The tallest tree

In 2015, Brett Mifsud received some curious information from a contact at VicForests: a map of a heavily forested area 80 kilometres east of Melbourne that showed some unexpected altitude readings. Mifsud knew this region well – any spare moment he would head there in his late-model Subaru, which was scattered with GPS devices, rangefinders, tape measures and a dog-eared spiral-bound notebook thick with scribbles. His main aim on such excursions was to find, and register, large specimens of Eucalyptus regnans. These trees, more commonly known as mountain ash, are impressive when they reach typical heights, but when they grow even taller they can evoke the kind of gasp usually saved for Gothic cathedrals. Over the years Mifsud had found numerous massive mountain ash trees, and by registering their presence with VicForests he affected what loggers could and could not touch in the vicinity. His research contributed to VicForests’ development of a protection plan, which excludes core areas of large trees from harvest and regeneration burns. But, “if anything,” Mifsud says, “letting people know about these trees is like saying, ‘Stop. Look! If these trees exist, then so does a rich ecosystem down to the micro level.’”

The map that Mifsud had obtained featured information that was impossible to acquire from the forest floor, and wasn’t evident on any other cartography. It had been created using Light Detection and Ranging (LiDAR) technology, whereby a low-flying plane sent out laser pulses across the terrain below to capture infinitesimal changes in altitude, from the mulchcaked ground to the fresh green shoots atop the canopy.

Some of the height variations shown on the map made Mifsud pretty frisky, but frisky for him is an unsurprising state. The 49-year-old is bone lean, and can be as jittery as the teenagers he teaches at a suburban high school. Over the past two decades he has climbed trees in Borneo and the Pacific Northwest, co-written papers with such snappy titles as ‘Observations of Spencer’s Skink Pseudemoia spenceri From Within the High Canopy of an Overmature Mountain Ash Eucalyptus regnans’, and “roped up” science celebrity Brian Cox so that the foppish Mancunian could swing high from a tree and get that in situ hero shot.

Mifsud has also led numerous excursions into the proposed Great Forest National Park, which would add more than 350,000 hectares to the 170,000-hectare patchwork of forested areas scattered in an arc from the north-east to the south-east of Melbourne. Those who have accompanied Mifsud to the park-in-progress include the then federal environment minister, Mark Butler, who was driven down a rutted road in a Comcar so that he could make an on-the-stump speech, and Jeff Shapiro, a famous (in certain circles) global adventure athlete who plans to promote the park, as he stated in his Montanan drawl, “by wingsuiting out of a hot air balloon and landing in a mountain ash like a sugar glider”.

Mifsud’s trip into the forest would be more sedate. With the LiDAR map on the back seat, he drove to the region with the windows down, the smell of Eucalyptus cypellocarpa overriding the car’s usual whiff of damp polyester fleece. The map took him to a logging coupe. All was quiet on a Sunday, no one in hi-vis eyeballing him as he skirted the clearing. Kubota excavators stood idle, resembling museum-display dinosaurs.

From the clearing, Mifsud dropped, as the LiDAR map suggested, into a valley. Stands of grey gum gave way to blackwood, myrtle beech and unspooling bracken fiddleheads. A crop of wire grass not only slowed his progress but also left angry grazes. Mifsud described the terrain at a microbotanical level. “Oh, Persoonia arborea! How cool is that!” He crossed a clearwater stream framed by “a forest of epiphytes” and scrambled up the other side. Mifsud’s monologue gathered pace, but he fell silent when he looked up to the canopy. He then lurched from side to side as a gorilla might. To most people, a tall tree is a tall tree, but by eye alone – and some lurching – Mifsud could tell that the top of one particular tree was that much higher.

“Oh, oh, oh,” he muttered in a rare moment of being lost for words, while he rummaged in his backpack for a TruPulse 200L laser rangefinder and a button-laden calculator. The mountain ash in his sights had a trunk that, 20 metres from the base, divided into two branches. The one on the right bowed slightly, but the one on the left was pencil straight.

“That’s gotta be clocking 80, easy,” Mifsud said, almost to himself, as he set the rangefinder. And then, “Oh, oh … 87 metres, 87 metres!”

There was a time when one could find mountain ash trees that topped 100 metres. In Thorpdale, Gippsland, a sign directs tourists to the “site of world’s tallest tree”. Anyone taking the detour will be met with a view to rolling dairy country – the “site” – as the tree was felled in 1884 by local farmer Bill Cornthwaite, and then measured to be 114.3 metres by Bill’s brother, George, a government surveyor. Due to the 2009 bushfires and more than a century of logging, the possibility of a mountain ash reaching beyond 85 metres

undetected has become extremely rare. Mifsud was certain that, in the valley east of Melbourne that day, at 87.6 metres, he had just found the tallest tree on the Australian mainland.

After making a few notebook scribbles Mifsud headed back to the car, again skirting the corral of banana-yellow machinery. The proximity of the logging coupe was worrisome, and this wasn’t the only danger for the tree: the point where its trunk forked was starting to split, and then there was always the threat of bushfire. Even if a fire didn’t bash through the region like it had eight years ago, it wouldn’t take much for this mountain ash to burn. Call it nominative determinism. But that day, back at the car, Mifsud chose to forget the threats. He savoured the fact that he’d located a still-standing giant, and then spent a quarter hour extracting leeches from his Explorer socks.