I'M CRAWLING ON MY HANDS AND KNEES through a labyrinth of limbs when it occurs to me that, a hundred years ago, this was one of the haunts of the Tasmanian tiger. Also known as a thylacine, the striped, doglike, carnivorous marsupial would slip through this mixed old-growth forest, impenetrable for an upright human. It would crouch motionless beneath the 20-foot fronds of tree ferns, eyes glued to a wallaby. Six feet from nose to tail, two feet at the shoulders, 65 pounds of muscle, the Tasmanian tiger was cunning and shy, with a keen sense of smell and remarkable stamina, pursuing its prey until the quarry was exhausted.
I'm hunting, too. I've come to the inconceivably dense northern slope of the Styx River Valley, on the heart-shaped island of Tasmania, to find the tallest hardwood tree in the world, the Eucalyptus regnans, or swamp gum. The tallest such tree towers to 321 feet here in the Styx Valley, just two hours west of the capital, Hobart. (The most massive trees of all, California's redwoods, top out at about 375 feet.) In Greek mythology, the River Styx is the boundary that separates the land of the living from the land of the dead.
"We'll have to take off our packs to go any farther," says Matt Dalziel, my fleet-footed Aussie partner. It's the first day of our four-day trek through the valley, and already the undergrowth is so thick we can barely squeeze through. Matt disappears into the sylvan maze.
We're not on a trail. There is no trail. Beyond the thicket we come upon what we've taken to calling a "gangplank"a downed tree so enormous it creates an elevated walkway through the forest. We clamber atop the behemoth and move along its mossy back.
"Check 'er out, mate," shouts Matt, pointing toward the sky. "Now that's a rippah!" Nearby is a tree of magnificent proportions. Spotting this primordial creature that has somehow survived out here on the edge of the earth is like catching sight of a dinosaur. We stride to the end of the gangplank and jump back into the ocean of green. Waves of foliage close over our heads as we half walk, half swim toward the giant.
"Who knows what you'll find out there!" exclaimed Geoff Law, campaign coordinator for Tasmania's Wilderness Society, as he spread out the maps in his Hobart office three days ago. Law, 47, a dogged, inexhaustible environmentalist, has been fighting full-time for 20 years to protect Tasmania's wildlands. In the process, he's hiked more of the Styx than anyone. "To my knowledge, no human has actually done what you intend to do: cross end to end through one of the last contiguous stands of giant old-growth regnans." Then his voice caught. "Now's the time to go: It soon could be gone forever."
When I find Matt, he's standing beside a buttress root taller than he is. It would take eight people holding hands to circle the base of the trunk. I crane my head back and stare. The mammoth tree, one of the tallest flowering plants alive, shoots up and up and up, disappearing into the sky like Jack's beanstalk.