Whereas the demolition of massive dams within the West will get extra consideration, many of those often-obsolete obstructions are additionally popping out of northeastern streams and rivers—and herring are returning in droves
Dams block the circulate of a river to carry water in a reservoir, which can be utilized for agriculture, recreation, family wants or business. The circulate of water via a dam can generate hydroelectric energy. Getting old dams are being dismantled throughout the nation, restoring the pure circulate to rivers.
Jukka Jantunen / Shutterstock
In 1859, a committee of farmers in Billerica, Massachusetts, having grown irked by a dam on the Harmony River, employed a surveyor to justify its destruction. The dam, which powered a textile manufacturing facility owned by an industrialist named Charles Talbot, was allegedly flooding their fields and spoiling their hay; now they needed the wall and its reservoir gone. They hoped the surveyor’s proof would persuade a court docket to order its obliteration. The surveyor—a conscientious, lushly bearded man of fine reputation—set about plumbing the Harmony’s backside, measuring its bridges and scrutinizing high-water marks. In reality, he didn’t love the work, describing surveying as “drudgery” in his journals. Henry David Thoreau’s truest ardour, in fact, wasn’t surveying land, however writing about it.
Except for the paycheck, the now-legendary creator had one other motivation to take the Harmony job: He despised the Talbot Mills Dam. A decade earlier, Thoreau had printed the travelogue A Week on the Harmony and Merrimack Rivers, by which he inveighed in opposition to the dam for blocking the passage of spawning fish, particularly American shad. “Poor shad! The place is thy redress?” Thoreau wrote. Though Thoreau’s surveys supported the farmers’ case, on attraction, the state of Massachusetts permitted the dam to stay. This could’t have stunned Thoreau, who knew that dams made for intractable opponents. “Perchance, after just a few hundreds of years, if the fishes shall be affected person, and cross their summers elsewhere in the meantime, nature may have leveled the Billerica dam,” he wrote.
The Talbot Mills Dam in Billerica, Massachusetts—proven on this 1908 {photograph}—has vexed environmentalists, agrarians and native fish for hundreds of years. Public area by way of Billerica Public Library
For a lot of fish-blocking dams, nonetheless, it hasn’t taken “just a few hundreds of years” to degree them in spite of everything. Since 1912, greater than 2,300 dams have been purged from waterways in the USA, most within the final quarter-century. The dam-removal motion hit its apogee in 2024, when, by the accounting of the nonprofit American Rivers, dam removals reconnected greater than 2,500 miles of once-fragmented waterways. The yr’s largest and best-publicized dam obliteration occurred on the Klamath River, the place the dismantling of 4 getting old hydroelectric dams opened greater than 400 miles of spawning habitat in California and Oregon to chinook salmon, which recolonized the watershed so quickly that conservationists described the comeback as “magical.” Earlier than the Klamath, the nation’s largest undamming befell on Washington State’s Elwha River, the place two fish-blocking partitions have been obliterated on behalf of chinook, coho, steelhead and different salmonids.
After this and different dams have been faraway from the Elwha River in Washington State, long-absent salmonids got here surging again. Trish Drury / Alamy Inventory Photograph
But it might be a mistake to presume that dam removals primarily profit western salmon rivers. Although they’re sometimes smaller in scale and obtain much less fanfare, the bulk happen in jap states. In 2024, the Blake Higgins Dam got here tumbling down in Vermont, the Edes Falls Dam departed the Crooked River in Maine, and the Kimball Brook Dam vanished from New Hampshire. Pennsylvania tore out 27 out of date limitations that yr, none taller than round 20 ft. Even the three-century-old Talbot Mills Dam that so vexed Thoreau could quickly be taken down.
“We’re on this dam-removal renaissance, the place we’re shedding limitations quicker than we’re placing them up for the primary time in historical past,” says Nathan Furey, a fish biologist on the College of New Hampshire. Per one stock, nonetheless, a minimum of 35,000 dams nonetheless truncate northeastern fish runs, together with greater than 3,000 in Massachusetts, 5,000 in Connecticut and 9,000 in New York.
By the numbers: Klamath River dam removing
The $500 million challenge to take away 4 dams alongside the Klamath River in California and Oregon befell over a few years, with the river flowing freely by August 2024. The work opened 400 miles of salmon habitat, and hundreds of the fish handed a former dam web site in each 2024 and 2025.
