On a cool morning in the winter of 2011, Dennis Cronin parked his truck by the side of a dirt logging road, laced up his spike-soled caulk boots, put on his red cargo vest and orange hard hat, and stepped into the trees.

He had a job to do: walk a stand of old-growth forest and flag it for clearcutting.

In many ways, this patch of forest was unremarkable. Cronin had spent four decades traipsing through tens of thousands of similar hectares of lush British Columbia rainforest, and had stood under hundreds of giant, ancient trees. Over his career in the Canadian logging industry, he had seen the seemingly inexhaustible resource of big timber continue to dwindle, and the unbroken evergreen that once covered Vancouver Island reduced to rare and isolated groves.

The cutblock represented a small sliver – around the size of 12 football fields – of the kind of old-growth forest that once spanned the island nearly from tip to tip and coast to coast. But this small patch of trees was a prime example of an endangered ecosystem. Black bears and elk, wolves and cougars passed quietly under its canopy. Red-capped woodpeckers knocked on standing deadwood; squirrels and chipmunks nibbled on cones to extract seeds; and fungi the size of dinner plates protruded from the trunks of some of the largest trees in the world.

As a forest engineer, Cronin’s job involved taking stock of the timber, and producing a map for the fallers to follow. At regular intervals of a couple dozen metres or so, he reached into his vest pocket for a roll of neon orange plastic ribbon and tore off a strip. The colour had to be bright to catch the eye of the fallers who would follow in the weeks or months to come.

He tied the inch-wide sashes around small trees or the low-hanging branches of hemlocks or cedars to mark the edges of the cutblock.Timber companies in the province follow a forestry code stipulating that forest engineers must leave an intact buffer of 50 metres of forest up from a river, especially one that is known to be a spawning ground for salmon. Some engineers keep tight to those regulations to try to extract as much timber as possible from a given area. Known as “timber pigs”, they work the bush under a singular mantra: log it, burn it, pave it. The sentiment is twofold: ecology is secondary to economics, and these forests exist to be harvested.

But Cronin was often generous with these buffer zones, leaving 60 to 75 metres – as much as he could without drawing the ire of co-workers or bosses.

Once the boundary of the 12 hectares was flagged with orange ribbon, Cronin crisscrossed the cut-block, surveying the pitches and gradients of the land, and marked a direct line through the forest with strips off another roll of ribbon, this one hot pink. He traversed any creek he came across and flagged it with red ribbon. When the flagging was done, the green-and-brown grove was lit up with flashes of foreign colour.

As Cronin waded through the thigh-high undergrowth, something caught his eye: a Douglas fir, larger than the rest, with a trunk so wide he could have hidden his truck behind it. He scrambled up the mound of sloughed bark and dead needles that had accumulated around the base of the giant tree.

Dennis Cronin looked up.

Facebook Twitter Pinterest Big Lonely Doug, one of Canada’s tallest tree. Photograph: TJ Watt / House of Anansi

The tree dominated the forest – a monarch of its species. Its crown of dark green, glossy needles flitted in the breeze well above the canopy of the forest. Like many of the oldest Douglas firs he had come across in his career, the tree’s trunk was limbless until a great height. The species often loses the lower branches that grow in the shadow of the forest’s canopy. Many of these large and old Douglas firs have clear marks of disease, with trunks that are twisted and gnarled. This tree’s trunk sported few knots and a grain that appeared straight: it was a wonderful specimen of timber, Cronin thought.

With his hand-held hypsometer, a device to measure a standing tree’s height using a triangulation of measurements, Cronin took readings from the base and the top of the tree and estimated its stature at approximately 70 metres – around the height of a 20-storey apartment building. Using a tape, he measured the tree’s circumference at 11.91 metres, and calculated the diameter to be 3.79 metres; if felled and loaded on to a train, the log would be wider than an oil tank car. The tree appeared just shy of the Red Creek Fir, the largest Douglas fir in the world, located a couple of valleys away.

Cronin didn’t know it then, but he had not only stumbled upon one of the largest trees he had ever seen in his career – he had found one of the largest trees in the country. It was surely ancient as well, Cronin knew. A Douglas fir of such height and girth, growing in a wet valley bottom on Vancouver Island, could easily prove half a millennium in age. But to the experienced forester, this one looked much older. A thousand years? he wondered.

The logger could have moved on. He could have brushed his broad shoulders past yet another broad trunk and continued through the forest, leaving the giant fir to its fate. He could have walked through the undergrowth, across log and stream, to finish the job of mapping and flagging the cutblock. Fallers would have arrived; the tree would have been brought down in a thunderclap heard kilometres away, hauled from the valley, loaded on to logging trucks, and taken to a mill to be broken down into its most useful and most valuable parts.

Over 40 years working on timber hauling crews and as a forest engineer, Cronin had accrued countless days working in the forests of Vancouver Island – he had encountered thousands of enormous trees over his career. But under this one, he lingered.

Instead of moving on, Cronin reached into his vest pocket for a ribbon he rarely used, tore off a long strip, and wrapped it around the base of the Douglas fir’s trunk.

The tape wasn’t pink or orange or red but green, and along its length were the words “leave tree”.

