By Thomas W. Franck

If a Tree Falls: Fighting Climate Change in the Harvard Forest

More than a century old, the Harvard Forest still bears traces of its past—stone fences, ancient oaks. Yet changes have come, too, subtle but significant.
By Bailey M. Trela

Heading west out of Boston along Route 2 will take you—eventually, when the mingled sights of wood and water by the roadside have just begun to bore—to the town of Petersham, Mass., home to the Harvard Forest.

The forest’s main entrance, a sloping driveway that leads up to a long brick building housing administrative facilities and a museum, stands like a bulwark before the rambling mass of the woods. Paths broad and thin lead outward, along curt fields and by white colonial homes that shelter researchers and students.

I arrive early one day—the researcher I’ve arranged to meet is still an hour out—and go for a walk with Tom, the photographer. The path we choose is broad, of tamped earth. We pass a group of students from Quincy House on a weekend outing, shooting bows and arrows at nothing by a maple syrup distillery, its planed pine siding gray with age. Turning, we walk by a sawmill; gargantuan stacks of logs, their severed ends patchy-white with the drippings of their sap, rest deeply in the grass. In front of the mill, arranged in geometrical ranks, a fleet of solar panels face the sky.

The path we follow is deep-set, traced and trod endlessly. It’s a cold day, and the muddy divots that dot the road are edged with frost. A golden streak of dribbled sawdust occasionally enlivens the center of the path. Wiry palisades of weed and bush jut out from the verge. Strips of birch bark, white as bandages, stipple the path. More than a century old, the Harvard Forest still bears traces of its past—stone fences, ancient oaks. Yet changes have come, too, subtle but significant. In the past few decades, the forest has come to play host to invasive species and parasites, like garlic mustard, the wooly adelgid, and southern pine beetles. Its growing seasons have lengthened, and its average temperatures have increased. The hemlocks are dying, and new, thinner growth has only recently begun to fill the voids left by fires.

The Harvard Forest encompasses over 3,000 acres of rural Massachusetts in the town of Petersham. As a center for biological research, various long-term experiments continue to help scientists understand the effects of climate change over the decades.
The Harvard Forest encompasses over 3,000 acres of rural Massachusetts in the town of Petersham. As a center for biological research, various long-term experiments continue to help scientists understand the effects of climate change over the decades. By Thomas W. Franck

Then, there are the traces of the researchers studying these changes: the solar panels, the neon ribbons that denote foliage, the occasional humming metal box that funnels electricity to stations throughout the woods. A few weeks from now, the forest will be crowded. Researchers will arrive from all over the world, mingling with graduate students, undergraduates, daytrippers, hikers, and nature enthusiasts; they will note the effects of climate change in the forest and attempt to make sense of them.

But the woods are very quiet now. Only the sound of a chickadee and its drooping, half-step cry. Out of nowhere, walking toward us, we spy two women, middle-aged. They signal us and ask if we’re coming from the road.


As far as its mission is concerned, the Harvard Forest has changed little during its 100-year existence. Founded in 1907 as a research and field laboratory for students and as a model of sustainable forestry, the forest continues to fulfill these aims. Today, students can research at the forest over the summer, and many groups, like the students in Quincy, visit for short trips.

“The goal was always to be a remote part of Harvard that could fully immerse students and faculty in the New England landscape,” David R. Foster, the current director of the forest, explains. “That was the intent in 1907, and that’s what it currently is as well.”

Director of the Harvard Forest David R. Foster surveys neighboring hemlock trees in one of the only areas of the forest which exists purely for observational purposes.
Director of the Harvard Forest David R. Foster surveys neighboring hemlock trees in one of the only areas of the forest which exists purely for observational purposes. By Thomas W. Franck

Foster assumed the directorship in 1990, though his relationship with the forest extends as far back as 1983, when he became an assistant professor of biology at Harvard. In his nearly 30 years as director, he hasn’t seen the forest change so much as he’s witnessed the broader research world attempting to catch up.