Among the many states destroying dams, albeit steadily, is New Hampshire, and one late-April morning I climbed right into a automotive with Furey to tour just a few of its newly free-flowing rivers. Furey had come to the Granite State in 2018 a neophyte to dam removing, having finished most of his graduate analysis on comparatively undeveloped Pacific salmon rivers in British Columbia. “However whenever you’re the fish man on the College of New Hampshire, folks need you to inform them what occurs when a dam comes out,” he stated as he navigated Durham’s leafy streets. “There’s lots of people trying to you for solutions.”
Furey’s area is the Nice Bay watershed, a tidal estuary fed by an arterial community of seven rivers. Traditionally, these waterways teemed with a roster of diadromous fishes: species that cut up their lives between freshwater and the ocean. That included Atlantic salmon, shad, sea lamprey, American eels, tomcod, sturgeon and, most quite a few of all, alewives and bluebacks, a pair of silvery, foot-long fish collectively generally known as river herring. Sharks, striped bass, cod, seals, seabirds and different predators devoured river herring as they approached the estuary every spring, and juvenile Atlantic salmon could even have timed their departure from river to ocean to coincide with alewives’ return. Whereas cormorants and otters gorged on alewives, younger salmon slipped downstream undetected. There’s security in numbers, and alewives provided such prodigious numbers earlier than they crashed that one historian deemed them “passenger pigeons of the ocean.”
Alewives suffered as settlers expanded their presence in North America. Schuchart / Shutterstock
Like their avian analogues, alewives fared dismally throughout North America’s colonization. Starting within the 1600s, jap colonists launched a dam-building spree, impounding and harnessing streams to spin waterwheels and energy mills—gristmills for grinding corn, sawmills for hewing logs, paper mills for pulping wooden, textile mills for spinning cloth. By the mid-1800s, greater than 65,000 mills stapled jap creeks, with catastrophic penalties. Over the previous 4 centuries, scientists have calculated that New England’s dams have disadvantaged its ecosystems of practically 20 billion kilos of alewives—roughly the load of 300,000 humpback whales.
To point out me what occurs when a type of fish-blocking partitions comes down, Furey took me to the Bellamy River, its frothing course beforehand straddled by a sprawling brick compound, former headquarters of Sawyer Woolen Mills. The textile mill, lengthy defunct, had been transformed to residences within the Eighties, however its two dams had lingered, funneling the Bellamy via a slender, fish-stopping pipe. As they aged, the dams additionally turned flood hazards, and in 2019 and 2020 a coalition of businesses, nonprofits and the condo advanced’s proprietor demolished them. Now the unfettered river churns beneath the brick colossus, ripping over a recontoured backside of bouldery swimming pools and pockets.
The dams are lengthy gone, however can the herring navigate the impediment course they left behind? “Alewives will not be salmon—they’ll’t soar,” Furey defined over the Bellamy’s roar. “They’re not massive, highly effective swimmers like sturgeon; they’re not eels that may climb and crawl.” After the dams got here out, the state tried to rely returning alewives with visible surveys—in different phrases, by staring on the stream and tallying fish, an clearly imprecise methodology. “We do not know what number of fish come again right here,” Furey stated.
Furey had been tasked with answering that query. He and his college students would seize alewives as they entered the Bellamy and implant them with trackers, together with rice-grain-size microchips generally known as PIT tags, or passive built-in transponders, to determine what share of returning herring managed to skitter via the rapids. We strolled previous the condo advanced and upstream to look at Furey’s lab members arrange the PIT tag reader that might register every fish. A steel field, containing batteries and a recorder, was chained to a tree close to the financial institution; from it, a cable ran to a riffle, able to log the serial variety of any tagged alewife that wriggled previous: a contemporary expertise to surveil an historical fish.
Nathan Furey, a fish biologist on the College of New Hampshire, makes an attempt to quantify what number of alewives and different fish are returning to New England rivers after dams come down. Ben Goldfarb
As Furey’s colleagues fiddled with the PIT tag array, they have been noticed with curiosity by the residents of the Sawyer Mills residences, lots of whom had taken their lunches outdoors to savor the balmy spring day. Whereas different wildlife migrations, just like the trans-hemispheric flights of Arctic terns, unfold largely past human ken, New England’s diadromous fish usually cross via neighborhoods and backyards. “They don’t want pristine environments—they are often proper right here,” Furey stated.