•••

The valleys of Pacific temperate rainforest can feel both inviting and primordially ominous. There is alluring comfort among these great trees that embraces your presence and softens your footsteps. What lies beyond the curtain of mist and trees are unknowns: great treasures to be found, or great dangers lurking. One of the largest trees in the country could be hidden a few dozen metres away, obscured in the fog, but so could a bear, a cougar, or a wolf. The canopy above disappears into a grey ceiling and the forests begin to appear manageable. Everything feels within reach.

Facebook Twitter Pinterest Big Lonely Doug, one of Canada’s tallest tree. Photograph: TJ Watt/TJ Watt / House of Anansi

Less than a year after Cronin wrapped the green flagging around the big Douglas fir, the trees of cutblock 7190 were gone. Throughout the summer of 2011, the grove of old-growth forest stood awaiting its fate. When the October rains turned heavy, a sound erupted in the cool morning air: fallers, contracted by Teal Jones, were starting up their chainsaws.

Following Dennis Cronin’s ribbon markers, the fallers began bringing down the trees. The teeth of the saws bit into half-a-millennium-old trunks, casting arcs of sawdust that settled over sword fern and moss. The cut conifer quickly filled the air with a thick, woodsy perfume. The giant cedars and firs hit the forest floor with thunderous thuds, but the trees might as well have made no sound at all.

After a few months, silence returned. The fallers had long since packed up their chainsaws and gear; the trucks, laden with logs, had departed. A faint dusting of snow fell on to the clearcut. As spring came, any remaining mounds of moss and bushes of salal crackled and dried up in the unfiltered sun. Bears that had called this patch of forest home found other hollows to den, while birds sought other branches to roost. Every wiry cedar, every droopy-topped hemlock, and every great fir that once made up this rainforest grove was gone – every tree, except one.

Dennis Cronin’s big Douglas fir swayed quietly on its own in the middle of cutblock 7190. Winds swirled, grey mist rolled off the Pacific to fill the valley, and the sun rose and set. But the tree stood.

***

Along the rutted, principal logging road that ran through the Gordon river valley, environmental activist TJ Watt navigated his blue, right-side-drive Mitsubishi Delica, scanning the hills on either side through the windows.

Over the years, Watt’s expeditions to find groves untouched by commercial logging had forced him to delve deeper, along the rough backroads of the island, up mountainsides and down valleys, in search of Canada’s last great trees.

More often than not, what Watt found was not intact forests but fresh clearcuts. Driving along these roads felt like peering into a post-apocalyptic future: dry, dusty, barren – a wasteland of destruction. But every so often, at the end of a road, he found a glimpse of a glimmering and verdant past – a remnant of a forest that had been left largely undisturbed for millennia. When he spotted the telltale signs of large, ancient trees emerging from a canopy, he would park his vehicle alongside the dirt road and head into the tangled forest on foot.

With each kilometre he drove and every ramble he took, the clock kept ticking. Logging companies continued to build new roads in a feverish bid to access new groves. Watt was trying to find them before a logger did. With each expedition into the bush, he could feel the race to locate, and hopefully protect, a small fraction of the province’s arboreal legacy before it was permanently cut away. His goal was to bring back evidence not only that clearcutting old growth continues to occur, but that there are still forests that can be saved from the saw.

He had explored the valley that follows the Gordon river dozens of times, and he knew where he was going: to a patch of forest that was part of one of the largest continuous unprotected tracts of old-growth forest on the island. Located alongside the river, on a gentle slope, it was a prime candidate for producing big trees.

Out the window to his right, something caught his eye: the unmistakable orange of a fresh clearcut. He knew the road would lead to the stumps, to where he had been hoping to find trees. After turning on to a spur road he was forced to stop at a locked gate, a clear sign that there was current logging activity in the area. Watt grabbed his camera and continued on foot, across a single-lane wooden bridge. A hundred feet below, the emerald-green waters of the Gordon river thundered towards the Pacific Ocean a few kilometres away.

Farther down the road, the smell of conifer grew stronger, of cut wood and glossy needles releasing their oils into the air. He rounded a bend, glanced to his right, and stopped. The patch of old growth he had come to hike through was gone – a bite had been taken out of the forest. It was a familiar feeling for Watt, to return to photograph a lush ancient forest only to find it levelled.

Before him, this time, was a scene altogether different from any he had ever photographed. It wasn’t a forest or a clearcut; it wasn’t an unblemished ecosystem or the scarred remains of an industrial harvest, but something he had never seen.

What stood out to Watt wasn’t the fact that yet another section of old-growth forest had been decimated, but that in the middle of the cut-block a single tree remained standing. It was a Douglas fir – and it was enormous. The tree was limbless from its base to 80% of its height, where a crooked crown of branches held dark green needles that ruffled gently in the breeze. One of the branches – which bent down and then up like a flexed arm – could have been a tree in and of itself.

He brought his camera to his eye. Through the viewfinder, he framed an image unlike any he had taken before.

In the middle of the clearcut, the giant fir stood like an obelisk in a desert.

Big Lonely Doug: The Story of One of Canada’s Last Great Trees is out now