Removing Dams Could Save Atlantic Salmon From Extinction
By Tara Lohan
Atlantic salmon have a challenging life history — and those that hail from U.S. waters have seen things get increasingly difficult in the past 300 years.
Dubbed the "king of fish," Atlantic salmon once numbered in the hundreds of thousands in the United States and ranged up and down most of New England's coastal rivers and ocean waters. But dams, pollution and overfishing have extirpated them from all the region's rivers except in Maine. Today only around 1,000 wild salmon, known as the Gulf of Maine distinct population segment, return each year from their swim to Greenland. Fewer will find adequate spawning habitat in their natal rivers to reproduce.
That's left Atlantic salmon in the United States critically endangered. Hatchery and stocking programs have kept them from disappearing entirely, but experts say recovering healthy, wild populations will require much more, including eliminating some of the obstacles (literally) standing in their way.
Conservation organizations, fishing groups and even some state scientists are now calling for the removal of up to four dams along a 30-mile stretch of the Kennebec River, where about a third of Maine's best salmon habitat remains.
The dams' owner — multinational Brookfield Renewable Partners — has instead proposed building fishways to aid salmon and other migratory fish getting around dams as they travel both up and down the river. But most experts think that plan has little chance of success.
A confusing array of state and federal processes are underway to try and sort things out. None is likely to be quick, cheap or easy. And there's a lot at stake.
"Ultimately the fate of the species in the United States really depends upon what happens at a handful of key dams," says John Burrows, executive director of U.S. programs at the Atlantic Salmon Federation. "If those four projects don't work — or even if just one of them doesn't work — you could basically preclude recovering Atlantic salmon in the United States."
The best place for salmon recovery is in Maine's two largest watersheds.
"The Penobscot River and the Kennebec River have orders of magnitude more habitat, production potential and climate resilient habitat" than other parts of the state, says Burrows.
The rivers and their tributaries run far inland and reach more undeveloped areas with higher elevations. That helps provide salmon with the cold, clean water they need for spawning and rearing. Smaller numbers of salmon are hanging on in lower-elevation rivers along the coastal plain in Maine's Down East region, but climate change could make that habitat unsuitable.
"There's definitely concern about how resilient those watersheds are going to be for salmon in the future," says Burrows. "To recover the population, we need to be able to get salmon to the major tributaries farther upriver, in places where we're still going to have cold water even under predictions with climate change."
One of those key places is the Penobscot, which has already seen a $60 million effort to help recover salmon and other native sea-run fish. A 16-year project resulted in the removal of two dams, the construction of a stream-like bypass channel at a third dam, and new fish lift at a fourth. In all, the project made 2,000 miles of river habitat accessible.
Veazie dam on the Penobscot River is breached in 2013 as part of a river restoration project. Meagan Racey / USFWS
While there's still more work to be done on the Penobscot, says Burrows, attention has shifted to the Kennebec. The river has what's regarded as the largest and best salmon habitat in the state, especially in its tributary, the Sandy River, where hatchery eggs are being planted to help boost salmon numbers.
"That's helped us go from zero salmon in the upper tributaries of Kennebec to getting 50 or 60 adults back, which is still an abysmally small number compared to historical counts," says Burrows. "But these are the last of the wildest fish that we have."
The Sandy may be good salmon habitat, but it's also hard to reach. Brookfield's four dams stand in the way of fish trying to get upriver.
At the lowest dam on the river, Lockwood Dam in Waterville, there's a fish lift — a kind of elevator that should allow fish that enter it to pass up and around the dam. But if fish do find the lift — and only around half of salmon do — they don't get far.
"It's a terminal lift," says Sean Ledwin, division director of Maine's Department of Marine Resources' Sea Run Fisheries and Habitat. "The lift was never completed. So we pick up those fish in a truck and drive them up to the Sandy River."
That taxi cab arrangement isn't a long-term solution, though, and was part of an interim species protection plan.
Only the second dam, Hydro Kennebec, has a modern fish passage system. But how well that actually works hasn't been tested yet since fish can't get by Lockwood Dam. As part of a consultation process related to the Endangered Species Act, Brookfield has submitted a plan proposing to fix the fishway at Lockwood and add passage to the third and fourth dams.
But federal regulators found it inadequate.
"Brookfield's proposal was rejected by the Federal Energy Regulatory Committee [which oversees hydroelectric projects] and all the [federal management] agencies," says Ledwin. The company now has until May 2022 to come up with a new plan.
State scientists aren't convinced Brookfield's plan would work either.
"We have really low confidence that having four fishways would ever result in meaningful runs of all the sea-run fish and certainly not recovery of Atlantic salmon," says Ledwin. "We don't think that it's going to be conducive to recovery."
