The towering ancient bunya pine is known for its enormous cones and edible nuts, which make it central to a rich Indigenous heritage of meeting, feasting and trade.

Key points: Bunya pine trees have been dying in Queensland

Bunya pine trees have been dying in Queensland A soil-borne water mould called phytophthora is believed to be causing the dieback

A soil-borne water mould called phytophthora is believed to be causing the dieback The bunyas are significant for the Indigenous people across Queensland

But in the pine's home in southern Queensland's Bunya Mountains, an unprecedented dieback of the ancient trees has scientists and rangers worried.

It's believed an exotic soil-borne fungal-like organism called phytophthora has caused the death of around 50 bunyas, and there are concerns that the spread could continue.

Some of the dead trees are thought to be between 600 and 800 years old, and would normally live for more than 1000 years according to Louise Shuey, a plant pathologist with the Queensland Department of Agriculture and Fisheries.

Fifteen sites across the Bunya Mountains National Park appear to be affected by phytophthora, with infections confirmed at two of those sites, Dr Shuey said.

"It's killing quite a few trees. That's pretty devastating."

Because the symptoms of disease are hard to see from the ground, it's possible the bunyas were first infected several years ago. ( Supplied: Greg Carter )

'Tribal groups would travel for thousands of kilometres'

The Bunya Mountains were a significant place for Aboriginal people from all across Queensland, said Damon Miri Anderson, a Wakka Wakka man and Bunya Ranger.

"Tribal groups would travel for thousands of kilometres to come for gatherings, do tribal marriages, dispute differences, and trade," Mr Anderson said.

"A lot of the groups would camp in the foothills, and then travel up the mountain for ceremonies and corroborees, and to trade things.

"The coastal mob would bring fish and shells that other people couldn't find out west."

The gatherings in the Bunya Mountains were thought to be the largest meeting of Aboriginal people in Australia. ( Supplied: State Library of Queensland )

The Bunya Rangers formed in 2009 after some Elders were concerned about a lack of Aboriginal management in an important cultural place, said Paul Dawson, general manager of the Bunya People's Aboriginal Corporation.

"It was noticed there was some bunya dieback over the last decade — without anyone being alerted," Mr Dawson said.

"[The dieback] increased two or three years ago quite noticeably.

"It's a really important place so there is a lot of concern about the health of the bunyas."

Queensland Parks and Wildlife rangers and scientists from the Queensland Department of Agriculture and Fisheries are now investigating.

What is phytophthora or 'dieback'?

Phytophthora is a type of water mould, which behaves just like a fungus, but is in a completely different group of organisms called oomycetes.

It lives and is transported in soil, and attacks the roots of trees, eventually preventing the tree from getting any food or water.

The initial symptoms of infection are dieback of the tree crown — the top part of the tree — followed by death over a few months, said Dr Shuey.

"From the ground you can see that the leaves are starting to go brown and thin... but by the time you can see that, the disease is quite advanced," she said.

"We want to try and get some aerial mapping done so that we can find out where the disease is starting."

Dr Shuey collected soil samples from around the bunya roots to test for phytophthora. ( Supplied: Louise Shuey )

The species of phytophthora thought to be responsible for the bunya dieback is Phytophthora multivora, which has also caused dieback in the Wollemi pines in New South Wales, and the ancient kauri trees in New Zealand.

Hoop pines, another native tree, might also be affected by phytophthora dieback in the area, but rangers have not been able to access the sites to confirm reported observations.

The other main species of phytophthora present in Australia (it is an invasive species) is Phytophthora cinnamomi, and is responsible for extensive dieback in south-west Western Australia.

One of the first signs of phytophthora infection is leaf-browning. ( Supplied: Louise Shuey )

Drought, pigs and dirty shoes

The emergence of the plant disease is closely linked to environmental conditions, and Dr Shuey thinks the drought has contributed to the bunya dieback.

"There generally needs to be a period of wet which spreads the spores, and then a period of drought which we're going through right now," she said.

"This means that the infected trees [that] may normally be able to tolerate the infection might be under more strain now. And that's when you start to see the decline."

The Bunya Rangers are concerned about the time lag between identifying the disease and taking action to prevent its spread. ( Supplied: Louise Shuey )

It's suspected that feral pigs may be contributing to both the spread of disease and the declining health of the bunyas.

"It's been shown in New Zealand and in WA that pigs can actually spread phytophthora, and they also eat the bark and nuts," Dr Shuey said.

"But it may have also been brought in by hikers," she said,

"You should clean your shoes before you come into any national park, because we think that's how it got spread in New Zealand and maybe in New South Wales."

One management action is likely to be making sure soil particles aren't transported between areas on boots, equipment, or vehicles.

Preserving bunya trees and their stories

Aerial surveys have revealed 15 locations in the Bunya Mountains may be affected. ( Supplied: Greg Carter )

While there are still a couple of thousand bunyas in the Bunya Mountains, Dr Shuey is concerned the situation could get worse given the small native range of the tree.

"I guess we're worried because we've seen in the kauri forest in New Zealand how quickly this disease can start to spread," she said.

Phytophthora dieback has been detected throughout the kauri's native range in the upper North Island of New Zealand, where hundreds of trees have been wiped out.

Scientists will trial the use of phosphite — a fungicide — in plantation bunyas, with the aim of being able to control the spread of the disease in the wild trees.

The method, which stimulates the immune system of the plant, has been used on New Zealand's kauris, with some success.

Monitoring and testing of new areas is planned, and both the Queensland Parks and Wildlife Service and the Department of Agriculture and Fisheries have been meeting with the Bunya People's Aboriginal Corporation about management plans.

Scarring of a bunya tree believed to be made by Indigenous people to aid climbing to harvest bunya cones and nuts. ( Supplied: Louise Shuey )

While so far only a relatively small proportion of bunyas have died, each individual tree is significant to the Indigenous people of the region, said Mr Anderson.

"Individual trees are really sacred, and during the gatherings every family group would be given a specific bunya tree that they could climb and harvest off," he said.

"People talk about the rainbow serpent and different things from their country, well we are the people of the bunya — that's what we tell our stories about.

So when just one bunya tree dies, the loss of its important history is also felt, but preserved in the stories the Bunya People tell.

"We're educating the young generation on the risk of losing the bunyas, that we have to preserve our bunyas," Mr Anderson said.

"If it gets to the point where we don't have bunyas, we have to keep that songline and that story alive."

The bunya dieback highlights the importance of Indigenous peoples' connection to country, Mr Dawson said.

"Phytophthora is another indicator that the health of our country is in trouble, and we need to invest in Aboriginal people being on country and looking after it."