“In many ways, the forest was established in advance of its perfect role,” he explains. “[The founders] knew that intensive, local, long-term research was important. What’s happened in the last 30 years is that the whole globe has come to realize the same thing.”

Sights, sounds, and studies of the Harvard Forest. O'Keefe remains active in his research, documenting the growth of tree species.

This highly particular approach, grounded in a specific environ, is one that Foster has long championed. “All the [climate change] research that goes on should be really strongly grounded in local places, in very intensive local research,” he says. “You have to go into whatever landscape you’re going to be working in and realize that where you are is just one point in time, and there’s this whole flow of history that has shaped what you’re seeing. And you have to begin to explore that.”

One of the unique aspects of the New England landscape, as Foster points out, is its melding of the cultural and the natural. The Harvard Forest itself, like many forests in New England, shows evidence of its past as farmland. Centuries ago, the land was cleared for agriculture. When farms began to disappear in the middle of the 19th century, nature reclaimed the land, resulting in the forest of today, a thicket of new growth spotted with old stone fences and paths once used in farming.

While the majority of the land owned by Harvard consists of forest, other portions of the expansive property include farmland.
While the majority of the land owned by Harvard consists of forest, other portions of the expansive property include farmland. By Thomas W. Franck

The Harvard Forest’s importance to global climate change research, as it stands today, derives from its long history and extensive backlog of both natural and manmade change. “The great advantage that we have is more than 100 years of measurements and observations that we can bring to bear to understand what’s happening today,” Foster says. “When you look at long-term ecological research, there are new programs that are addressing this, and we’ve got 100 years of perspective to bring to that.”

But the forest does more than just export a particular research method. Its extensive record of scientific data aids research the world over. “With the forest, there’s a complete openness for anybody anywhere—student, public citizen, or world class scientist—to come and do research here,” Foster explains. “And no matter who you are or what you do, all of your data and information gets collected and embedded into an archive that’s available to the entire world.”

As a part of the ongoing conservation and land management effort, a fully operational sawmill harvests fallen trees within the Harvard Forest. At left, a fraction of the collected and cut wood will likely be used for heating; at right, a flatbed trailer used for carrying lumber stands idle. By Thomas W. Franck

According to former Interim Dean of the College and professor of systematic botany Donald H. Pfister, the Harvard Forest provides unique resources for researchers engaged in hurricane tracking, tower monitoring, and soil warming investigations among other types of studies. “I have several colleagues involved in cutting edge research there,” Pfister says.

* * *

Julia A. Wheeler studies the small things.

At the moment, she is kneeling by a ribboned-off plat of leaves, inspecting the lonesome sprigs of red maple that shoot up from the greater gray. She looks for bite-marks—the angled snips of deer, the furry stripping of mouse-teeth—and points them out when she finds them.

A northern white pine tree sparkles in the morning sun inside the Harvard Forest.
A northern white pine tree sparkles in the morning sun inside the Harvard Forest. By Thomas W. Franck

The maples seem a sorry sight. A foot or two in height, nearly all have been nibbled at. The color of the saplings, dense from overwintering, is unpromising, at least to the novice’s eye.

But it’s not animal browsing that worries Wheeler. With unpredictable temperatures this spring, sudden chills after sudden warmth, many plants have been tricked into budding too soon. “We’re basically here to check damage,” she says. “Because the maples were bud-swelling, ready to put out their leaves—and that’s when they become vulnerable to cold.” With some species, Wheeler explains, you could place the winter-hardened buds in liquid nitrogen, and they’d come out still alive, still waiting for warmth. It is the first attempt at growth that is a gamble, when the sensitive, striving material of buds can be killed by a frost, by a long cold night.

But for the most part, the maples seem to have weathered well. As Wheeler hops about, crouches, looks, and cradles the slender wood, she exalts: “Beautiful!” Or: “Wonderful!”