In addition to considerations related to the Endangered Species Act, Shawmut Dam, the third on the Kennebec, is currently up for relicensing, which triggers a federal review process by FERC.
And at the same time the Maine Department of Marine Resources has drafted a new plan for managing the Kennebec River that recommends removing Shawmut Dam and Lockwood Dam. A public comment period on the proposed plan closed in March.
Brookfield isn't happy with it and responded with a lawsuit against the state.
It was good news to conservation groups, however, which would like to see all four of the dams removed if possible — or at least a few of them.
"There's no self-sustaining population of Atlantic salmon anywhere in the world that we know of that have to go by more than one hydro dam," says Burrows. He believes that having Brookfield spend tens of millions of dollars on new fishways will just result in failure for salmon.
Atlantic salmon parr emerging from a stream bed in Maine. E. Peter Steenstra / USFWS
It's partly a game of numbers. Not all fish will find or use a fishway. And if you start with a low number of returning fish and expect them to pass through four gauntlets, you won't be left with many at the end.
"If you're passing 50% of salmon that show up at the first dam, and then you've got three more dams passing 50%, that means you're left with only an eighth of the population you started with by the end," says Nick Bennett, a staff scientist at the Natural Resources Council of Maine. "You can't start a restoration program where you're losing seven-eighths of the adults before they even get to their spawning habitat."
And getting upriver is just part of the salmon's journey. Juvenile salmon face threats going downstream to the ocean as well, including predation and warm water in impoundments. They also risk being injured or killed going through spillways or turbines. Only about half are likely to survive the four hydro projects.
Atlantic salmon, unlike their Pacific cousins, don't always die after spawning, either. So some adults will also make the downstream trek, too.
"Just looking at our reality, at least two dams need to go, hopefully three, and it would be amazing if all four would go," says Burrows.
The fate of Atlantic salmon hangs in the balance, but so do the futures of other fishes.
The Pacific coast of the United States is home to five species of salmon. And while the Atlantic side has just the one, it has a dozen other native sea-run species that have also seen their habitat shrink.
"Those dams are preventing other native species like American shad, alewives, blueback herring and American eel from accessing large amounts of historic habitat," says Burrows.
Ledwin says removing dams on the Kennebec could result in populations of more than a million shad, millions of blueback herring, millions of eels and hundreds of thousands of sea lampreys.
"The recovery of those species would actually help Atlantic salmon as well because they provide prey buffers and there are a lot of co-evolved benefits," he says.
Salmon are much more successful at nesting when they can lay their eggs in old sea lamprey nests, explains Bennett. "But sea lamprey are not good at using fish lifts and we've essentially blocked 90% of the historic sea lamprey habitat at Lockwood dam. We need to get those fish upstream, too."
Dam removal advocates don't have to look too far to find an example of how well river ecosystems respond when dams are removed.
The removal of the Edwards Dam on the lower Kennebec River in 1999 and the Fort Halifax Dam just upstream on the Sebasticook in 2008 helped ignite a nationwide dam-removal movement. It also brought back American shad, eel, two native species of sturgeon and millions of river herring to lower parts of the watershed.
Alewives returned by the millions after the Edwards and Ft. Halifax dams were removed. John Burrows / ASF
"We've got the biggest river herring run in North America now due to the dam removals," says Ledwin. "And the largest abundance of eel we've ever seen on the lower Kennebec."
The resurgence of native fishes helps the whole ecosystem. When they returned, so too did eagles, osprey and other wildlife.
"When people see all those fish in the river and the eagles overhead, it just kind of blows their minds because they never realized what had been lost for so long in our rivers," says Burrows.
Rebuilding key forage fish like herring also benefits species that live not just in the river, but the Gulf of Maine and even the Atlantic Ocean. The tiny fish feed whales, porpoises and seabirds. They're also used for lobster bait and can help rebuild fisheries for cod and haddock, which has economic benefits for the region, too.
"We have to rebalance the scales if we want to have marine industries and commercial fishing industries and if we want the ecological benefits of what sea-run fisheries do for us," says Bennett.
The Path Ahead
The process to determine whether any — or all — of the four Kennebec dams that stretch from Waterville and Skowhegan are removed will take years, a diverse coalition, financial resources and agreements to meet the concerns of communities and the dam owner.
"These things come down to compromise, so there may be situations where one of those dams might not be a candidate for economic or social reasons," says Burrows. "But it will be interesting to see if in the next couple of years we can get to a place where we can have meaningful conversations with federal agencies, the dam owner and continue to engage the communities about the potential of removal at some of these sites."
