What new mining projects could mean for Alaskan salmon

What new mining projects could mean for Alaskan salmon

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This article was originally featured on Undark.

Wild Alaskan Salmon are the gold standard in American seafood. The long journey from river to ocean and back creates the muscle mass that gives salmon its unique texture and flavor. Clean rivers in the north produce seafood with very low levels mercury and other contaminants. Indigenous communities have been harvesting salmon in Northwestern North America for more than 10,000 years and some still depend on subsistence fishing for survival. In southeastern Alaska, salmon fishing and processing adds an annual total of about $70 million to the local economy.

But 21st-century salmon face many stressors, including habit loss, climate change, and overfishing. As a result, salmon populations are declining across the United States. The fish still thrive in some parts of Alaska, but local residents and scientists are increasingly concerned about an additional stressor: the mining industry. The transboundary region of southeastern Alaska, British Columbia, which includes three major salmon-bearing river systems, is home to active and proposed mines as well as dozens of exploratory projects. One of these proposed mines, the Kerr-Sulphurets-Mitchell project in Canada, will extract ore from what is reportedly the largest undeveloped gold-copper deposit in the world.

Scientists have sought to understand the effects of mining on salmonids for decades. This family includes trout, salmon, and other closely related fish. In July, the journal Science Advances published a review study evaluating more than 100 research papers and documents, concluding that the earlier research has underestimated the impacts of mining operations on Pacific salmonids. The authors stated that mining activities are of particular concern today because of the rising demand for metals by manufacturers looking for low-carbon technologies such as electric cars.

Mining can cause contamination in nearby watersheds that could pose a threat to salmon’s health. After the extraction of ore, mine tailings, which is the slurry of silt and fine sand, clay, as well as water, must be stored safely. Scientists warn that current and future mining activities could have severe consequences for Alaskan salmon and their watersheds if they are not properly mitigated.

In interviews with Undark, many mining representatives highlighted the industry’s efforts in keeping watersheds clean. Many scientists and locals remain skeptical and worry about the loss of salmon in the region. The nonprofit Salmon Beyond Borders was created to protect transboundary rivers and ways of life. Heather Hardcastle, a campaign advisor for the organization, stated that wild salmon are “at the center” of her life.


Northwestern North America represents a convergence of natural resources, wrote the July paper’s 20-plus authors, most of whom are affiliated with the region’s universities, First Nations, or environmental nonprofits. Northwestern North America has large reserves of metals and coal. The area is also home to some of the most productive and least-disturbed salmonid habitats on Earth, according to the authors. These fish are unique because of their large home ranges, and their tendency to use every part of the watershed. It can be difficult to assess the risks of mining and to mitigate them.

The review was thorough and included not only peer-reviewed studies but also government databases, reports, industry disclosure documents, and technical materials. The review revealed that mining operations often fail to meet their water quality goals. A few studies have not compared the industry’s actual and predicted impacts on mining. The cumulative effects of multiple mining operations and other stressors is often underestimated. Mitigation strategies don’t always use proven technology and they often overlook the impact of climate change over the coming years.

Chris Sergeant,

Lead researcher, said that the July paper is the first to review and summarize the impacts of mining on salmon and offer guidance on how to improve science that supports mining policy. Researchers were able to see the big picture because of the size of the review. This is especially important when data comes directly from mining companies.

Northwestern North America holds substantial reserves of coal and metals. It is also home to “some of the most productive and least disturbed salmonid habitat remaining on Earth.”

“It’s almost impossible with the data we get from mining operations these days, to do a type of pre-project evaluation of risk,” Sergeant stated. Sergeant said that he was not surprised by his paper’s findings because there are so many examples of how mining operations can impact watersheds. The extent of the problem is made clearer by having all these examples in one place.