Wheeler is Canadian by birth (crooning Os crop up sporadically in her speech). She did her undergraduate work in marine ecology at Memorial University in Newfoundland before making the leap to plant ecology in Labrador. From there she went to Switzerland and took her Ph.D. at the University of Basel; she subsequently worked with the Swiss Federal Institute for Snow and Avalanche Research, studying the alpine arctic willow—a tiny thing, she says, pressing her two thumbs together: “About the size of two thumbnails.”

In stark contrast to Wheeler's alpine willows, as the oldest tree in the Harvard Forest, this blackgum tree has stood in this spot for over 420 years.
In stark contrast to Wheeler's alpine willows, as the oldest tree in the Harvard Forest, this blackgum tree has stood in this spot for over 420 years. By Thomas W. Franck

Wheeler’s work in the Harvard Forest is concerned with phenology—the measuring of climate change’s effects on annual phenomena, as budding or flowering. Beyond the red maples, she’s also here to examine a few patches of garlic mustard, an invasive species that has been present in North America for roughly 150 years. Wheeler has been studying how plants like garlic mustard have reacted to the changing climate: how fast they’ve spread in higher temperatures, for instance, and where exactly they’ve spread. In many instances, climate change might accelerate the diffusion of invasive species.

With shorter growing seasons comes an understandable danger: Plants produce fewer leaves, they photosynthesize less, and as a result less and less carbon dioxide is absorbed from the atmosphere. If a sudden cold comes on and damages emerging buds, the plant will produce fewer leaves, and the problem is exacerbated. With increasingly variable growth seasons becoming a standard reality, the interactions of native species and garlic mustard—which is poised to take advantage of shorter growing windows—need to be understood.

The SWAN (Soil Warming and Nitrogen) plots are a set of 24 three-by-three meter plots engaged in what’s known as a factorial field experiment—essentially, the interactions of multiple elements are examined in conjunction with one another. Some of the plots have been dosed with extra nitrogen; others are warmed an extra five degrees Celsius by buried cables; the red maples and garlic mustard share their ground with other plant life, even, in a few plots, colonies of ants, as small flags stuck in the ground make clear.

Crouching down, Wheeler brushes back a mat of leaves and points to a purplish burst of leafage: a tuft of garlic mustard, its tendrils shriveled-looking, its leaves clearly veined. It seems an insignificant blot in the matte mass of leaves, but, as Wheeler explains, it’s a clever plant, and well-equipped to harm its neighbors. Like all good invasive species, garlic mustard comes equipped with sundry unfair advantages. It’s capable of photosynthesizing during the winter, which allows it to get a head start when the growth season begins in earnest; it couples this precocity with the deployment of phytochemicals, which it pushes out through its roots, that inhibit the ability of nearby plants to absorb water and nutrients.

Though the experiment may seem small-scale or picayune, Wheeler insists that it’s unique, a project only possible in a research institution like the Harvard Forest. “It’s the sort you can only set up when you have the infrastructure available for it,” she says. “You need water; you need electricity—it just makes things logistically simpler when you have a very nice field research system.” In addition to the boon of material resources, Wheeler cites the forest’s community as a key resource—in the summertime, undergraduates and researchers come from all over the world to work and study.

Known for their curling, white bark, white birch trees are often cultivated for their ornamental qualities. Due to their heat intolerance, white birches can often be found in cooler geographical regions.
Known for their curling, white bark, white birch trees are often cultivated for their ornamental qualities. Due to their heat intolerance, white birches can often be found in cooler geographical regions. By Thomas W. Franck

One of those researchers, Anne Pringle, who is currently an associate professor of botany and bacteriology at the University of Wisconsin-Madison, points out that not all invasive species are necessarily dangerous—besides, they provide good models of research for changes in biodiversity, in landscapes, and in the movement of species across environs. She notes, though, that garlic mustard does not fall into this gray area. It’s particularly dangerous, she says, because it has “the potential to disrupt natural environments and plant growth.”

