Fifteen of Australia's tallest trees have been found destroyed after Tasmania's summer bushfires, tree enthusiasts say.

Key points: Sustainable Timber Tasmania protects trees taller than 85m or 280 cubic metres of volume

Sustainable Timber Tasmania protects trees taller than 85m or 280 cubic metres of volume Two tree enthusiasts say 15 of those trees have been destroyed

Two tree enthusiasts say 15 of those trees have been destroyed Australia's tallest tree, Centurion, is scorched but still alive

The Riveaux Road fire in south-west Tasmania burnt almost 64,000 hectares of bush in summer, damaging eucalypts in the Huon Valley area, south of Hobart.

Giant tree enthusiasts Brett Mifsud and Russell DuGuesclin have now surveyed the damage.

To be protected, trees must be taller than 85 metres, or have 280 cubic metres in volume.

According to Sustainable Timber Tasmania, which manages the state forest, 180 Tasmanian trees meet that criterion.

But Mr Mifsud and Mr DuGuesclin discovered 15 of those giants had been destroyed.

'Prefect' among giants to fall

Mr Mifsud, who first visited Tasmania to look for giant trees 27 years ago, said the fallen giants had names like Bigfoot, Masters Bennett and Swearing Bob's Beast.

They had heights up to 87 metres and widths up to 20 metres.

Brett Mifsud (left) and Russell DuGuesclin have been chasing trees for years. ( ABC News: Mitchell Woolnough )

One tree that didn't survive was called the Prefect — a 500-year-old giant with a base 19 metres wide.

Mr Mifsud said he once wanted the climb the Prefect, but this time he visited, found a blackened stump and a tangle of dead branches and leaves.

The massive fluted base of the Prefect. ( Supplied: Brett Mifsud )

Mr Mifsud is a happy, talkative man but his shoulders dropped when he saw the remains.

"[It's] pretty disappointing. As we were walking up, we saw some live forest that hadn't been burnt," he said.

"But when you see this, it's a little bit depressing because that could mean a lot of our biggest trees could be looking a lot like this.

"This is one of our top 20 trees in Australia for size and now it's just a pile of ash really."

The Prefect — burnt in summer bushfires. ( Supplied: Brett Mifsud )

Mr DuGuesclin has travelled to Tasmania from Perth for 17 years to find the biggest trees in the southern hemisphere.

"The trees are much bigger and more impressive, so it's a mystery how it doesn't seem to be promoted much at all," he said.

One giant that was promoted was the Arve Big Tree.

At 87 metres tall, it survived bushfires in 1967 — but the 2019 blaze killed it.

Tasmanian forests were damaged by the blaze. ( ABC News: Mitchell Woolnough )

Suzette Weeding, the head of land management at Sustainable Timber Tasmania, said everything that could have been done to protect the trees had been.

"It is an incredibly difficult situation to go in and protect individual trees in a forest fire situation," she said.

"Especially one of that scale when there's a range of priorities being protected and to be managed, including life and infrastructure, and everything that could be done was done."

This giant, Rullah Longatyle (Strong Girl) was felled during the recent bushfires. ( Supplied: Russell DeGuesclin )

Hopes of new life

But in the ashes of the Prefect, Mr Mifsud found new life — tiny seedlings.

"There are eucalyptus regnans seedlings — exactly the same species as this massive tree here [Prefect], just 500 years younger," he said.

Russell DuGuesclin finds giant trees and measures them for the record book. ( ABC News: Mitchell Woolnough )

But a fire scientist at the University of Tasmania, Professor David Bowman, warned that climate change could bring more dry lightning strikes, like the ones that caused the blazes over summer.

"The environment these trees [are] in is going to be dryer and warmer and more fire prone because of more lightning-ignited bushfires," he said.

"So what we have to do is intervene in the field to provide fire breaks, change fuel, maybe irrigate do all sorts of radical interventions."

Ms Weeding said land was already cleared around Australia's tallest tree Centurion in the 2019 blaze and retardant put on the tree to stop it being destroyed by the bushfire.

Centurion, which last year surpassed the 100-metre mark and is Australia's tallest tree, survived the blaze.

