A bill to begin construction of the controversial Keystone XL pipeline, a 1,179-mile-long method of delivering oil from tar sands in Alberta to the Gulf of Mexico, was defeated in the Senate 59 to 41 today. The defeated plan would have transported 830,000 barrels per day of an oil-based substance called bitumen.

Canada has the third-largest oil reserve worldwide, according to a report in The New Yorker. The US imports more oil from Canada than any other nation, and 99 percent of Canadian oil is refined in the U.S.

Since 2008, the plan for the pipeline has been met with outcry from environmental groups, ranchers in the American West, and Native American groups, with one South Dakota Sioux tribe declaring the pipeline an "act of war," according to The Guardian.

Production from oil sands is dirty; carbon emissions from oil-sands production are predicted in 2020 to be triple the level they were in 2005, even though the US and Canada are currently trying to lower greenhouse gases, according to an editorial in the journal Nature. Its authors call for a halt on oil sand development until both nations determine how best to lower emissions. They're not alone. Many researchers, including former NASA climate scientist James Hansen, have said they consider the pipeline harmful to the environment.

Proponents of the pipeline, including Mary Landrieu, the Democratic Senator from Louisiana, have focused on the possibility of new jobs, increased tax revenue and the prospect of not needing as much foreign oil. The plan was "unlikely to significantly affect the rate of extraction in oil sands areas," according to a report from the US State Department in January. The House passed the legislation on Friday.