Anglican archbishop Desmond Tutu has called Alberta's oilsands "filth" created by greed, and has urged all sides to work together to protect the environment and aboriginal rights.
"The fact that this filth is being created now, when the link between carbon emissions and global warming is so obvious, reflects negligence and greed," Tutu told more than 200 rapt attendees a conference on oilsands development and treaty rights in Fort McMurray.
"The oilsands are emblematic of an era of high carbon and high-risk fuels that must end if we are committed to a safer climate."
"Oilsands development not only devastates our shared climate, it is also stripping away the rights of First Nations and affected communities to protect their children, land and water from being poisoned."
Tutu has criticized the oilsands before.
The archbishop, who won the Nobel Peace Prize for his role in the fight against apartheid, has taken strong stands on climate change and against projects such as the Keystone XL pipeline. Tutu has signed a petition against the project. In an opinion column earlier this year in the British newspaper the Guardian, the 82-year-old called the Keystone proposal to move oilsands bitumen from Alberta to the U.S. appalling.
He has also called for boycotts of events sponsored by the fossil fuel industry, for health warnings on oil company ads and for divestment of oil industry investments held by universities and municipalities, similar to measures that were brought against South Africa's old apartheid regime.
Industry supporters have pointed out that the oilsands' contribution to the amount of heat-trapping carbon dioxide produced globally in minuscule.
But Tutu argued that humanity must act together to end a threat that is already affecting people around the globe.
"This is why I have stood in solidarity with communities across Canada and the United States that are opposing the proposed oilsands pipeline," he said. "The struggle of citizens against the pipelines puts them on the front lines of the most important struggles in North America today."
Despite his uncompromising rhetoric, Tutu urged people from all sides to work together. He pointed to the experience of his own country overcoming generations of racial intolerance as an example of how widely differing positions can be brought together through mutual good will.
"Magnanimity is not a river that flows in one direction only. It is a bridge built of reasonableness and the acceptance of others that enables human beings to navigate barriers that keep us apart."
In a room tangy with the slight smell of sweetgrass, Tutu said humanity must learn to think of itself as one family.
"You can't be human all by yourself. You need other human beings to be human."
Tutu's remarks, leavened by his trademark infectious laugh, ended with the crowd on its feet while he chanted, "we are connected."