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How beavers are reshaping Adirondack forests

On April 27, 1905,
a four-man “Army of Liberation” departed from Old Forge for the Fourth Lake of the Fulton Chain, two zinc-lined crates stowed aboard their rowboats. After a day of rowing, the men ditched their vessels and hiked 12 miles down a snowbound trail—“over hills, through swamps, and across rivers,” wrote Harry  Radford, the quartet’s leader. The party lugged the ungainly boxes in shifts, switching handlers every 10 minutes to ease the burden, and spent the night at a cabin owned by a hermit named Frank Gray. The next morning, the group toted their crates to a nearby stream to release their cargo: a pair of beavers. A year later, Gray spotted a lodge of mud and sticks in the same spot. The beavers had settled down.

Four centuries ago, a beaver colony in the Adirondacks wouldn’t have warranted a second thought. Once, wrote Radford, “every river, brook, and rill… [was] thickly peopled with these industrious and prolific animals.” But the fur trade—so influential that Albany was once known as Beverwyck—spelled doom for the aquatic hordes. By the 1670s, 80,000 pelts were flowing down the Hudson River annually, bound for Europe for felting into fashionable hats. When the state finally banned trapping in 1895, fewer than 10 beavers remained in New York.

The beaver’s story, however, wasn’t over yet. In 1904, the state devoted $500 to beaver reintroduction and bought seven live animals from Canada’s display at the Louisiana Purchase centennial in St. Louis. The acquisition, like the Louisiana Purchase itself, proved a spectacular bargain: the imports, along with other relocatees, flourished and bred. Scarcely a decade later, the Adirondacks hosted a stunning 15,000 beavers. These days up to 70,000 paddle-tailed builders swim the region, nearly as many as greeted Samuel de Champlain. And we’re just beginning to figure out how profoundly their return has restructured our forests.

The North Woods, scientists wrote in 2013, are defined by paradox—“at once largely unchanged and completely transformed” from their precolonial state. Nearly all the tree species that dominated the Northeast 400 years ago—sugar maple, American beech, yellow birch—remain abundant.

Despite appearances, however, the North Woods have changed dramatically. Timber harvest came late to the Adirondacks, but by the early 1800s loggers were feeding charcoal from hardwoods into the blast furnaces of the MacIntyre Iron Works and driving pine logs down the Hudson River. After legal protections in 1885, the region’s forests began to creep back, a blanket of second-growth hardwoods smothering hills and valleys. What our woods have regained in density, they lack in heterogeneity. Many stands are roughly the same age, height and species makeup, missing the multitiered levels and open patches favored by many creatures.

“We’re trending toward these mature forests without a lot of structural and compositional diversity,” says John Stella, an associate professor at the SUNY College of Environmental Science and Forestry (SUNY-ESF). Wildfires are suppressed, windstorms rare, logging nearly nonexistent. Disrupting the monotony of New York’s woods thus falls to a tree-felling, dam-building, pond-creating engineer: Castor canadensis, the North American beaver.

Beavers, as any streamside homeowner can attest, are unparalleled agents of disturbance. Their disorderly conduct may not appeal when they’re flooding your yard or mowing down your orchard, but it’s a profound boon to ecosystems. By broadening free-flowing streams, turning single-thread creeks into braided ones, and permitting sunlight to reach the forest floor, they create gaps within otherwise homogeneous woods. The transformation continues long after beavers depart, as ponds fill with sediment and emergent plants and solidify into lush meadows. These patchy, protean landscapes are chockablock with life-supporting niches. In 2002, researchers found that beaver-modified habitats in the Adirondacks increased plant diversity by 33 percent. Seven years later, scientists discovered the region’s beaver wetlands produced 23 times more young wood frogs than did seasonal pools.

“Whenever I’m hiking somewhere and see a beaver pond, I always think, OK, what cool species am I going to see today?” says Paul Jensen, senior wildlife biologist at the Department of Environmental Conservation (DEC). “The possibilities are endless.”

While most research has focused on beavers’ aquatic engineering, their logging skills are equally important. For 10 years, John Stella and a procession of graduate students have studied beavers’ tree-cutting habits at SUNY-ESF’s Huntington Wildlife Forest, a 15,000-acre research site in Newcomb. Scientists at the Adirondack Ecological Center have monitored Huntington’s colonies—the basic beaver family unit, consisting of the breeding parents and two to six offspring—for over three decades, generating one of the country’s most comprehensive data sets. As a result, there are few better places to study the long-term activities of beavers than the central Adirondacks.

