Photographing 'world's biggest blue gum' to shine light on 500yo giant in logging coupe

Deep in the forests of southern Tasmania stands a 500-year-old giant.

The tree — considered to be the world's biggest known remaining blue gum — is named Lathamus Keep for its role as a stronghold for the endangered swift parrot or Lathamus discolor. 

This Tasmanian blue gum, Eucalyptus globulus, was discovered by giant-tree hunters in the Huon Valley in 2021 in an area of forest slated for logging.

Now, after a three-month-long photo shoot, a portrait of the tree has been launched at Hobart's Wild Island Gallery.

Photographer and tree conservationist Steven Pearce, along with his partner and canopy ecologist Jennifer Sanger, are trying to raise awareness of Tasmania's giants.

"You can tell someone that a tree is 80 metres tall, and you know, that person can have an understanding that that's a big tree," Dr Sanger says.

"But if you actually show people it via a photo, actually how big these trees are, you can really get a full appreciation of how special these forests are.

Of the giant trees Mr Pearce and Dr Sanger have photographed around the world, Lathamus Keep is the only one living in an unprotected forest.

The forest's manager has a policy to protect verified giant trees, but there are concerns about the blue gum's future.

"Its image is telling a very important story," Dr Sanger says.

Giant-tree discovery

Despite being a landmark tree, Lathamus Keep was only found in 2021 by giant-tree hunters Jan Corigliano and Carl Hansen.

"I'd been doing all this mapping stuff that was based around using [remote sensing] data," says Mr Corigliano, who is also an engineer.

Analysing this data for the Huon Valley allowed the pair to identify 20 trees, or "hits" in the area that were likely to be giants, including one particularly promising one.

"It was a good-looking hit … [the tree] was quite tall and had a really big crown," Mr Corigliano says.

To verify the data, the pair visited the forest in the Huon Valley one rainy November day last year.

Using GPS they navigated their way through the undergrowth to each hit, including the tree later called Lathamus Keep.

"There aren't any other particularly big ones left."

Biggest trunk, biggest tree

Verifying that Lathamus Keep was a giant tree was a long process with many steps, Dr Sanger says.

These included measuring the tree's girth, measuring its height by climbing to the top with a tape measure and using these measurements to calculate its volume.

State government-owned forest manager Sustainable Timber Tasmania (STT) defines giant trees as "at least 85 metres tall or at least 280m³ in volume".

Lathamus Keep's calculated trunk volume came in at 325m³, making it not only a giant tree, but the biggest blue gum in the world, according to Dr Sanger.

A specialist in Australian giant trees, Brett Mifsud, confirms it is the biggest known remaining blue gum and estimates it to be 500 years old.

Mr Mifsud, who has been climbing and researching giant trees in Victoria and Tasmania for 30 years, says Lathamus Keep is, by some distance, the last of "an elite class" of blue gum.

A tree's volume is considered by scientists to be the best measure of its size, Dr Sanger says.

"We measure trees by wood volume and we have done for ages," Mr Mifsud says.

Mr Mifsud explains that California's General Sherman — a giant sequoia that is famously the world's biggest tree — is given this title because its trunk contains more wood than any other on Earth.

It was Lathamus Keep's status as the world's biggest blue gum that nudged Mr Pearce and Dr Sanger across the line in deciding to take its portrait.

How to photograph a giant tree

Mr Pearce says photographing a giant tree is inherently problematic.

"The biggest challenge … is the fact that it's 80m tall," he says.

"Generally, cameras don't really work super well at capturing something that's so large.

"What we do is actually set up a camera system that can travel the height of the tree."

This was accomplished across five separate trips to the forest and with help from volunteers.

Then it was a matter of waiting for the right weather.

"You're just there, in the silence of a bitterly cold morning, looking up at this tree, seeing the subtle sunshine coming through the fog.

"It's unbelievable."

The Grove of Giants

The finished portrait of Lathamus Keep comprises about 80 different photos that are stitched together digitally.

It also includes the people involved in its measurement.

Dr Sanger says that of the 11 giant-tree portraits she and Mr Pearce have taken around the globe, this one is the most important.

This is partly because, according to Dr Sanger, Lathamus Keep is living in a coupe that was scheduled to be logged by STT in 2023.

The coupe has about 150 trees with diameters over 4 metres, Dr Sanger says, and Mr Mifsud confirms that at least four of these trees are verified as giants.

It was the coupe's large number of big trees that led Dr Sanger and Mr Pearce to name it the Grove of Giants.

"What makes it really special … is that there are giant trees from four different species of eucalypt tree," Dr Sanger says.

"It's probably the only place in Australia where you can find [that]."

Dr Sanger explains that the coupe, known as DN007B by STT, contains Tasmania's "best remaining patch of old-growth blue gum forest", which is important habitat for the critically endangered swift parrot.

She says this type of forest is also one of the most carbon-dense on the planet.

The importance of the Grove of Giants for all these reasons inspired Dr Sanger and Mr Pearce to begin a campaign to raise public awareness in the hope of preventing its deforestation.

What is the forest giant's future?

STT's general manager for conservation and land management Suzette Weeding says the organisation will protect a tree that has been verified as giant.

"Giant trees hold important cultural, societal, and carbon values," she says.

"Sustainable Timber Tasmania actively retains an ongoing commitment to protect its forest giants.

"During 2021/22, several giant trees were identified, managed, and protected across Tasmania in accordance with STT's giant tree policy."

Ms Weeding says coupe DN007B is not scheduled for harvesting in 2023.

According to STT's current Three Year Wood Production Plan, the coupe may be harvested before July 2025.

In response, Dr Sanger and Mr Pearce note that STT "very recently" removed DN007B from its list of coupes to harvest in 2023.

According to Mr Mifsud, STT's approach to protecting giant trees by logging the forest around them save for a buffer zone is a "ridiculous and failed method of tree protection".

He says the remaining giants suffer increased wind damage, drying out, dieback, and risk of destruction by fire.

Ms Weeding says 100m-radius protection zones are designed to take into account the risk of fire or wind damage.

Mr Mifsud argues that STT's continuation to log old-growth forest, regardless of whether it contains giant trees like Lathamus Keep, demonstrates a "1940s mindset".