Mining negatively affects fish populations across North America

A new study published in the journal Science Advances has synthesized the impact of metal and coal mining on salmon and trout populations in North America. This first comprehensive effort to link mining policy to our current understanding of watershed ecology and salmonid biology highlights the urgent need for better and more transparent scientific accounts of the effects on certain fish species, in order to inform current policies.   

“Our paper is not for or against mining, but it does describe current environmental challenges and gaps in the application of science to mining governance. We believe it will provide critically needed scientific clarity for this controversial topic,” said study lead author Christopher Sergeant, a doctoral student at the University of Alaska Fairbanks College of Fisheries and Ocean Sciences (CFOS).

By integrating and reviewing data on hydrology, river ecology, aquatic toxicology, biology, and mining policy, Sergeant and his colleagues built detailed assessment maps of over 3,600 mines across Washington, Montana, British Columbia, the Yukon, and Alaska.

The results revealed that despite impact assessments aiming to evaluate risk and inform mitigation strategies, mines in North America continue to harm salmonid-bearing watersheds through various contaminants, streamflow alteration, and stream channel burial. For instance, heavy metals may alter salmons’ sense of smell, affecting their ability to escape predators and find their way back from the ocean to spawn, while silt can suffocate salmon eggs, impeding embryos’ ability to survive contaminated groundwater.

“Not all mines pose the same level of risk, but our review revealed that harm from mining can be severe and long-lasting. The extent of mining pressures on these watersheds underscores the importance of accurately assessing risk to water, fish, and communities,” said Sergeant. 

According to the researchers, mining policies fail to properly account for the breadth and duration of the environmental impacts.

“The crux of the issue is that salmon use so much of the watershed during their life cycle. They move throughout watersheds, whereas the impact assessments of mining projects tend to be very locally focused, and they don’t sufficiently consider all of the compounding and downstream effects of mining,” explained Megan McPhee, an associate professor of Fisheries Genetics, Ecology, and Conservation at CFOS.

The researchers conclude by identifying four key issues that will be foundational to modern, science-based risk assessment and mitigation of mining activities: understanding stressor complexity and uncertainty, accounting for the cumulative effects of activities across a mine’s life cycle, developing realistic mitigation strategies, and taking into account the potential of climate change to magnify risk.

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By Andrei Ionescu, Earth.com Staff Writer