to 15 trees infected at each location.
The disease causes leaves at the crown of the tree to discolour and can cause it to die within a few months.
Plant pathologist with the Queensland Department of Agriculture and Fisheries, Dr Louise Shuey said it was dry periods after rain when symptoms of this disease were most obvious.
"There's now probably a new infection event happening… it's ideal conditions and it might start spreading again," Dr Shuey said.
"If there is another drought episode that comes up, we will see more deaths.
"In the next few months is probably the time that we might need to start treating these trees to see if we can save them."
How else does it spread?
Phytophthora is spread by feral pigs, as well as the movement of soil on shoes and bikes.
The National Parks and Wildlife Service has established boot and bike washing stations across the Bunya Mountains to help limit the spread of disease.
The wetter than average conditions have also provided an optimum breeding environment for feral pigs, with numbers booming in the national park.
Darren Marshall, from Southern Queensland Landscapes, said with increased funding, tracking and poisoning methods would be rolled out.
"These pigs don't listen to boundaries, they go wherever they want," he said.
"We put tracking collars on the feral pigs, those collars take a GPS point every half an hour for the rest of that pig's life.
"It gives away their food source, their shelter sources, water sources and most importantly, it gives away where the pigs feel most comfortable and safe."
Hope in sight
While uncertainty remains over the future for the region's Bunya trees, there is hope with new treatments being investigated.
Phosphide injections have been trialled in a tree plantation in southern Queensland which, if absorbed by the roots, can function as a physical barrier to stop new infections of phytophthora.
The chemical stimulates natural defence properties in the bunya pines, which does not kill the disease but helps prevent the trees from succumbing to phytophthora.
About 120 trial trees have been injected with different dosage rates, at different times of the year.
Dr Shuey said the results had been promising.
"The Bunya and Hoop [pines], they seem to tolerate the phosphide injections really well," Dr Shuey said.
"I want to make sure that any treatment we propose, is the most environmentally friendly, it is a beautiful, unique national park and I definitely don't want to cause any harm.
"But I feel if we don't treat them soon, we'll lose even more Bunya pines."
Editor's note 21/9/2022: This story has been amended to remove a reference to Paul Dawson's Indigenous heritage, which was incorrect.
