US President Donald Trump has threatened to impose additional tariffs on Canada in response to the thick blanket of wildfire smoke blanketing large swaths of the northern United States, accusing Ottawa of failing to manage its forests and calling the cross-border air pollution an act of "willful negligence." In posts on social media, Trump declared that the "cost" of the pollution would be added to existing tariffs on Canadian exports, framing the environmental crisis as a bilateral grievance rather than a shared natural disaster.
The threat comes as Canadian authorities battle nearly 900 active wildfires, more than 190 of them in the province of Ontario, where Premier Doug Ford confirmed that dozens remain out of control. The fires have been devastating in scale — nearly three million hectares of Canadian land have already been destroyed — and their effects have spread far beyond the border. Cities including Detroit, Chicago, Washington DC and New York have recorded hazardous air quality, with Detroit ranking as the worst city in the world for air quality on Friday according to the Swiss monitoring platform IQAir. Outdoor events have been cancelled across the northern US, airports have reported delays due to low visibility, and health officials have urged residents to stay indoors.
Trump said he would call Canadian Prime Minister Mark Carney to demand an explanation, accusing Canada of refusing to engage in "basic Forest Management and Debris Removal." Fellow Republicans amplified the criticism, with several US lawmakers from Michigan writing an open letter warning that their "patience has run out" and raising the possibility of direct US involvement in cross-border firefighting. Some Republicans also renewed calls for Canada to become the 51st US state, a suggestion that has repeatedly provoked anger in Canada. Ford pushed back firmly, noting that Canada has helped the US battle wildfires in California and respond to hurricanes, and called on American counterparts to "send support, send help" rather than complaints. Canada's emergency management minister pointed to a reciprocal firefighting agreement dating to 1982 and noted that Canada has invested roughly C$12 billion in forest sustainability and fire prevention.
Scientists are broadly skeptical of Trump's framing. Experts from the University of Toronto and the University of Waterloo noted that wildfire smoke travels wherever winds carry it regardless of national borders, and that smoke from major US wildfires has also affected Canada in recent years. The current fires are driven largely by sustained heat and below-average rainfall across northern Ontario in late June — conditions that researchers link in part to climate change, which is creating hotter, drier landscapes across the continent. "Climate change is a global issue, and it would be inaccurate to suggest that Canada alone caused or could have prevented these wildfires," said Dr Anabela Bonada of the University of Waterloo.
The episode underscores the deep tension in the US-Canada relationship since Trump returned to the White House in January 2025 and imposed sweeping tariffs on a country that had previously enjoyed decades of largely tariff-free trade with its southern neighbour. Critics noted an additional irony: the New York Times reported on Friday that the Trump administration had cut funding for wildfire research, including laboratories studying the health effects of wildfire smoke — the very problem Trump is now invoking to justify new economic pressure on Canada. The wildfire crisis has also cast a shadow over Sunday's FIFA World Cup final, which is scheduled to take place in New Jersey amid lingering concerns about air quality.