As we exit the SWAN plots, Wheeler seems to be a in a good mood (cries of “Ah, poor maples!” were heard only sparingly). She looks up at the trees and gives us a reminder: “The stuff I tend to work on is very low to the ground,” she says. “But in plant ecology you can work on a lot of different levels.”

“The scale I have to think on is so small,” she says, before pointing up: “It’s easier to work when you don’t have to climb up there.”

* * *

For decades now, John F. O’Keefe ’67 has kept to the same path.

Every four or five days in the springtime, he comes out to the forest and notes the status of buds. His trees, scattered along a rambling path through the woods, are marked with pink and black flagging. He looks for leaf-out, his chosen signifier of growth.

With his tan winter cap, clean white beard above silver-lined spectacles, and earthen-hued jacket and pants, O’Keefe resembles a gnome ambling through the alternating sunlight of the forest. Since 1990, he has annually observed many of the same trees. Some, of course, have died. When this happens, O’Keefe replaces them with similarly situated specimens, under the guiding philosophy that, for many intents and purposes, a tree is a tree. He has gradually stockpiled a long-term dataset that acts as a sort of backbone to other research taking place in the forest.

Normally, O’Keefe would not start making visits to the forest until early April. This year, he made a few trips in late March because the winter had been mild, but when a cold snap hit he postponed the rest of his planned visits. “What I think that weather points out,” he says, “is that what climate change really means is more extremes.” Though this past year was the warmest on record worldwide, O’Keefe explains, “What we’re also seeing is more variability.”

O’Keefe’s phenological observation work with buds underscores general trends in the forest. Though damaged buds mean a plant will likely take up less carbon dioxide during the growth season, O’Keefe has actually seen earlier springs with the passing years, and lengthening growth seasons, in which plants are removing increasingly more carbon dioxide from the atmosphere. While this may seem at first blush like a benefit, it introduces new problems, among them the availability of other resources necessary for growth, like water. In addition, it’s unclear how different species will react to longer growth seasons and earlier springs—a delicate balance might be upset.

In essence, O’Keefe’s notes provide a grounding in particulars, a reference log that helps corroborate, complicate, or make real the claims and research of other scientists in the forest. Nowadays, he continues his observations under contract for OEB professor Andrew Richardson, who works with phenocams—cameras, set about the woods, that track leaf canopy development. As O’Keefe explains, his notes provide another way of looking at data; they are malleable; they could almost contribute to any project. It’s difficult to say how his observations will be used in the future. The important thing is to keep recording.

O’Keefe’s extended observations speak to a great strength of the forest as a research resource—research projects within the forest have a long history, the backlogs of data are extensive, and this extension is understandably critical when one attempts to draw conclusions about long-term developments. “It’s probably one of the better ways to track the plant community’s response to climate change,” he says of his own observations. “It’s such a variable from year to year—with all that annual weather noise—you need a really long-term dataset to actually track any climate signal.”

O’Keefe’s metric is simple. He checks the progress of leaf growth, and when 50 percent of the leaves have come out, he marks it down. While other researchers might parse phenophases, O’Keefe believes that full leaf emergence is the most useful and important data point to track.

His observation walk is ponderous. O’Keefe stops abruptly to inspect nondescript wayside foliage and jot notes down on a datasheet, then he moves a few feet forward and repeats the process. Every now and then he cants back his head and raises a pair of neck-slung binoculars to his eyes and attempts to discern, against the noontime sun, tiny buds wavering 50 feet above. He looks up nowadays because he once looked down.

At Harvard College, O’Keefe concentrated, because he didn’t want to concentrate in anything at all, in the now defunct catch-all subject of Social Relations. After spending two years with the Peace Corps in Lesotho, he returned to an America still embroiled in the Vietnam War. He joined the Massachusetts Air National Guard and spent six years as a pilot.

