By Bryan Walsh
November 14, 2014

The proposed Keystone XL pipeline has become the single most important environmental issue in the U.S.—even though its environmental impact may not even be that great. The pipeline would move some 830,000 barrels of crude a day from the Canadian oil sands in Alberta to Steele City, Nebraska and then down to the Gulf of Mexico. Keystone would make it easier for Canadian producers to sell their landlocked crude to the rest of the world—which is exactly what environmentalists fear. Oil sands crude is dirtier and has a bigger carbon footprint than conventional oil.

Landowners in Nebraska worry that a spill could contaminate the state’s vital aquifer, while environmentalists fear that the pipeline will speed the development of the oil sands and help add huge amounts of carbon into the atmosphere. But other experts argue that oil sands crude will come to the U.S. by another route—most likely through rail—or be sold elsewhere in the world if Keystone isn’t built, meaning the planet won’t be any better off.

Since it’s an international project, the President has to sign off on the Keystone pipeline before it can be built—and much to the consternation of the oil industry, President Obama has delayed his decision for years, claiming that he needs more time to study the pipeline. But with Republicans now firmly in charge of both houses of Congress—and many conservative Democrats in favor of the project—Obama may need to make a decision soon.

With a decision potentially on the horizon — the House passed legislation on Friday and the Senate is expected to vote on the topic next week — refresh your understanding of the debate with these three articles from the TIME archives:

Mar. 12, 2012: Cold Warrior

A profile of activist and author Bill McKibben explains why the pipeline extension drew environmentalists’ attention, and how they helped influence President Obama’s decision to reject a 2012 version of the application to build the pipeline:

Apr. 9, 2012: The Truth About Oil

A broader look at new sources of oil explains why the crude that would travel through the pipeline is different from other oil:

Jan. 31, 2014: Report Raises No Major Climate Objections to Keystone Pipeline, But the Choice Is Obama’s

After the President’s initial rejection of the pipeline proposal due to insufficient information, the State Department spent the next few years putting together an assessment of its potential environmental impact. The finding, released early this year, was disappointing to environmentalists: that whether or not the pipeline was built, about the same amount of oil would be produced.

Read more of TIME’s science coverage in the TIME Vault

Contact us at editors@time.com.

SPONSORED FINANCIAL CONTENT

Read More From TIME

EDIT POST