Last chance to see? World’s biggest flowering trees grow in Tasmania

The tallest living tree in Australia is a Tasmanian giant ash hundreds of years old named Centurion, according to a survey decades in the making.

The tree was 99.6m tall when researchers and citizen scientists first measured it, but it has since lost a branch and a few metres of height – now rearing 96.5m above the ground.

Massive eucalypts like it face dire threats from fire, but there are ways to protect them, according the team.

The researchers have documented a crowd of other colossal Tasmanian in a paper published in the Australian Journal of Botany.

“A lot of people don’t realise that Australia, and Tasmania in particular, is actually an epicentre of the absolute largest flowering plants in the universe,” senior author Professor David Bowman, a researcher at the University of Tasmania, tells Cosmos.

The team found 18 trees that stretch over 90m tall, and 32 trees with a trunk volume over 250m³. Most of the tallest trees were Eucalyptus regnans, but the survey found a few other eucalypt species – globulus, obliqua and tasmaniensis towering above 85m or with volumes above 280m³.

It’s their volume and age that makes the trees remarkable, according to lead author Brett Mifsud.

“They can’t get to that size in under, say, 450-500 years. They grow tall in much less time, but they can’t get that big,” Mifsud tells Cosmos.

Mifsud, who works as a school teacher, has spent 35 years locating and measuring the Tasmanian giants in his spare time.

“This is citizen science on steroids,” says Bowman, who refers to Mifsud as a “hero”.

Mifsud says his interest was first sparked by photos of giant Victorian trees from the late 19th century, all of which have been lost to human activity and fire.

“Thankfully, because Tasmania had less of the catastrophic fires and land clearing in their Eucalyptus regnans forest than Victoria, they still had some old growth trees that pretty much are of the same stature of those big old trees that we’d seen in photographs from Victoria.”

The last survey of tall Tasmanian trees was published in 2000. Mifsud sought to update the ledger, recording the size and condition of Tasmanian trees.

A ground-based measurement using a laser is sufficient for measuring a lot of tree heights, but Mifsud says the most accurate way to measure the very tallest trees is still to climb them.

Climbers get as close to the top of the tree as they can, touch the top with a pole, and then drop a tape to the ground so it can be measured.

While Mifsud says he “loves being up there”, it can be daunting. Smaller trees can sway with the wind in a sickening way, and there’s a risk of disturbing animals on the climb.

“There’s places humans shouldn’t be, and climbing eucalypts to 80 or 90m is probably one of them,” says Mifsud.

“I don’t like to be up there too long… but it’s an amazing place to see.”

Other measurements can be done closer to the ground.

“We do a series of wraps with the tape around the trunk to get a series of diameters and we create a model of the tree using that,” says Mifsud.

“Then at the base, we use LIDAR scanning and photogrammetry to create a 3D model.”

The most massive trees are also, increasingly, the most vulnerable to fire. According to the research, 60% of the largest known trees have been lost to fire since 2004.

“The problem with being a 500 year old eucalypt is you’ve suffered a lot,” says Mifsud.

Old eucalypts, he says, develop hollows around rotting places, leaving perfect gaps for even low intensity fires to cause a lot of damage. Climate change is making the risk significantly worse.

“The rainfall totals are going down. Things are drying out,” says Mifsud.

“It’s last chance to see, if the worst case scenario happens. Hopefully we put in place plans for some protection.”

Bowman wants to see stakeholders joining forces to protect the giant trees.

“Everybody knows they’re important. They have high value, and they potentially a really useful part of you know, the tourist experience of Tasmania,” he says, adding that both management strategies like logging buffers, and volunteer-led protection efforts like fire-proofing or irrigating could help.

Other significant trees, like Wollemi pines and California redwoods, have similar fire management plans.

“Just having a reserve and thinking the reserve is going to protect them is old school thinking. It’s not dealing with climate change,” says Bowman.

Mifsud cites the photography of Nicholas Caire as a major inspiration for his work – and a warning. Caire snapped images of giant Victorian trees in the late 19th and early 20th century in the hope their memory would be preserved, even as the trees disappeared.

“I hope that that my paper doesn’t do the same thing. There’s no Victorian giant trees of the stature of the top 40 trees in Tasmania, for size left,” says Mifsud.

“I’d really like to see all land holders, both state forest and parks, get behind a push to make sure that we’ve got them into the future.”