“What got me interested in forest ecology was flying over New England, looking down and it’s all forest—well, it got me intrigued.” He began to take ecology courses through the Harvard Extension School, moved on to graduate school, and eventually ended up as Director of the Harvard Forest’s Fischer Museum.

Though his email signature clearly identifies him as retired, he stumbles every now and then, describing his current state of employment as something more like semi-retirement. In many ways, O’Keefe seems habit-bound. Though the construction of an upstream weir several years ago has made stream observations essentially unnecessary, O’Keefe continues to take notes on flow rates, on obstructions. “It’s something I got used to doing,” he says, “so I just keep it up.” He takes a pleasure in seeing, in noting the forest’s myriad subtle tells. For instance: “When the leaves emerge on the trees, and they start drawing up water, you see a drop in the flow of streams.”

Everything catches his eye. Behind his glasses, a refined form of vision is at work. He identifies endlessly: Here is shadbush. White birch. Witch-hazel. When I absentmindedly remove a fork of needles from a bush, he notices and calls out, “Red pine,” because the needles of that tree, tellingly, grow in pairs. With time spent in the woods has come sight, or a new form of it.

“Having done this for 27 years, you get to observe things pretty closely,” O’Keefe says. “You learn a lot just from that, and just by walking the same loop again. You notice subtle changes that would otherwise go by you.” As if to prove his point, he directs my attention to a small rug of mayflowers—a splash of green and little more—in which are hidden soft, shadowed blue blooms that give off a briskly sweet scent. “It’s really unobtrusive. I probably didn’t notice it for the first five or six years,” he laughs, before continuing: “And then I did.”

O’Keefe’s steady output has become more and more important: “In 1990, I don’t think he anticipated the significance his work would have,” says Plotkin. “I think in the past few years its importance has really blossomed.”

At a certain point we take a left off the main road and enter into an older section of the forest, one that’s now been closed to ordinary hikers, because the hemlocks that populate it have been beset by a parasite, and the fear is that they might fall suddenly, dangerously. O’Keefe flips a hemlock frond and points out, clustered on the bottom of the leaves, a close-set grouping of cottonous white dots. Inside these cocoons wooly adelgids—a type of aphid—are draining the hemlock’s sap.

But as O’Keefe points out, most of the trunks that crisscross the path are natural deadfall; the adelgids have yet to wreak too much havoc. Yet this part of the woods still feels senescent, vaguely insidious. It is noticeably cooler beneath the spray-like leafage of the hemlocks, the air still with a finger-numbing chill. The path is humped with moss-shrouded roots and stones, and the sinister limbs of the hemlocks—sliding out horizontally from the trunks, so that it seems they are foreign boughs that have impaled the tree—dominate the view.

Before we leave him to the rest of his walk, O’Keefe brings us to a hollow in the hemlocks which shelters a still pool, above which presides a toppled tree. He points to the center of the water: “Do you see those grayish blots?” Beneath the green glass surface of the pool we can make out a cluster of milky globes. “I suspect those are wood frog eggs,” O’Keefe says.

“Gosh they’re loud at night,” he goes on, laughing. “It sounds just like ducks quacking.”

* * *

The early spring is a strange time to visit the Harvard Forest. As we leave it on a Wednesday, the parking lot is empty beneath a chilled gray sky. Fields of grass are still crisp and matted beyond the post-and-rail fences that gird them; the light green fronds barely turn in the cool wind.

With the welter of summertime research still a few weeks off, the plants are beginning their slow emergence into life, preparing for the work of growth, while projects stir from their own hibernations.

There are variables yet. The transition into warmer weather has become in recent years a bit of a toddle. Impracticable fluctuations slow the progress of projects that are in turn meant to investigate these changes.

But the researchers remain, gathering their data and storing it. They take notes and simply look, discovering more about the forest, in the grandest and smallest scales. Even with 100 years of research behind them, the changing never ends, and there’s still plenty more to learn.

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