By a single vote, the U.S. Senate failed to fast-track the approval of the controversial Keystone XL pipeline last week, which would carry Canadian tar sands oil straight across the nation to the Gulf of Mexico. Lawmakers are expected to approve it in January, however, and President Obama may or may not let it squeak through.

A new photo series traces the path of the proposed pipeline, from the tar sands in Alberta to massive refineries in Texas. The photos make something clear: With or without the pipeline, huge amounts of tar sands oil are already being extracted and flowing into the U.S. Over the last four years, the amount of Canadian crude sent to Texas has increased by 83%.

Photographer Alex MacLean first flew over Alberta last winter, taking shots of a post-apocalyptic landscape that are hard to capture from the ground.

Meandering Channel of Wastewater, Suncor Mine, Alberta, Canada

Strip mines cover an area of forest seven times larger than Manhattan. Since most of the tar sands are buried deep underground, and the molasses-like bitumen is too thick to extract on its own, the oil companies have also built enormous boilers to liquefy the sludge.

“Looking at the pictures of the huge furnaces they have to use in the wells, you can see how much energy this takes to extract,” says MacLean. “If you’re driving around with this fuel, it’s 17% to 20% more carbon intense than regular gas.”

MacLean returned to the oil fields again last summer with journalist Daniel Grossman (with funding from the Pulitzer Center on Crisis Reporting and Indiegogo), and then traveled on to refineries in the Midwest and the Gulf Coast that are already processing tar sands oil.