CANADIANS have rallied round Fort McMurray, the western city ravaged by a forest fire this month. They have sent food, clothing and messages of support to the 90,000 people who fled their homes. The Red Cross collected C$54m ($42m) in a matter of days. Justin Trudeau, Canada’s prime minister, promised federal help.

But the disaster has also exposed divisions between oil-producing Alberta, where more than 220,000 hectares (550,000 acres) were engulfed by fire, and the rest of Canada. The rancour appeared first on social media, with tweets such as “Welcome to climate change, Alberta. Feel free to keep denying it.” “Scumbag” was one Albertan response. The spat spread to newspapers and television. Asked at a news conference whether he blamed climate change for the fire, Mr Trudeau dodged the question.

He cannot avoid the argument which the fire has reignited. Fort McMurray makes its living from Alberta’s Athabasca tar sands. Although scientists can never be sure that climate change caused a particular event such as the Alberta fire, few people doubt that producing Athabasca crude emits more greenhouse gas than conventional oil. When oil prices were high, Fort McMurray and Alberta prospered, spurring Canada’s economic growth. The price drop has hit the region’s economy hard. Alberta is in its second year of recession; the province is likely to have a record budget deficit of C$10 billion this year. After the fire forced firms near Fort McMurray to suspend production, economists revised down their forecasts for Canada’s growth in the second quarter this year.

What Albertans want, far more than help from the Red Cross, is pipelines to carry crude oil to world markets. The province now sells nearly all its oil to the United States, which pays too little, Albertans grumble. Barack Obama has blocked the Keystone XL pipeline (see map), which would have made transport cheaper. Albertans’ hopes now rest on three other proposed conduits. Energy East, a 4,500km (2,800-mile) pipeline, which is already partly built, would carry crude to the Atlantic coast. Northern Gateway and Trans Mountain, which would run alongside an existing line, would pipe it to the Pacific. All three need the approval of the federal government and its regulator, plus support from aboriginal groups and the provinces through which they would pass. Many places have objections.