Smoke Crosses the Border, Tariff Threats Follow as Scientists Reject Trump’s Canada Claims

U.S. President Donald Trump has blamed Canada for wildfire smoke spreading across large parts of the United States, describing the air as being “poisoned” and suggesting Ottawa could be required to pay damages or face additional tariffs.

Trump said he raised the issue with Canadian Prime Minister Mark Carney while the two leaders attended the World Cup final in New Jersey. He said Canada needed to stop the smoke from crossing the border, adding that the United States could offer assistance but might also seek compensation or use tariffs as leverage.

The president had previously accused Canada of “wilful negligence” in managing its forests and argued that the cost of dealing with the resulting air pollution should be added to existing tariffs on Canadian goods. As of publication, however, no separate tariff measure specifically targeting wildfire smoke had been formally announced, and it remained unclear what legal authority could be used to impose one.

Trump’s comments followed several days of heavy smoke drifting from hundreds of fires in northern Canada into the U.S. Midwest and Northeast. Air-quality warnings were issued in states including Michigan, Ohio, Illinois, New York and Indiana, while several Canadian and American cities experienced unhealthy and hazy conditions.

The rapidly changing figures illustrate the scale of the emergency. On July 9, the Canadian government reported 796 active wildfires and approximately 1.4 million hectares burned since the beginning of the season. By July 24, more recent estimates indicated that the number of active fires was approaching 1,000, with approximately 3.3 million hectares affected.

Climate scientists and wildfire specialists have rejected attempts to attribute the crisis solely to poor Canadian forest management. They say rising temperatures, prolonged drought and increasingly dry vegetation are allowing fires to spread more rapidly, burn more intensely and become harder to contain.

Research published in Nature Communications supports that assessment. A study examining Canada’s record-breaking 2023 wildfire season found that human-driven climate change enabled prolonged periods of extreme fire weather. Average temperatures during the May-to-October fire season were approximately 2.2 C above the 1991–2020 average.

Experts acknowledge that forest management remains an important part of reducing risk, particularly near communities. Prescribed burning, fuel reduction and fire-resistant development can help protect populated areas. However, they say such measures cannot prevent every fire across Canada’s enormous and often inaccessible boreal forests, many of which have no road access or nearby firefighting resources.

The Canadian government says it has invested about C$12 billion in forest sustainability and wildfire prevention since 2020. Additional federal funding has been directed toward aerial firefighting capacity and fire-management programs, while Canadian officials have emphasized the long history of cross-border cooperation with the United States during wildfire emergencies.

Carney has responded that the United States could do more to address climate change, while stressing Canada’s investments in clean energy. Ontario Premier Doug Ford also rejected the criticism, pointing to Canada’s support for American communities during previous U.S. wildfire disasters.

The dispute shows how wildfire smoke has expanded from an environmental and public-health emergency into another political and trade issue between Washington and Ottawa. Scientists warn, however, that tariffs and blame will not stop smoke at the border. They argue that the worsening threat requires cross-border cooperation, stronger prevention and emergency-response capacity, and long-term action on the climatic conditions driving increasingly severe fires.