The oil sands, which would feed the Keystone XL pipeline, have created thousands of jobs in Canada’s Alberta province, and the extraction industry has tripled in size since 1995. Government estimates say the country may double its current output of heavy crude by the end of this decade. But some researchers and residents are concerned Alberta’s economic engine is exacting a heavy environmental toll.

Correspondent Michael Davie explores how oil-sands production is changing Alberta, and speaks with industry supporters about the economic benefits and with industry critics who say it’s harming the air, water, and wildlife.