Canada's Mackenzie river valley is again being explored, as, more modestly, is its less promising Arctic offshore.

ECONOMIST: Resources: Hidden treasure | The

In 2006, a pack of six Mackenzie River wolves - a North American wolf - were put down because they were "not portraying their natural behaviour".

BBC: Pup and mother Elara

Strel plans to swim across the Grand Canyon , along 1, 000 miles of the freezing Mackenzie River in Canada, and the length of the 2, 000-mile Volga .

BBC: What adventures are actually left?

Such is the demand for natural gas around Fort McMurray that a consortium of companies, including Shell Canada and Imperial Oil, has proposed building a seven-hundred-and-fifty-mile pipeline from the Arctic Ocean through the largely undisturbed wilderness of the Mackenzie River Valley and down into northern Alberta.

NEWYORKER: Unconventional Crude