Jonathan Moore is a professor at Simon Fraser University, British Columbia, who contributed to the July review. He noted that salmon can also support the health of local watersheds. More than 100 species are believed to have some kind of relationship with salmon, whether direct or indirect. For example, trout eat young salmon eggs, while bears eat spawning adults. When salmon die, their bodies contribute nutrients like nitrogen and phosphorus to the watershed and the forests that grow nearby.

The ecological effects of these nutrients can sometimes be seen to the human eye. A 2021 study found that the “greenness” of vegetation along the lower Adams River in British Columbia increased in the summers following a productive sockeye salmon run. Another study found that the presence of dead salmon in spawning grounds influenced the growth rate of Sitka spruce trees not just close to the riverbank but also farther into the forest, where researchers said “bear trails and assumed urine deposition were prevalent.”


Scientists and environmental activists are concerned about new mining projects. This is partly because of the fact that mining disasters still happen despite modern infrastructure being strong enough to prevent them. During a 2014 dam failure at the Mount Polley Mine in British Columbia, for example, 32 million cubic yards of wastewater and mine tailings spilled into a nearby lake. The mine waste then traveled down a creek to a second lake which is home to one of the most important salmon habitats in the region.

Imperial Metals, a mining company, maintains that the Mount Polley tailings did not cause significant environmental damage. C.D. wrote that the tailings contained very few pyrite, which is a mineral that can produce sulfuric acid when it is exposed to water and air. In an email to Undark, Anglin, who was the company’s chief scientist officer after the Mount Polley accident wrote that the tailings contained very little pyrite. Sulfuric acid is one of the most environmentally concerning consequences of mining. The compound can cause damage to waterways and threaten the survival of fish and other wildlife. It can also dissolve other heavy metals such as lead and mercury in the rocks it comes into contact with. Anglin stated that the Mount Polley tailings were considered chemically benign .”

Still, a 2022 study found that the dam failure did have environmental consequences. Gregory Pyle, a researcher from the University of Lethbridge, Alberta, Canada, led the study. It was not included in the July review. Pyle and his team collected water, sediment, as well as invertebrate samples at the affected areas and Bootjack Lake, which was not affected by the spill. Pyle’s team discovered elevated copper levels in sediments from the worst affected areas, as well high copper concentrations in the bodies and invertebrates that live in these areas. The researchers also found elevated copper levels at Bootjack Lake, suggesting that the environmental effects of Mount Polley’s mine predate the spill.

Anglin claimed that the study’s results were misleading. “While copper levels are slightly higher in some organisms in unimpacted regions,” she wrote, “they’re not at a level .”

of environmental concern.”

Pyle disagrees. In an interview with Undark, he pointed to a follow-up study in which his team exposed freshwater scuds (a shrimplike mollusk) to contaminated and uncontaminated water and sediment collected four years after the Mount Polley spill. “When they were in contact with the sediments for as little as 14 days,” he said, “it impaired their growth and survival.” The results of Pyle’s study have implications for salmon since scuds and other invertebrates are an important food source for these fish.

Copper can also build up in the bodies of salmon, as well as their prey, impacting their growth and survival. Studies have found that even sub-lethal copper levels can harm salmon’s olfactory system, which may make it harder for them to avoid predators and orient themselves in their habitat. Moore said that copper has insidious effects on salmon’s navigation abilities. “Salmon might not find their way home if there is too much copper ,” Moore said.

Scientists say that even if contaminants are removed from the equation, the sheer volume in the watershed after a spillage like the one at Mount Polley could have serious physical consequences. Moore said that “these big disasters like Mount Polley transform these systems.” The slurry of fine sediments and other waste materials can cover gravel where salmon might otherwise lay eggs, rendering it unusable as a spawning habitat.

The lingering effects of past mining have activists and scientists concerned about new projects like the proposed Kerr-Sulphurets-Mitchell mine, which is expected to begin construction in the summer of 2026. Hardcastle stated that Salmon Beyond Borders would like the region to adopt a cautious approach to new mining projects.