Many West Coast salmon runs collapsed throughout the span of human reminiscence, however New England’s rivers have been plugged for thus lengthy that few residents know that they as soon as ran silver with bluebacks, alewives and shad. “It’s a problem to speak to folks about these fish, as a result of they don’t have any cultural reminiscence,” Furey stated. Fish depletion, due to this fact, is usually a self-reinforcing cycle. The less fish there are, the much less the general public cares about them, a suggestions loop the biologists John Waldman and Karin Limburg dubbed eco-social anomie.
Dam removing is usually described as rewilding rivers, however it additionally liberates the human creativeness. In a 2014 paper, the ecologist Loren McClenachan and colleagues printed interviews with Mainers dwelling alongside rivers the place alewife runs had been restored, amongst them the Sebasticook, up which practically two million herring swam instantly after a dam got here out in 2008. McClenachan’s topics have been jubilant: The return of herring had instilled satisfaction, generated income from fishing and tourism, and solidified social bonds as children and lobstermen gathered to look at fish ascend. If eco-social anomie describes a societal forgetting, dam removing achieves the alternative—a “collective remembering,” as McClenachan put it, that cures our amnesia and unshifts our baselines.
A migrating herring Cami Johnson / Shutterstock
Whereas knocking out main dams on foremost stems achieves dramatic outcomes, loads of smaller obstacles require redress, too. In 2025, 12 years after the demolition of two dams, an astonishing six million river herring returned to Maine’s Penobscot River—double the determine from simply two years prior. However though the river’s decrease foremost stem runs free for 40 miles, its capillary networks of tributaries stay “considerably missed,” in keeping with Joshua Royte, senior conservation scientist on the Nature Conservancy. Whereas the Penobscot Nation and others have eliminated many limitations, dozens of mill dams and undersized culverts nonetheless choke the watershed’s dendritic headwaters, thwarting migratory fish from accessing a number of the basin’s most ecologically essential areas—spawning grounds for sea lamprey and salmon, chilly local weather refugia for brook trout, grottos overhung with leaves that feed aquatic invertebrates.
“In the event you shield and join large networks of those headwaters, you may preserve productiveness all the best way downstream,” Royte says. “A chilly-water tributary only a quarter-mile lengthy could possibly be actually essential.”
Contemplate Sedgeunkedunk Stream, a Penobscot tributary the place dam removing reopened round 2.8 miles of creek and boosted populations of native sea lamprey. Sea lamprey, like Pacific salmon, accumulate nitrogen and phosphorous throughout their time at sea, then die after migrating into rivers to breed. Their carcasses feed animals similar to snapping turtles and raccoons, and the marine-derived vitamins of their flesh fertilize algae and forests. Ecologist Steve Coghlan, who studied lamprey’s restoration in Sedgeunkedunk, as soon as described to me watching the eel-shaped fish spawn, seizing rock after rock with their mouths and positioning them with utmost care of their redds, or nests. Behind the amorous lamprey hovered shoals of shiners, dace and fallfish, ready as if on a buffet line for eggs and the drifting aquatic bugs the lamprey dislodged—a fragile symbiosis that rose when a wall fell.
Regardless of the virtues of free-flowing rivers, nonetheless, many New Englanders stay as hooked up to their dams as they have been throughout Thoreau’s day. After stopping on the Bellamy, Furey took me to the Oyster River, the place a century-old wall known as Mill Pond Dam unfold and slowed the river’s circulate—only one in a sequence of dams that had stoppered the river because the 1600s. Water sheeted gracefully over the dam’s lip and frothed at its base, a scene I needed to admit was picturesque. We inspected the fishway, a sloping ramp by way of which river herring and different species surmounted the dam—although, Furey identified, giant fish similar to sturgeon seemingly couldn’t navigate the ladder’s tight corners and even match into its slender channel. Nor did the fishway stop the pond from changing into a heat, low-oxygen puddle in summer season, or cease herons and different predators from selecting off out-migrating juvenile herring as they struggled via the pond’s slack water.
The dam hadn’t served any industrial function in a long time. However not everybody needed to tear it down. On a garden throughout the Oyster’s mirrored floor, an all-caps signal insisted that we “HELP SAVE MILL POND DAM.” Dozens of removals have been thwarted or delayed by native dam fans, who’re generally described as NOOMBYs—Not Out of My Yard. Many NOOMBYs take into account native dams indispensable ties to their group’s previous; in Billerica, some city officers have objected to the demolition of the Talbot Mills Dam on the grounds that “it has lengthy served as a logo of the Industrial Revolution” that is still “unquestionably one of many main focal factors within the space.” Dams and reservoirs additionally accrue leisure worth: They’re the scenic, still-water backdrops in opposition to which individuals paddle kayaks, feed geese and educate their youngsters to catch sunfish.
