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Bringing New Life to Old-Growth Forest

August 25, 2017
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Untouched by humans for centuries but ravaged by deer and nearby development, an old-growth forest in suburban New Jersey was foundering until ecologists stepped in, revisiting the question of wilderness versus management.

You wouldn’t guess from the patchwork of yards, golf courses, and I-95 feeder roads surrounding it, but an ancient forest stands in suburban New Jersey. Sixty-five-acre Mettler’s Woods—a tiny parcel roughly one-tenth the size of New York’s Central Park—is one of the last uncut tracts along the eastern seaboard. Located 7 miles west of Rutgers University and 15 miles northeast of Princeton, its old trees, some of which predate the Revolutionary War, contain volumes of natural history. These woods hold clues to the American landscape before European settlement.

“Centuries old oaks and hickories dominate the landscape, dogwoods and mixed shrubs vie for space amongst these ancient giants,” wrote Carl D. Monk, an ecologist known for his work in eastern hardwood forests, in 1961. “Each spring, mayapples carpet the forest floor, while in the fall migratory birds rest and find refuge in the tree canopy.”

Yet Monk would barely recognize the woods today. Now part of Rutgers’ Hutcheson Memorial Forest, Mettler’s Woods does not support the plant and animal diversity it once did. The native wildflowers and birds are diminished. Few saplings take hold in the understory to replace the aging oaks. On the tail of a swift
decline, the ancient forest is dying.

“People think nature doesn’t change, but it changes fast with human influence,” says Myla Aronson, an ecology professor at Rutgers who has studied Hutcheson Memorial Forest for more than a decade.

Overgrown with invasive weeds and once overrun with white-tailed deer, Mettler’s Woods bears the ecological scars of suburban sprawl. For decades, the forest’s caretakers left the acreage largely untouched. Now, in a break with tradition, they’re fighting back. Aronson and others are optimistic the old forest can be revived before it’s too late—and that their trials may help land managers restore fragments of forest across the densely populated Northeast. A broad swath of the ecology community is waiting to see if they’re right.

***

Steven Handel gestures toward various shrubs—garlic mustard, multiflora rose, privet—as we slip from the edge of a grassy field into the trees. “Invasive, invasive, invasive,” he says.

He bends over and touches a cluster of small white and pink flowers hugging the edge of the trail. These early May bloomers are called spring beauty. Unlike many native wildflowers, which require undisturbed habitat, spring beauty can thrive in less than pristine conditions, Handel explains.

A city boy turned botanist, Handel has a soft spot for disturbed landscapes. After growing up in Queens, N.Y., he spent more than 40 years studying the ecology of urban and suburban forests and how best to preserve and restore them. He’s now the director of Hutcheson Memorial Forest and the Center for Urban Restoration Ecology at Rutgers University. Hutcheson includes the old-growth Mettler’s Woods and a 400-acre buffer of younger woods and transitional fields, where Handel is putting his ideas into action.

Definitions of “old growth” vary, but the name typically refers to a forest that hasn’t been cut or burned in several generations. In the Northeastern United States, these forests are especially rare due to extensive logging and farming by early European settlers. In Mettler’s Woods, growth rings from ancient fallen trees suggest that members of the American Indian nation known as the Lenni-Lenape, who inhabited the region until the 1750s, set fires to the forest every decade—probably to create sightlines for hunting. But it has been more than 300 years since the forest’s last clearing. A Dutch settler named Mynheer Cornelius VanLiew acquired the forest and surrounding land in 1701. He logged and farmed most of it, but a 65-acre parcel was left untouched by him and his descendents.

The benefits of these untouched forests are numerous. In heavily developed areas, in particular, fragments of old growth play an especially important role in protecting biodiversity, providing critical habitat for migratory birds and other animals and plants. Both in cities and elsewhere, the mix of old and young trees creates habitat for an array of flora and fauna, some of which may be rare or threatened. In Hutcheson Memorial Forest, for instance, researchers have catalogued more than 350 species of plants, including eight different types of oak trees and five separate species of goldenrod, and 200 species of birds, including the uncommon grasshopper sparrow and the peregrine falcon. Handel calls this rich diversity “eye-opening” for such a small, isolated woodland.

