Chiefs from 28 haus tambarans – “spirit houses” – representing 78,000 people along Papua New Guinea’s remote Sepik river have formally declared they want a proposal for the country’s largest ever mine halted. PanAust, an Australian-registered miner ultimately owned by the Chinese state-owned Guangdong Rising Assets Management, has proposed building a gold, silver and copper mine on the Frieda river, a tributary to the Sepik. The mine would be the largest in PNG’s history, and one of the largest in the world, covering 16,000 hectares, and is forecast to yield gold, silver and copper worth an estimated US$1.5bn a year for more than 30 years. Haus tambarans are the cultural and political hub of villages in the Sepik region. Pre-colonisation their function was analogous to a local parliament, where debates were held and collective decisions taken. But they also play important roles in spiritual and ancestral connection and in rituals and initiations. In an unprecedented move, the 28 haus tambarans issued a collective Supreme Sukundimi Declaration calling for “a total ban on the Frieda river mine”. It said: “The river is the life of the Sepik and therefore it must be protected at all cost. It is our innate role to guard the river from exploitation and destruction by outsiders. Our future is in peril from this proposed mine and, therefore, we have gathered together as guardians of the river to stand firm as one.” In its environmental impact statement for the Frieda river mine, PanAust said the “nation-building project … presents broad commercial and socioeconomic development opportunities for Papua New Guinea”. PanAust said it had engaged in “extensive and ongoing engagement … over several decades” with those affected by the mine, running information sessions in nearly 140 villages, attended by more than 18,000 people. “Local opinions and issues have been sought through engagement campaigns … formal and informal meetings with village leaders, and through socioeconomic surveys conducted in villages between 2010 and 2018,” the company said in the statement. The mine plan also includes a hydroelectric plant, power grid, and road, airport and seaport upgrades. In March, campaign group Project Sepik and the Centre for Environmental Law and Community Rights (CELCOR) submitted several expert reports to the PNG government’s Conservation and Environment Protection Authority (CEPA), arguing the mine’s environmental impact statement was deficient because it lacked critical information about a tailings dam, analysis on the probability and consequence of a dam break, and settlement plans for displaced villages. Mine campaigner Emmanuel Peni told the Guardian PanAust had not been “honest or transparent” in its consultations with those who live in the Sepik river valley. He said people whose lives and livelihoods depended on the river feared their villages could be permanently damaged or destroyed by the mine, citing the case of Rio Tinto’s Panguna mine, which has left downstream villages with poisoned water, polluted fields and a ruined river valley. “If the dam collapses it will be catastrophic and destroy the Sepik river and our way of life,” he said. “We need to ensure that the Sepik is protected. It is our identity, our life, and the heartbeat of our culture. A life without the Sepik river as we know it would devastate our communities forever.” Peni, from Korogu village on the Sepik River, said the villages felt the need to make the collective declaration – admissible in court – because “they do not trust the government, the police, the army and the outsider who is the owner of the Frieda mine”. Peni said villages along the Frieda and Sepik rivers would seek to halt the mine through legal and legislative channels but would ultimately defend their ancestral lands. “There will be an uprising in the Sepik region and lives will be lost. No one will win this uprising. The government of PNG will have blood on their hands.” The Guardian put detailed questions to PanAust regarding its community consultation process and environmental impact statement. The company said: “PanAust remains committed to working with its communities, the government of Papua New Guinea and other relevant stakeholders to fulfil its statutory requirements and obtain the necessary permits to progress the Frieda river Project.” PanAust said it declined to comment further.