Some residents and historical past buffs argued to maintain and restore the faltering Mill Pond Dam on New Hampshire’s Oyster River, however the ecological and monetary logic for destroying the dam received out in the long run. Ben Goldfarb
Today, the sentimental attachment to defunct dams seems to be waning—and Mill Pond Dam is Exhibit A. In 2002, the state of New Hampshire declared the dam structurally poor and ordered the town of Durham to restore it, a course of that engineers estimated would value way over merely tearing it down. After residents protested the potential of removing, the town quickly dropped the thought. However the ecological and monetary logic was too overwhelming to disregard, and, in 2022, the problem was put earlier than a poll initiative, by which Durham voters elected to destroy the dam by practically a three-to-one margin. The $3.1 million demolition challenge started this summer season and can conclude in 2027 with the planting of native vegetation across the now-drained reservoir.
“Traditionally, the Oyster [River] would’ve boiled with river herring,” Furey stated as we gazed on the doomed dam. “That’s the historical past I’m fascinated about.”
But historical past is just one issue preserving previous dams—present occasions play a job, too. Though many northeastern dams are out of date granite-block affairs, a whole lot are of Twentieth-century classic and nonetheless feed hydroelectricity to regional grids. Some are owned by cities, some by utilities; nonetheless others are the property of firms, personal landowners or buyers who purchase them inside renewable power portfolios. Although they’re hardly main suppliers of power—some solely energy a handful of properties—it may be tough to justify taking any electrons offline in a world of spiking power costs and explosive data-center development. Nonetheless, as small-scale hydroelectric dams age, the price of repairing them, and the flood threat they pose within the occasion of failure, could make them financial liabilities that their house owners are keen to dump—usually as important a motivator for dam removing as fish passage.
In the meantime, the Trump administration is hampering dam removing efforts in a number of methods. The Nationwide Oceanic and Atmospheric Administration, which has spearheaded dozens of dam removals round New England, faces dramatic cuts to its employees and finances. The Culvert Aquatic Organism Passage Program, a bipartisan infrastructure initiative that earmarked $1 billion to take away highway culverts and different fish limitations, has at instances seen delays within the evaluation and funding of functions. And widespread cancellations of photo voltaic and wind power initiatives have disadvantaged grids of energy sources that would substitute hydroelectric dams.
“The shortage of perception that authorities could be an essential companion, the reductions in funding, the assault on the staffing of companion businesses—it’s not making this work any simpler in any respect,” says Andrew Fisk, northeast regional director for American Rivers.
Plymouth, Massachusetts, has lengthy been an enthusiastic purger of dams, and one weekend I visited throughout its Herring Run Competition, a celebration of the resurgent alewife inhabitants that yearly runs up City Brook, the stream at Plymouth’s coronary heart. The day was cool and damp, and I adopted a posse of dads in Purple Sox sweatshirts and youngsters in rainboots up the trail that paralleled the creek. Somebody had chalked “LOOK FISH” on the asphalt, and I glanced streamward to search out alewives holding in small pods, weaving round one another of their easy means.
The upper I walked, the thicker the fish acquired, till I reached the bottom of the Plimoth Grist Mill, the final dam left in City Brook, the place they queued as much as enter a ladder in an aggregation as thick and black as tar. A man holding a Dunkin’ cup eyed a belly-up alewife and quipped, “He ain’t doing so scorching.”
Above the dam, which was preserved for cultural training and fitted with fish and eel ladders, the herring pageant was in full swing: an acoustic guitarist jamming, children grinding corn on the vintage mill, enviros tabling for fish-adjacent causes. “My household appears to be like ahead to the herring run yearly,” Malissa Costa, a Mashpee Wampanoag cultural chief, advised me after I stopped at her tribe’s kiosk. “We take into account these fish our ancestors, linked beings to us.” Although Massachusetts has prohibited alewife harvest since 2006, the Wampanoag are exempt, and Costa takes round 20 every spring with nets and generally her naked palms.
Humorous sufficient, Costa doesn’t very like the style of the fish: “You ever smelled herring?” she stated, wrinkling her nostril. “It’s just like the fishiest fish.” As an alternative, she items her catch to elders and tribal members in want. “Yearly I really feel an obligation to go on the market and get the herring.”