Not so different from our vegetal and avian counterparts, we humans also see perks from these woods. “In addition to their ecological benefits, such as filtering runoff and reducing urban energy use, urban trees and forests provide tremendous social benefits,” says Dave Publicover, an AMC staff scientist. “For millions of people, [urban trees] are the only daily contact with the natural world and make a major contribution to fighting nature deficit disorder.”

Along with the special role they play, urban and suburban forests come with special needs. Over the past several decades, researchers have learned that these forest fragments may require more hands-on management than their larger, nonurban counterparts—which can seem counterintuitive to the concepts of “ancient” and “untouched.” For much of the 20th century, naturalists, forest managers, and plant ecologists favored a “let alone” policy of limited human intervention, their thinking being: The natural processes that created the forest would keep it healthy and intact.

The problem with this philosophy was it didn’t account for human-induced shifts taking place outside of the forest, Handel says. “We’ve learned that it’s not enough to simply set aside a piece of land while everything around it is changing.”

***

Rutgers University acquired the land that would become Hutcheson Memorial Forest in 1955 from a local landowner, Thomas Mettler. For several decades, university stewards held on to the laissez-faire viewpoint, letting nature take its course and doing little to manage threats.

As the old farm fields that once surrounded the forest gave way to suburban backyards, and as hunters and natural predators disappeared, the white-tailed deer population exploded. Deer, in general, love the suburbs, where landscaped trees, shrubs, and other herbaceous cover provide nutritious meals and sheltered sites for birthing. By the late 1980s, an ecosystem that had historically supported two deer per square mile averaged 45 deer for the same area.

While the giant trees remained, the voracious deer drastically changed the forest understory by stripping its native wildflowers and sapling trees. This low-level denuding enabled the slow creep of hardy ornamentals from suburban backyards. Because some of these aliens weren’t appetizing to deer, the plants flourished in places, crowding out native species.

By the time Aronson surveyed the forest understory in 2003, many of the native wildflowers—mapleleaf viburnum, jack-in-the-pulpit, yellow trout lily, Solomon’s seal, wild leeks, and mayapple—had diminished or disappeared. A handful of invasives, including multiflora rose, barberry, and tree of heaven, had taken their places. Fewer plant species meant less wildlife, and overall biodiversity in the forest plummeted.

Hurricanes Irene and Sandy in 2011 and 2012 dealt further blows. Max Piana, a land manager at Hutcheson Memorial Forest and a Rutgers graduate student, estimates the storms uprooted 50 to 100 of the preserve’s oldest trees. On a recent visit, he points out a tippedover oak whose root mound extends vertically above our heads, flat like a pancake.

The death of old trees can be good for a forest. Decaying wood turns to fertile soil, which in turn creates a nursery for seedlings. The shallow ditches that form where roots separate from the ground make vernal pools, providing critical habitat for newly hatched amphibians. Gaps in the forest canopy allow young trees to grow upward. Yet in Mettler’s Woods, the absence of young oaks and hickories simply meant more space for the invasive species to spread.

Handel knew the forest needed help. The story of Mettler’s Woods was the same as that of many regional forests, decimated by a superabundance of both invasive plants and deer. If he did nothing, the old forest would be gone in a few decades. The canopy would continue to die off, and with no hardy young trees growing up to replace the old, the once-rich forest would be supplanted by an impenetrable thicket of non-native weeds. Such a landscape would be ill-equipped to serve the forest wildlife. “Our overall biodiversity, and its many values, would go way down,” Handel says.

With the help of $200,000 from a donor, Handel decided to break with convention and act.

***

In the fall of 2015, Handel oversaw the building of a 10-foot-high metal fence wrapping around the perimeter of Mettler’s Woods, protecting the old-growth forest from deer. Before a work crew finished the enclosure, a group of 90 college students walked shoulder to shoulder through the forest, driving out the herbivores.

It has been two years since the fence went up, and Aronson thinks the forest floor may be showing signs of improvement. “We’re already seeing more mayapple,” she says.

