The vibration of the big Pratt and Whitney came up through the jump seat, churned through the scrambled eggs in my stomach, and settled in the fillings of my teeth like a bumblebee in a peanut butter jar. DeHaviland built the Beaver to take off from a patch of water not much bigger than a hot tub, to stay in the air when even a migrating goose is grounded, to fly impossible loads into impenetrable country. It is the quintessential bush plane.

For all that, the designers figured, most backcountry air travelers are willing to make certain sacrifices in comfort. There was no point trying to talk to the rest of the passengers over the roar of the engine, so I put my nose against the window and watched the forest slide by below.

I've spent a fair amount of time flying over wilderness in the Rocky Mountain West, and I've decided I don't like the bird's-eye view. A plane makes big country seem very small. I've looked down on jagged ridges and spruce tangles that took me a week to walk through only to realize that the motor homes and tourist traps were never more than ten or 15 miles away. Wyoming has the most remote wilderness in the Lower 48, and even there, you're never more than 38 miles from a road.

But this was not Wyoming. This was northern Saskatchewan, and the tangle of trees and water below was part of North America's great boreal forest, 2.3-million square miles of timber stretching from the Bering Sea to the rock-bound coast of Newfoundland. The conifers stretched to the horizon in every direction, and the more we flew, the more we saw. The size of the place was beyond imagining.

The processes at work down below operated at a scale worthy of the landscape. As we flew on, I saw the scars of old forest fires, and the sky was hazy and tan with smoke. Out of sight to the west, a fire was in the process of consuming several hundred thousand acres of spruce and jack pine, a cataclysm forestry officials were powerless to stop. The ecological forces in play were invisible from the air, but they were, if anything, even more far-reaching than wildfire, stretching out down the migratory corridors of the New World to touch the tropics and grasslands of Patagonia far to the south.

It's been estimated that 300 species of birds pass the long days of the northern summer in America's boreal forest. Ninety-six of these species depend on this system as a nursery--more than half the breeding populations of these birds nest in the boreal forest. Birds as tiny as the bay-breasted warbler and pine siskin, as imposing as the whooping crane and trumpeter swan, raise their families here.

And it's a great place for ducks. Thirty-percent of the boreal forest is covered with water, bogs, fens, marshes, lakes, and rivers that provide pristine nesting habitat for many species of North American waterfowl. Last summer, 87-percent of our buffleheads nested in the boreal forest.