And if removal of the four dams did happen, it wouldn't open up the river all the way to its headwaters. Another nine dams still lie upstream in the watershed that obstruct fish passage.
"Some of those are major dams in terms of power, production and economics," says Burrows. "So we're not calling for those to be removed."
The four lower dams provide just 46 megawatts of power — enough to supply about 37,000 homes and 0.43% of the state's annual electricity generation. It's a small amount of power relative to the damage they cause sea-run fish, says Bennett.
"By comparison we expect to add 1,200 megawatts of solar generation in the next five years," he says. "So these four dams aren't particularly important in our climate fight." And removing them would open up substantial amounts of habitat to aid salmon recovery that seem worth the tradeoff in lost power.
That's not the case, he says, for the nine larger dams upstream.
"We need those dams. We need hydroelectric power in Maine," says Bennett. "But we made big mistakes in our past use of our rivers. And we went way overboard in favor of hydroelectric power at the expense of fish."
Outside of the rivers, Atlantic salmon still face a tough road. Climate change is warming ocean temperatures, changing salinity and altering food webs. But having so many unknowns in the marine environment in the coming decades provides more reason to focus efforts on restoring rivers where scientists already know what works, says Burrows.
And if that's done right, the benefits will extend far beyond salmon.
"It's not just about salmon — it's about these other native fish, it's about the wildlife, water quality, economic opportunity for ground fishermen and lobstermen, and more sustainable forms of recreation and community development," says Burrows. "If we remove a dam or two here and rebuild these fish populations to pretty big levels that really impacts a whole bunch of different parts of society. That's what we want to try to do here on the Kennebec."
Reposted with permission from The Revelator.
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NOAA OKEANOS Explorer Program, 2013 Northeast U.S. Canyons Expedition
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The tropical water at the equator is renowned for having the richest diversity of marine life on Earth, with vibrant coral reefs and large aggregations of tunas, sea turtles, manta rays and whale sharks. The number of marine species naturally tapers off as you head towards the poles.
The Bell Curve is Warping Dangerously<img class="rm-lazyloadable-image rm-shortcode" lazy-loadable="true" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNjAzODUwNi9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY3NzE1OTU4N30.qQL3P1IvA7Cwj_UbsrAL6MVZvafXGZc7hlAFieLPvso/img.png?width=980" id="9bbfd" width="1580" height="872" data-rm-shortcode-id="16ca57badee20ad55037706875f813f4" data-rm-shortcode-name="rebelmouse-image" />
If you look at each line in this chart, you can see a slight dip in total species richness between 1955 and 1974. This deepens substantially in the following decades. Anthony Richardson, Author provided<p>This global pattern — where the number of species starts lower at the poles and peaks at the equator — results in a bell-shaped gradient of species richness. We looked at distribution records for nearly 50,000 marine species collected since 1955 and found a growing dip over time in this bell shape.</p>
This Has Happened Before<p>We shouldn't be surprised global biodiversity has responded so rapidly to global warming. This has happened before, and with dramatic consequences.</p><p><strong>252 million years ago…</strong></p><p>At the end of the Permian geological period about 252 million years ago, global temperatures warmed by 10℃ over 30,000-60,000 years as a result of greenhouse gas emissions from volcano eruptions in Siberia.</p><p><a href="https://www.pnas.org/content/117/30/17578" target="_blank" rel="noopener noreferrer">A 2020 study</a> of the fossils from that time shows the pronounced peak in biodiversity at the equator flattened and spread. During this mammoth rearranging of global biodiversity, 90% of all marine species were killed.</p><p><strong>125,000 years ago…</strong></p><p><a href="https://www.pnas.org/content/109/52/21378" target="_blank" rel="noopener noreferrer">A 2012 study showed</a> that more recently, during the rapid warming around 125,000 years ago, there was a similar swift movement of reef corals away from the tropics, as documented in the fossil record. The result was a pattern similar to the one we describe, although there was no associated mass extinction.</p><p>Authors of the study suggested their results might foreshadow the effects of our current global warming, ominously warning there could be mass extinctions in the near future as species move into the subtropics, where they might struggle to compete and adapt.</p><p><strong>Today…</strong></p><p><a href="https://www.pnas.org/content/117/23/12891" target="_blank" rel="noopener noreferrer">During the last ice age</a>, which ended around 15,000 years ago, the richness of forams (a type of hard-shelled, single-celled plankton) peaked at the equator and has been dropping there ever since. This is significant as plankton is a keystone species in the foodweb.</p><p>Our study shows that decline has accelerated in recent decades due to human-driven climate change.</p>
