Massive Canadian mines pose transboundary risks
Science Magazine In 2019, Canada approved an extension of the deadline to start one of the world’s largest copper and gold mines in the headwaters of the transboundary Unuk River ( 1 ). The plan for the Kerr-Sulphurets -Mitchell (KSM) mine is to dig one of the largest human-made holes on earth, erect one of the highest dams in North America, and operate water treatment for 200 years after the mine closes ( 2 ). Mines such as KSM pose long-term risks to downstream water quality, fish, and people ( 3 ). Given that mine contamination is not constrained by political boundaries, U.S., Canadian, and Indigenous governments must urgently engage in collaborative evaluation and regulation of mines in internationally shared rivers. Shortfalls in mine assessments and permitting policies should be addressed. Mine assessments underestimate risk at high environmental cost. Contributing factors include the ecological complexity of rivers, policy shortcomings in weighing environmental risk