Breathe deeply, though, and you catch a whiff of fresh, hot tar. In the river, fish are speckled with shiny, wart-like blisters. And in the tiny Indian village of Fort Chipewyan, people are coming down with leukemia, bile duct cancer and other diseases.

Those who aren't physically sick are worried sick. Much of their unease is directed upstream at a moonscape of strip mines, tailings ponds and clouds of dust and gases, including climate-warming carbon dioxide.

What's being clawed from the earth there may surprise you. It's America's next tank of gas.

As reserves of crude oil tighten and gas prices soar, the quest for a backup energy source grows more heated. Already, a biofuels industry based on corn is booming. There are dreams of adding switch grass and wood chips to the mix, perhaps one day running cars on cleaner hydrogen.

In northeast Alberta, though, the race for a stand-in fuel is taking a U-turn, one in which fleets of dinosaur-sized trucks and shovels larger than two-car garages are tearing apart a rich mosaic of woods and wetlands to extract some of the dirtiest fossil fuel on the planet – more than two-thirds of which is exported to the United States to be refined into gasoline, diesel and jet fuel.

All new fuels pose environmental challenges, but Alberta's proxy petroleum is filled with them, from the destruction of migratory waterfowl habitat to rising greenhouse gas emissions and growing concerns about pollution and cancer.

Last month, a new report catalogued industrial contaminants – from arsenic to mercury to polycyclic aromatic hydrocarbons – downstream of the digging zone and concluded that more independent scientific inquiry is urgent.

Jim Law, the spokesman for Alberta's minister of the environment, disputed the report's conclusions, saying, "The development of the oil sands does not proceed at the expense of the environment." But Kevin Timoney, an Alberta ecologist and the report's author, disagreed.

"These compounds are already at levels sufficient to cause harm, (and) levels are increasing in concentration," Timoney said. "There is no logical explanation … other than industry activity."

The new Persian Gulf

The stockpile of energy under Alberta's swampy woodlands, an estimated 175 billion barrels of oil, is the largest reserve in the Western Hemisphere and the second largest on Earth, behind Saudi Arabia.

This oil doesn't slosh into a barrel like conventional petroleum. It clings to dark, gooey layers of sand and clay that look like cookie dough when dug out of the ground. Alberta's oil isn't really oil at all, but bitumen, used for canoe patching by early fur traders and more recently for road sealing and paving.

Coaxing bitumen out of sand and clay and upgrading it into synthetic petroleum is so costly and energy-intensive that for years most companies ignored the region.

When crude oil prices climbed over $50 back in 2004, however, companies began rushing to Alberta as if it were a new Persian Gulf. Today, that rush is a stampede.

The road from Edmonton to Fort McMurray – the frontier outpost where the digging starts – thunders with big-rig trucks hauling mining gear. In town, dollars flow so freely some call the place Fort McMoney. Near the airport, a billboard barks out the bonanza spirit: "We have the energy," it says.

Already, Alberta's tar sands oil field produces 1.3 million barrels a day, three times more than Alaska's Prudhoe Bay. By 2016, daily output is expected to rise to 3 million barrels, exceeding the oil production of Venezuela.

Scores of companies are active in the area, from U.S.-based Chevron and ConocoPhillips to homegrown Petro-Canada. This year, projects, expansions and acquisitions totaling more than $50 billion have been announced.

From the air, the footprint of development reveals itself in a tick-tack-toe grid of oil service roads slicing into wild country, in the silver glint of pipelines and heavy equipment.

On the ground, a sign at one of the oldest operations, Syncrude-Canada's Mildred Lake mine north of Fort McMurray, assures visitors that there is nothing modest about the place.

"Since operations began in 1978, we've moved over 1.4 billion tons of overburden," the sign reads, referring to the rock and soil over bitumen deposits. "This is more dirt than was moved for the Great Wall of China, the Suez Canal, the Great Pyramid of Cheops and the 10 largest dams in the world, combined!"

The disturbance is so extensive that the United Nations Environment Program has placed Alberta's tar sands oil field on its list of 100 hot spots of environmental change, a roster that includes the Yangtze River Valley, drowned by China's Three Gorges Dam.

"There is nothing on this planet that compares with the destruction going on there," said David Schindler, an ecology professor at the University of Alberta, Edmonton. "If there were a global prize for unsustainable development, the oil sands would be the clear winner."

Industry officials say they are working to resolve the problems, including reducing the climate-warming greenhouse gases emitted in upgrading bitumen into refinery-ready crude oil.

"It's heavy oil; it does generate more carbon dioxide in the refining process than light oil," said Greg Stringham, vice president of markets for the Canadian Association of Petroleum Producers. "But there are significant mitigative measures that can be taken."

One company has found a way to use cooler water in upgrading, consuming less energy – and emitting less carbon dioxide, Stringham said. Others are pursuing ways to capture CO 2 and store it underground.

Environmentalists, though, expect such gains to be outpaced by the rapid clip of expansion. "While they say they are bending the curve a little bit in terms of where emissions are going, they are not achieving a real reduction," said Nashina Shariff, associate director of the Toxics Watch Society of Alberta.

Among industry observers, some are skeptical.

"You put it all together and you say this isn't a solution, this is a problem," said Matthew Simmons, chairman of Simmons & Company International, an investment bank in Houston that specializes in energy research and trading.

Native people feel the pain

For local residents, the impact can be very personal.

You can hear it in the trembling of Frank Marcel's voice as he leans on a walker outside The Northern – the only grocery store in Fort Chipewyan, 100 miles north of Fort McMurray – and talks about fear in the indigenous community.

"Before the oil companies, everybody was out on the land, fishing and trapping," he said. "Today, we're even scared to eat a moose.

"People used to die of old age. This generation now, everybody seems to die of cancer."

You can see it in the pained expression on Celina Harpe's face as she describes the drum-like migraines that hold her hostage when fumes from the tar sands blow through Fort MacKay, a native village virtually surrounded by tar sands operations.

"One whiff of it and your head just starts to pound," said Harpe, a retired community health nurse. "It's so strong we have to close the doors and windows."

You can sense it in the frustration of biology professor Suzanne Bayley with the U.S. motorists who are fueling the boom.

"What bugs us the most is Americans are not really even attempting to conserve," said Bayley, who teaches at the University of Alberta, Edmonton. "Why should we destroy our environment for a thousand years for people who are on a binge?"

With 5 percent of the world's people, the United States burns 44 percent of the world's gasoline, according to the U.S. Energy Information Administration. No nation plays a bigger role in keeping America on the road than Canada, which exports around 2.2 million barrels of oil a day to the United States, roughly a third of it from Alberta's tar sands.

About the writer:

• Call The Bee's Tom Knudson, (530) 582-5336. Travel and research for this story were underwritten by a grant from the Alicia Patterson Foundation in Washington, D.C.