I was first introduced to the tar-sands phenomenon via a National Geographic article from 2009. A spruce-covered wetlands along the Athabasca River in northern Alberta, Canada - a landscape not hugely dissimilar from our own -had been turned into something closely approximating the Western conception of hell.

The land was gouged and barren, in some places 100 feet of soil and organic matter skinned away, leaving an oily black vista stretching to the horizon. As desensitised as I'd become to images of environmental damage, this one shocked me on a visceral level.

It's been called "the world's dirtiest fuel" and until recently, tar-sand deposits were considered too expensive and too destructive to mine. Today, as the price of traditional oil rises and technology makes profitable extraction more viable, the vast tracts under Canada, and smaller deposits in Russia, Kazakhstan and the Congo are considered part of our global oil reserves.

The tar sands industry would like to see its activities rebranded into the sexier "oil sands", which implies something more palatable to the public.

However, it's a dirty, sticky business: tar sand is a naturally occurring bitumen deposit, a semi-solid sludge of heavy crude oil mixed with sand and clay.

Because it doesn't flow, the industry uses strip mining for extraction, rather than traditional oil wells, and then melts the oil out of the sand, generally with steam. It takes two tonnes of sand, and five barrels of water, to produce a single barrel of oil - with the wastewater going into "tailings ponds" for decontamination. Coated with rafts of floating bitumen, these ponds are so toxic that they kill birds that land on their waters.

The process produces three times the greenhouse gas emissions of conventional oil, and it's these emissions, specifically, that mean Canada will not meet its Kyoto reduction commitments. "The world's largest and most devastating industrial project is situated in the heart of the largest and most intact forest in the world - Canada's Boreal Forest," said photojournalist Garth Lenz in his 2011 TED talk.

Lenz, too, has documented the one-sided battle between untouched landscape and heavy industry, producing an exhibition on the Alberta tar sands titled The True Cost of Oil. Wetlands, says Lenz, are the most endangered, but critical ecosystems: "They clean air, they clean water, and they sequester a large amount of greenhouse gases. They're also home to a huge diversity of species."

The vast lakes of contaminated tailings wastewater and massive infrastructure of the Athabasca River facilities already constitute the biggest industrial project on the planet. Plans were recently announced that it is set to triple in size over the next two decades, despite warnings from scientists that the nearly 200sqkm of toxic wastewater pose the biggest threat to the environmental heartland dubbed "Canada's Serengeti".

This despite the report released by Canada's Energy Resource Conservation Board last month that found tar sands companies - including Suncor, Syncrude and Albian Sands, a consortium of Shell, Chevron and Marathon Oil Corp - have failed to meet their own commitments to implement the water recycling and reclamation plans which were a condition of licensing the land.

A recently uncovered Canadian Government memo says federal government scientists have discovered evidence that tar-sands tailings are leaking into the groundwater, contaminating lakes 100km away.

In May this year, the Canadian Department of Natural Resources doubled its spend to $16.5m on advertising to promote the Alberta tar sands, as its Prime Minister Stephen Harper arrived on American soil, part of an insistent lobbying push which aims to win White House approval for the Keystone XL pipeline extension, which could see 1.1 million barrels of oil transported to refineries in the Gulf Coast area. While there is yet to be a reliable sign as to which side of the argument Obama will take, media pundits are calling Keystone XL the most important environmental decision of his presidency.

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