The purpose of Keystone XL is to bring tar sands crude oil through the United States to Gulf Coast refineries. The route through the United States is actually the oil industry's second choice: Transporting the oil west from Alberta to the Pacific Coast would be shorter and much cheaper, but Canadians concerned about environmental impacts and threats to native people's lands are challenging that route, and with good reason. The existing and potential environmental impacts along the 2,000-mile pipeline route are profound.

In Canada, extraction of tar sands crude requires clear-cutting thousands of acres of boreal forests, diverting rivers, strip-mining, and destroying critical habitat for some of the largest populations of woodland caribou left in the world. Thirty percent of North America's songbirds and 40% of its waterfowl rely on the wetlands and waterways of the boreal forest.

Tar sands oil production has already created more than 50 square miles of toxic waste ponds so massive they are visible from space. Even more important, tar sands oil extraction produces three times more greenhouse gas emissions than conventional oil and gas, putting even greater strain on our atmosphere and oceans, which have little absorptive capacity left.