Thousands of people will flock to national parks across Tasmania later this month to take in the autumnal scenes of fagus.

It is one of only a handful of winter deciduous trees in Australia, and turns bright orange for a short time during autumn before dropping its leaves.

Turning of the fagus is an annual pilgrimage for many, and about 3,000 people are expected to visit Mount Field over one weekend.

But there's a more sinister side to the deciduous beech and its future — scientists have warned that if not wiped out by bushfires, fagus will become a victim of climate change.

Rachel Power is expecting 3,000 people to visit the national park to see the fagus turn. ( Supplied: Rachel Power )

Celebrating the fagus

Along with Cradle Mountain, Mount Field is a fagus hotspot.

On April 27 and 28 the tree will be celebrated with live music, a treasure hunt and roaming rangers to educate visitors.

Rachel Power from the Waterfalls Cafe inside the national park said the turning of the fagus was a special time of the year.

"It's such an amazing atmosphere when people come through because the site is just spectacular," she said.

"It's quite a remarkable sight, when you get up there and you're immersed in it and the colour is all around you."

The fagus can be viewed from several places near Mount Field, and there's already colour emerging.

Scientists say Mount Field is a globally important refuge for ancient trees. ( ABC News: Peta Carlyon )

Living fossil

While fagus is visually impressive, it is significant for more reasons than its beauty.

There is evidence that it has been in Tasmania for 40 million years, according to Greg Jordan, head of biological science at the University of Tasmania.

"It's a beautiful thing that lives in a beautiful place, and it does a thing that in our part of the world is unique — it loses its leaves.

"The fagus is one of the last living species of an ancient and widespread group of plants."

Fagus likes cold, moist alpine areas. ( Supplied: Professor Greg Jordan )

Nothofagus gunnii and its close relatives were once widespread throughout the Southern Hemisphere.

"There's fossils from all over Australia, Antarctica and the south of South America," Dr Jordan said.

"The fagus was part of what is a rainforest community that now, as the climate became drier and more fire-prone over the past few million years, has contracted to places where it was wet enough and had very few fires.

"There's only a few places where that happens, those special pockets of western Tasmania are where that happens and where a whole bunch of really important species occur."

Bleak outlook

Fire and climate change are the two main threats to fagus, which were not unrelated.

Tasmania's remote wilderness has experienced two large fires in five years, including one this year that reached parts of Mount Field.

"As we've seen in the past few years, we're starting to get more and more fires," Dr Jordan said.

Fagus is Australia's only deciduous winter tree. ( Supplied: Professor Greg Jordan )

On one night in January this year, 1,500 dry lightning strikes were recorded across the state and 500 the following day.

"Until about 15 years ago, dry lightning was a rarity in western Tasmania," Dr Jordan said.

Fire specialist David Bowman said fagus did not recover from fire.

"Even a fire once every 1,000 years, it's not designed to resist fire," said Mr Bowman, who described fagus as a refugee from Antarctica.

"They're effectively a living fossil.

"Climate change will eventually knock it off, but the fire threat will be more immediate.

"These trees are only just holding on."

Part of an 'ancient system'

Fagus is part of an ancient system of plants living together.

Along with pencil pines and King Billy pines, the trees have been living in the same habitat for millions of years, Dr Jordan said.

"They're all at threat," he said.

"It won't be one year, it won't be 10 — it might be 100."

Dr Jordan said the ancient tree community was best exemplified at Mount Field.

"Mount Field is where you get all of those ancient things together and it's a globally really important place."