“What’s all the fuss about trying to decarbonize the energy sector and move to a cleaner future?” she asks. “If all we do is swap big oil and the fossil fuel industries for big mining ?”


Christopher Mebane is the assistant director for hydrologic research at the U.S. Geological Survey. He studies metals, toxicity and mining and jokes that he is a “dirty water biologist.” The July study, which he was not part of, was “a fair assessment” about the dangers that mining activities pose to salmonids. He said that he could not find any errors or misstatements. “But you know, if this were written by a group of mining engineers, it would have a very different tone and probably conclusions.”

Indeed: Representatives of the mining industry say that the mistakes made in the past will not be repeated. Michael Goehring, president of the Mining Association of British Columbia (a trade group), stated that mines with tailing storage facilities must implement new design criteria and operational criteria using best-available technology. Brent Murphy, senior vice-president of environmental affairs at Seabridge Gold (the company that will operate KSM’s proposed mine), said that the KSM tailings management facilities won’t flow into Alaskan waters. Although the mine itself will be located in a watershed that drains into a transboundary river, Murphy said the tailings facility will drain only into Canadian waters and does not require water treatment.Salmon are believed to have a relationship, direct or indirect, with more than 100 different species. Brown bears in Alaska are known to fish for salmon adult as they swim upstream to spawn. Visual: RooM via Getty Images

Murphy said that the tailings facility would be located in a confining valley and will be closed off by two large dams. “We’re containing all of the potential acid-generating material, which is only 10 percent of the total volume of the tailings produced, within a lined facility,” he said. This area will be surrounded with more than 1.8 miles compacted sandy material. Murphy stated that Murphy’s design was intended to address concerns of First Nations.

To address community and agency concerns over the long-term, mining operations might also propose water treatment plans that extend for centuries. Seabridge Gold said water treatment will continue for 200 years after the KSM mine closes, though Murphy told Undark that the water at the site is already naturally contaminated with copper, iron, and selenium and won’t be further contaminated by mine operations.

Christopher Sergeant led the July review and said he was skeptical. “I don’t know of any successful examples of anyone treating water for 200 years,” he said. “And my understanding about corporate structure is that there isn’t really a motivation once a project isn’t creating profit anymore.” That’s a big concern of mine: Who is going to be on the hook for making sure that that water is treated in what’s basically perpetuity?”

Goehring stated that the cost of ongoing water treatment can be paid upfront. He said that British Colombia already has 2.3 billion Canadian dollars ($1.7billion) in its mining industry to contain mine waste. He said that this ensures that, after the KSM mine closes down, water treatment will continue .”

“Who is going to be on the hook for making sure that that water is treated in what’s basically perpetuity?” said Sergeant.

The future effects of climate change may threaten infrastructure at KSM, and other mines. “A lot of the calculations that are made for engineering are based on what the current environment looks like,” said Sergeant, adding that there’s really no way to predict how different the environment will be 10 or 20 years into the life of a mine. He noted that destructive weather events are becoming more common and “aren’t necessarily considered” in engineering designs .”

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For now, Salmon Beyond Borders and other environmental groups are trying to convince policymakers and agencies to halt the expansion of new and existing mines in shared watersheds. Until Canadian law is amended to include provisions for downstream parties, Salmon Beyond Borders also called for a permanent ban of tailings dams in the vicinity of transboundary rivers. Permanent bans are not practical or feasible because of the lucrative nature of mining.

Moore stated that the July paper highlights the key challenges in protecting salmon populations in a region dominated by the mining industry. He said that he hopes the research will lead to “a productive path forward” in which the mining industry and salmon systems can coexist with the communities that rely on them.


UPDATE – An earlier version of this article incorrectly stated that the KSM tailings disposal facility would be located in a watershed which drains into a transboundary stream. The wastewater will then be piped to a treatment plant miles away. The mine is in such a watershed. However, the tailings management facility does not drain into Canadian waters. Heather Hardcastle was originally the campaign director for Salmon Without Borders. She is a campaign advisor.

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