Beavers are “choosy generalists”—although they’ll eat just about anything in a pinch, they prefer the inner bark of easily digestible poplars and willows. Size matters in tree selection, too: after all, beavers not only debark their woody victims, they use the peeled sticks to build their dams and lodges. In 2011, Anna Harrison, a SUNY-ESF master’s student, found that Huntington’s beavers favor striped maple and American beech—the latter of which readily regrows, Hydra-like, after being cut down. By repeatedly coppicing beech, Harrison discovered, the rodent silviculturists created a “positive feedback” of regenerating sprouts, effectively cultivating their own food source and construction supplies—and clearing space for red maple and red spruce seedlings. Beavers, in other words, keep forests young.

As the woods change, so do their inhabitants. For six weeks in 2013, another student, Carissa Alza, and other observers arose before sunrise to identify birds by sight and sound. The results were telling: On average, beaver areas supported 10 more bird species than did forest interiors, and 12 more than undammed streams. And it wasn’t just water-loving wood ducks and kingfishers that preferred beaver flowages—forest-edge specialists like the least flycatcher and white-throated sparrow also seemed to appreciate the open canopy. For shrub nesters like the chestnut-sided warbler, meanwhile, the dense, shrubby understory formed by all those coppicing beeches offered invaluable protection.

“It seems like a pretty coherent story,” John Stella says. “Beavers create more young forest patches, and wildlife responds favorably to that. These beaver areas are one of the few sources of natural disturbance we have left.”

From a conservation standpoint, allowing beavers to recolonize every Adirondack stream might seem like a no-brainer. But it’s not that easy. During beavers’ long absence, we slapped down roads, railroads and towns in the same floodplains they once inhabited. While you can’t blame beavers for reclaiming their old haunts, there’s no denying they’re troublemakers. In 1993, the DEC estimated beavers inflicted $5.5 million in property damage statewide, and Paul Jensen says his department responds to around 350 beaver-related complaints annually, from clogged culverts to gnawed timber.

In the lightly peopled Adirondacks, conflicts aren’t as epidemic as elsewhere in the Northeast. Still, beaver management is a delicate balancing act. Reaping beaver benefits while mitigating problems has become the focus of John Stella’s lab at SUNY-ESF. Yet another master’s student, Rachel Zevin, is developing a computer model that will identify which areas are best suited for beavers, and which might produce clashes with humans—information that should help biologists figure out where to encourage beavers’ return. The project is based on the Beaver Restoration Assessment Tool, or BRAT, a model that scientists are using to guide rodent restoration elsewhere.

“Anything beaver-related gets some interest these days,” says Joe Wheaton, a geomorphologist at Utah State University and BRAT’s inventor. “There are a lot of places where we can eke out some habitat gains by allowing a rodent to do what it does—and do it for free.”

How beavers will shape New York’s forests in the future, however, is an open question. According to Stacy McNulty, associate director of the Adirondack Ecological Center, Huntington’s beavers have begun to mysteriously decline, from around 30 colonies to 20. Perhaps the creatures depleted their food supply, McNulty says, or maybe coyotes realized that juvenile beavers make tasty morsels. Another potential culprit: climate change. The Adirondacks’ formerly stable precipitation patterns have lately gone haywire, fluctuating between storms that blow out beaver dams and droughts that dry out ponds. “It might be getting harder for beavers to manage the landscape in the way they need,” McNulty says. For all the services that beavers provide, there’s only so much they can do in a warming world.

On the first day of 2018—a morning that dawned 20 below—I snowshoed to a beaver complex near Johnsburg, determined to begin my year in the company of the Adirondacks’ second-most-influential mam—-mal. The pond, tucked into the floodplain of a roadside creek, was veneered in ice, the lodge a snowbound island, snug against black bears and the elements. I tried to approach, heard cracks and creaks, and backed off. But the beavers were home, I knew, their presence betrayed by the brushy willow cache entombed in ice, the larder that would sustain them through the brutal winter. I imagined them there, secure in the aqueous dark of their frozen-hard lodge: enduring, hardy, patient, awaiting spring and the resumption of their work.

Ben Goldfarb is the author of Eager: The Surprising, Secret Life of Beavers and Why They Matter (2018, Chelsea Green Publishing).

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