As they emerged from the gristmill’s ladder, alewives slid via a digital camera field to be counted by volunteers monitoring the feed from dwelling—a literal dwell stream. For hundreds of years, these fish would have confronted 5 further dams alongside a span of simply 1.5 miles, which powered the manufacturing of grain, textiles, leather-based sneakers, anchors and extra, en path to their headwater spawning pond. Now their journey is free and clear, and I couldn’t blame the gawkers applauding every fish that emerged from the ladder. “It’s laborious not to root them on in spite of everything we’ve finished to them,” agreed David Gould, director of the city’s setting division, as we fish-watched.
Gould is the individual most chargeable for City Brook’s transformation, and I urged we stroll upstream to see what he’d completed. “This was once underwater,” Gould stated each couple of minutes as we adopted the creek up a path, gesturing at some area or park or woodlot as soon as submerged by a reservoir. Often we noticed vestiges of former impoundments: a dock’s rotting skeleton, a high-water stain on a glacial erratic. The masonry of a few previous dams, which had doubled as city streets, had been artfully transformed into bridges; the ruins of others light into the greenery.
In Plymouth, Massachusetts, a former dam has been transformed to a bridge that lets fish cross unimpeded beneath it. Ben Goldfarb
Although City Brook’s dams had been outfitted with fish ladders, the passages have been shoddy, overlong and laborious for fish to search out amid turbulent swimming pools. “You’d see hundreds of fish washing again down, simply bruised and battered and lower up,” Gould stated. Among the many most egregious offenders was the Billington Road Dam, and within the early 2000s the city of Plymouth sought federal help to restore its defective ladder. The request reached Eric Hutchins, a now-retired restoration biologist at NOAA, who proposed eradicating the dam altogether as a substitute of fixing it. In 2002 the destruction, overseen by Gould, was carried out by an Military Reserve engineering battalion.
Energized, Gould started to select off the brook’s different dams—Water Road, Plymco, Holmes—with numerous pots of funding. In a city with a historical past as layered as Plymouth’s, he found, a lot of dam removing turned out not to be dam removing. Asbestos shingles needed to be peeled off mill buildings; rights of means needed to be extinguished; contaminated sediment needed to be landfilled. The stream itself needed to be rebuilt, boulders and bends and riparian crops restored to destitute reservoir bottoms. And the permits—so many permits. “You’re utilizing the identical regulatory framework that allows, like, a Walmart,” Gould stated.
By the point I visited Plymouth, Gould had attained virtually mythic standing amongst river restorationists. “Dave has in all probability eliminated extra dams single-handedly than anyone east of the Mississippi, and perhaps west,” Hutchins tells me. Gould didn’t appear fully comfy with being a dwelling legend. He’d lately spoken at a fish-passage convention alongside delegates from the Klamath and different large western watersheds. “All these persons are speaking about opening up 50 miles of habitat for these large salmon, and I’m speaking about these initiatives the place we opened up, like, a 3rd of a mile at a time for these little herring,” he recalled sheepishly. But few dam removals may rival City Brook for sheer manufacturing. Earlier than Gould started ripping out dams, round 25,000 herring returned to the brook yearly. Now, many runs exceed 200,000.
Replicating such success on a nationwide scale would require a raft of reforms: vastly extra funding, smoother allowing processes, extra photo voltaic power to exchange hydropower. To realize American Rivers’ purpose of eradicating 30,000 dams by mid-century, the tempo of dam removing must speed up by roughly an order of magnitude. But all these coverage modifications have to be preceded by social transformation—by people, hundreds of thousands of them, witnessing free-flowing streams once more operating chock stuffed with fish. As American Rivers’ Fisk places it: “Proximity to abundance is transformational.”
Forty minutes of strolling introduced me and Gould to the freshwater pond the place the alewives swarming in City Brook would quickly spawn. Typically, Gould pushes out a kayak to look at breeding fish swirl among the many lakeshore willows, his personal personal celebration of a herring run that had fed pilgrims and sustained the Wampanoag because the finish of the final ice age. “To me, the single-most historic factor in Plymouth is that this brook,” he stated. Moderately than being a power performing in opposition to historical past, fish have been historical past—and in contrast to mill dams, they’d a future.
A model of this text was initially printed by bioGraphic, an unbiased, nonprofit journal that publishes journalism about biodiversity loss and conservation.