Clad in rubber boots, Aronson paces the brush with a clipboard on our recent visit. Nearby, a couple of undergraduates walk in opposite directions, pulling the ends of a measuring tape tight between two stakes. Each stake marks a patch of kneehigh, umbrella-like mayapple leaves. Aronson and her students are mapping this and other spring-blooming ephemeral wildflowers to see if the populations have grown in size since the deer were ushered out. Aronson’s student researchers will monitor these plots for the next few seasons, tracking whether the native vegetation recovers on its own, in the absence of grazers. Meanwhile, in other plots, students pull thickets of multiflora rose by hand. They’ll watch these spaces, too, to see whether native wildflowers return.

“This will help us better understand how much ecological restoration we need to do,” Aronson says. In the future, more aggressive steps could include sowing native wildflower seed in the plots, in addition to removing the invasive plants.

The researchers are using plant surveys from the 1950s, when Rutgers acquired the land, as a benchmark. “Ultimately, we’d like to return as close as possible to that historic forest understory,” Piana says. He and fellow students will measure success by the return of native species—and the ability of the forest to sustain that biodiversity.

***

What of the aging giants? A classic old-growth forest isn’t a single canopy of trees but a mosaic of life in all stages. That diversity of ages and sizes gives the forest resilience, Piana says. It may take 30 to 50 years or more for an oak seedling to join its elder siblings in the canopy. Decades of extensive decimation has created a gap in age classes, which may result in an awkward transition, Piana says. It remains to be seen how quickly the old forest will revive, or whether it will ever completely recover its original character.

To date, urban forest research has focused primarily on describing plant communities rather than on determining how those communities are changing over time. “We know from these studies that there are fewer seedlings in urban forests, there are more non-native seedlings, and often the seedlings present differ from the mature canopy trees,” Piana says. “But we don’t know why.”

Piana’s research, as well as Aronson’s and Handel’s, will help conservationists across the Northeast and beyond devise more effective management strategies for sustaining urban old-growth forest fragments. Ecologists worldwide are eager to see what recovery in Hutcheson Memorial Forest looks like and how long it takes.

As we exit the old forest, Piana and Handel meet two land managers who have come from a nearby township to check out the deer fence. They want to start a restoration project too. Like the Rutgers ecologists, they’ve seen the forest tilt sideways. They hope they can steer it back.


LEARN MORE: VISIT AN URBAN WOODS NEAR YOU

Want to see an old-growth forest close to home? Below are five other examples in the Northeast. (Maine, hit especially hard by early logging, does have some protected old-growth forest, though not in heavily populated areas.)

New York Botanical Garden (Bronx, N.Y.): The 50-acre Thain Family Forest is the largest remnant of the sprawling woods that once covered present-day New York City. It contains centuries-old oaks, tulip trees, sweetgums, and maples.

Belt Woods (Bowie, Md.): Just outside of Washington, D.C., Belt Woods contains the last stand of virgin hardwood forest on the Atlantic coastal plain. Here you’ll find examples of white oak and tulip poplar more than 3 feet in diameter.

Middlesex Fells (Malden, Medford, Melrose, Stoneham, and Winchester, Mass.): This near-north Boston plot is an old-growth forest in the making. A former mill village, the 2,000-plus-acre Fells has been under state protection since 1893. The cessation of logging in the 1800s has allowed the forest to grow up, with some parts approaching mature status.

Saddler’s Woods (Haddon Township, N.J.): This 26-acre forest fragment in suburban Philadelphia was initially preserved by Joshua Saddler, a fugitive slave from Maryland. He purchased the land in the early 1800s and never cut the trees.

Oakland Forest (Portsmouth, R.I.): Fifteen minutes from Newport’s mansions, this 20-acre stand of old-growth beech was once part of an equestrian facility owned by the Vanderbilts. Protected under the Aquidneck Land Trust, the forest is ecologically significant because its trees appear resistant to beech bark disease.


FURTHER READING

  • As an active research site, Hutcheson Memorial Forest is closed to the public six days a week, but you can take a tour with a Rutgers ecologist on Sundays year-round. Visit the link above for details.
  • Read about an audacious effort to conserve old-growth forest in New England.
  • Learn more about AMC’s own forest conservation work.

 

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Lindsey Konkel

Lindsey Konkel, a freelance journalist based in New Jersey, writes about science, health, and the environment.