Critical forest habitat that is home to the Leadbeater’s possum, Victoria’s faunal emblem, is almost certain to “collapse” due to logging and fires, new research has found.

A study of 157,000ha of mountain ash forest in the central highlands of Victoria found that all 39 modelled scenarios of the habitat’s future found at least a 92% chance it will collapse within the next 50 years.

Researchers from the Australian National University used criteria deployed by the International Union for Conservation of Nature (IUCN) when assessing the health of ecosystems. Under this methodology, the central highlands area is “critically endangered”, the report states.

When current logging practices are factored in, there is a 97% chance the ecosystem will collapse, while the addition of a major fire event, such as the Black Saturday fires that tore through the forest in 2009, ups the risk to 99%.

The “collapse” of the ecosystem is measured by its ability to provide a proper habitat for the biodiversity that relies upon it. Specifically, the loss of old, hollow-bearing trees would be disastrous for the Leadbeater’s possum, which numbers just 1,500 animals.

Mountain ash trees are the world’s tallest flowering plant, reaching up to 50m tall within 35 years of germination. Some have been measured at more than 100m tall following several hundreds years of growth.

These old-growth trees covered around 4% of the central highlands area in 1964 but by 2011 this proportion had shrunk to 1%. This is not only significant for the Leadbeater’s possum and other animals, but also because the forest regulates the health of Melbourne’s main water catchment and is seen as an increasingly important carbon storage area.

The report states “there needs to be greater protection of remaining areas of unburned forest, and restoration activities in parts of the forest estate. Implementation of these strategies will require a significant reduction in logging pressure on the mountain ash ecosystem.”

Emma Burns, lead author of the report, said logging practices were effectively stripping away the next generation of aged trees, leading to a future dearth of old-growth forest.

“Trees aren’t getting old because they are being logged, which means extinction will follow for the Leadbeater’s possum,” Burns told Guardian Australia. “We’ve got a vulnerable and endangered possum and the ecosystem itself is critically endangered, so I’m not sure what else we need to know to make sure we do things differently.”

Burns said the report will be raised with the IUCN and the Australian government. If either decides to list the ecosystem as critically endangered it will ensure products made from the forest, such as Reflex paper, are unable to gain sustainable forest accreditation.

Environmental groups have called for all logging in and around the Leadbeater’s possum habitat to cease and have campaigned for the creation of a new national park in the area.

A spokesman for VicForests, the state logging agency that operates in the central highlands, said the level of mountain ash forest harvested is at its lowest point in 20 years.

“More than 30% of each area planned for harvest is retained during operations, to protect environmental values including hollow-bearing trees used as habitat by native fauna,” he said. “This retained forest is left standing to become future old-growth across the landscape along with forest in the national park and reserve system.

“We are also undertaking collaborative research with scientists from a range of organisations, including the University of Melbourne, to look at ways to accelerate the development of hollows in younger forest and provide additional habitat for species such as the Leadbeater’s possum.”