While Our Backs Are Turned

Petersham, Massachusetts, my home for the past six years, hasn’t changed much since the early 1900s. If anything, the place has grown more tree-filled and sedate. A small rural town of twelve hundred people, it’s too far from Boston to accommodate commuters, and strict zoning statutes limit new construction to six houses per year. We don’t have a gas station or stoplights. It’s inexpensive to live here; homes purchased in the past year averaged just over $150,000. I’m not saying this to romanticize the place; economically, Petersham is not in its heyday.

What we do have are rich forests, streams, and the kind of ponds you can dive into. The majority of our land is permanently conserved by state agencies, nonprofit organizations, land trusts, and the Harvard Forest, a 3,700-acre research site and department of Harvard University, where I work. A large percentage of Petersham’s land base forms the shore of metro Boston’s water supply. The land’s future here is certain: bean counters in Boston value the free, 24 /7 water-cleaning infrastructure the undeveloped forest provides.

Like most of the Northeast, our landscape is blanketed by swaths of young to middle-aged oak, maple, birch, and white pine. Most of the trees are less than one hundred fifty years old—a byproduct of centuries of exploitative European settlement. Interspersed among those bright young forests are the older, darker hemlocks, which grow in thick patches where colonial farmers’ wood-lots once stood.

Even if you don’t spend much time with trees, even with your eyes closed, you’re aware when you enter a hemlock forest that you’ve arrived someplace new. It’s ten degrees cooler than surrounding forests, for one thing, because of the dense shade: only 1 percent of the sun above an intact hemlock canopy reaches the ground at your feet. The ground itself feels different too—springier. Unlike the leaves of hard-wood trees, which decompose within a few years, a mat of hemlock needles can be more than a foot thick, gradually decomposing over hundreds of years. The air pockets between the needles are like a natural trampoline.

A hemlock grove is so shady that it’s really only other hemlocks that can thrive in the understory. The rich greens and browns of hemlocks of all sizes stretch as far as you can see, punctuated by the occasional broad leaves and flowers of mountain laurel and hobblebush. Vibrant orange newts scramble around in the moist soil, navigating tiny thickets of wintergreen and brilliant red partridgeberry.

The few moose I have encountered in the forest have been standing among hemlocks, in the shade that helps keep their massive bodies cool. Many other creatures—black bear, bobcat, fisher, porcupine—move through the trees as well. Petersham’s streams and rivers are sheltered by hemlock branches, which keep the waters cool for sensitive species like trout, and for the anglers who pursue them up riverbeds in all seasons. And in contrast to broadleaf trees, which guzzle water from streams, hemlocks only use as much water as their thin, efficient needles require. Throughout the year, layers upon layers of hemlock branches intercept moisture and sound from the air, making everything calm, quiet, and green.

Which brings me to the birds that also call this place home.

In the slowed-down quiet of life in Petersham, I’ve gotten to know the comings and goings of warblers and waxwings, woodcocks and geese. Spring draws their fervent arrival, and in October they take their leave. Among the last birds to hit the road before winter are the black-throated green warblers. Their bright yellow heads and chipper zoo-zee calls disappear from hemlock boughs all at once in late fall. I don’t blame them for going. Winter can be mean around here.

Come March, they’ll swoop back over three thousand miles, from whichever Central American clime where they’ve spent the winter scouting bugs. And once they get back to Petersham in May, they’ll...