Canada has rejected a mine expansion project in the Arctic after years of uncertainty and fierce protest, in what community members and campaigners say is a win for the vulnerable marine ecosystem and wildlife. Baffinland Iron Mines’ planned expansion to its Mary River site would have seen it double output to 12m tonnes of iron ore. To bring the ore to market, the mine also said it needed to build a 110km railway to a port near the community of Pond Inlet as well as doubling its shipping. The company – the biggest private-sector employer in Nunavut territory with nearly 2,600 workers – has said the expansion is critical to remaining profitable. On Wednesday evening, after repeated delays, Canada’s northern affairs minister, Dan Vandal, rejected the company’s application, citing fears from Inuit groups that the expansion could have devastating effects on marine mammals, including key populations of narwhal. The region is home to the densest narwhal population in the world – an important food source for Inuit communities. That decision comes six months after the Nunavut Impact Review Board came out against the expansion. The board held in-person meetings in Pond Inlet, the community closest to the mine, as well as in the territorial capital of Iqaluit. After hearing from community members and the mine, it concluded the project could result in “significant adverse eco-systemic effects on marine mammals and fish, caribou and other terrestrial wildlife, along with vegetation and freshwater” as well as “significant adverse socio-economic effects on Inuit harvesting, culture, land use and food security in Nunavut”. The board’s review lasted four years, the longest in its history. In his Wednesday decision, Vandal wrote that he and other ministers had “carefully considered” the proposal, along with the input from Inuit groups, concluding that the project “should not proceed at this time”. Vandal said both the Qikiqtani Inuit Association and Nunavut Tunngavik Incorporated wrote to him and raised concerns about the proposed expansion, arguing adverse effects couldn’t be “prevented, mitigated, or adaptively managed under the proposed mitigations”. In his decision, the minister acknowledged the economic significance of the project, given that Baffinland’s operations make up nearly a quarter of the territory’s GDP. “However, we have taken particular note of the conclusions of the board, the designated Inuit organizations and the Hunters and Trappers Organizations … who have expressed a lack of confidence that Phase 2, as currently conceived, can proceed without unacceptable impacts,” he wrote. Many community members have said they aren’t against the mine, but worry the expansion will create irreversible damage. The decision has been met with approval from marine conservationists. “Our first reaction was relief. It was a very arduous and protracted hearing process. But in that process, communities were loud and clear. They expressed a lot of concern about this,” said Chris Debicki, a vice-president and counsel at the conservation organization Oceans North. “But there are still unresolved issues with respect to the impact of mining and shipping on the ecosystem.” Among their concerns are the effects of the iron dust from large trucks, leading to the possible contamination of sea ice. Others say they have been overlooked by decision makers in Iqaluit. Under the landmark 1993 Nunavut Agreement, which established a number of key rights for Inuit on their lands, Baffinland is required to negotiate a benefit agreement with the Inuit groups that represent residents of the territory. Jerry Natanine, mayor of Clyde River, previously told the Guardian he and others were trying to form a new group that would have the power to negotiate royalty payments and have greater say over projects that could affect their communities. In February 2021, a group of hunters blocked access to the mine in protest, braving frigid temperatures for nearly a week. Seven hunters, some of whom travelled from Clyde River, used snowmobiles and sleds to block the airstrip and service road to the Mary River Mine as temperatures dipped to -30C (-22F). “The decision comes from years of disappointment from Inuit organizations that don’t look out for our behalf,” Natanine said at the time, adding that hunters are forced to “fight for their culture and their way of life” when projects are imposed on them. Baffinland, jointly owned by ArcelorMittal and the Houston private equity firm the Energy and Minerals Group, had previously tried to ease concerns over the project, saying it is confident wildlife will not be affected by increased ore shipments. The company has also touted more than C$2bn (US$1.5bn) in royalties paid to Inuit over the mine’s 30-year lifespan. The company was expected to issue a statement on Thursday in response to the federal government’s decision.