The Profound Implications<p>Losing species in tropical ecosystems means ecological resilience to environmental changes is reduced, potentially compromising ecosystem persistence.</p><p>In subtropical ecosystems, species richness is increasing. This means there'll be species invaders, novel predator-prey interactions, and new competitive relationships. For example, <a href="https://www.abc.net.au/news/2019-09-13/sydney-growing-own-coral-reef-with-help-from-tropical-fish/11466192" target="_blank">tropical fish</a> moving into Sydney Harbour compete with temperate species for food and habitat.</p><p>This could result in ecosystem collapse — as was seen at the boundary between the Permian and Triassic periods — in which species go extinct and ecosystem services (such as food supplies) are permanently altered.</p><p>The changes we describe will also have profound implications for human livelihoods. For example, many tropical island nations depend on the revenue from tuna fishing fleets through the selling of licenses in their territorial waters. Highly mobile tuna species are likely to move rapidly toward the subtropics, potentially beyond sovereign waters of island nations.</p><p><span></span>Similarly, many reef species important for artisanal fishers — and highly mobile megafauna such as whale sharks, manta rays and sea turtles that support tourism — are also likely to move toward the subtropics.</p><p>The movement of commercial and artisanal fish and marine megafauna could compromise the ability of tropical nations to meet the <a href="https://sdgs.un.org/goals" target="_blank">Sustainable Development Goals</a> concerning zero hunger and marine life.</p>
Is There Anything We Can Do?<p>One pathway is laid out in the Paris Climate Accords and involves aggressively reducing our emissions. Other opportunities are also emerging that could help safeguard biodiversity and hopefully minimise the worst impacts of it shifting away from the equator.</p><p>Currently 2.7% of the ocean is conserved in <a href="https://mpatlas.org/" target="_blank">fully or highly protected reserves</a>. This is well short of the 10% target by 2020 under the UN Convention on Biological Diversity.</p><p>But <a href="https://www.gov.uk/government/topical-events/global-ocean-alliance-30by30-initiative/about#global-ocean-alliance-members" target="_blank">a group of 41 nations</a> is pushing to set a new target of protecting 30% of the ocean by 2030.</p><p>This "30 by 30" target could ban seafloor mining and remove fishing in reserves that can destroy habitats and release as much carbon dioxide as <a href="https://www.nature.com/articles/s41586-021-03371-z" target="_blank">global aviation</a>. These measures would remove pressures on biodiversity and promote ecological resilience.</p><p>Designing climate-smart reserves could further protect biodiversity from future changes. For example, reserves for marine life could be placed in refugia where the climate will be stable over the foreseeable future.</p><p>We now have evidence that climate change is impacting the best-known and strongest global pattern in ecology. We should not delay actions to try to mitigate this.</p><p><em><a href="https://theconversation.com/profiles/anthony-richardson-100303" target="_blank">Anthony Richardson</a>: Professor, The University of Queensland. <a href="https://theconversation.com/profiles/chhaya-chaudhary-1223419" target="_blank" rel="noopener noreferrer">Chhaya Chaudhary</a>: University of Auckland, <a href="https://theconversation.com/profiles/david-schoeman-111544" target="_blank" rel="noopener noreferrer">David Schoeman</a>: Professor of Global-Change Ecology, University of the Sunshine Coast, <a href="https://theconversation.com/profiles/mark-john-costello-1223418" target="_blank" rel="noopener noreferrer">Mark John Costello</a>: Professor, University of Auckland</em></p><p><em>Disclosure statement: Anthony Richardson receives funding from the Australian Research Council.</em></p><p><em>Chhaya Chaudhary works for Goethe University, Frankfurt am Main, Germany. During her PhD studies (2014- 2019), she received part- funding from the European Marine Observation Data Network (EMODnet) Biology project funded by the European Commission's Directorate—General for Maritime Affairs and Fisheries (DG MARE), and received U21 Doctoral Mobility Scholarship from the University of Auckland in 2016.</em></p><p><em>David Schoeman receives funding from the Australian Research Council.</em></p><p><em>Mark John Costello does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</em></p><p><em>Reposted with permission from <a href="https://theconversation.com/marine-life-is-fleeing-the-equator-to-cooler-waters-history-tells-us-this-could-trigger-a-mass-extinction-event-158424" target="_blank" style="">The Conversation</a>. </em></p>
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Herring are a primary food source for Norway's orcas. Luis Lamar / National Geographic for Disney+
Belugas are extremely social creatures with a varied vocal range. Peter Kragh / National Geographic for Disney+
A Southern Right whales is pictured in the accompanying book, "Secrets of the Whales." Brian Skerry / National Geographic