The Obama administration has decided to reject the Keystone XL pipeline project, which, if completed, would have carried massive amounts of petroleum from Canada through to the Gulf Coast. In an announcement, President Obama cited the effects of global climate change in making the decision, and said that the shipments through the United States "would not increase America's energy security."

The pipeline has proven deeply controversial, as for seven years, the project has been cast as either a willful environmental tragedy, or a necessary plan to create jobs. Although the relative environmental and economic effects of the pipeline have been hotly debated, the pipeline has taken on an outsized symbolic importance since it first came under review. It's also created a deep split among politicians over climate policy, with President Obama previously vetoing a measure that would have sped up a review of the pipeline.

The project would have transported hundreds of thousands of barrels of oil daily, as it crossed six states on its 1,700-mile route, but environmentalists have argued that the project would be an unreasonable contributor to climate change. President Obama had previously suggested that he agrees with that view.

In his announcement, Obama strongly disagreed with the notion that the economy would be a harmed by the project's rejection, instead using the moment to make a call for a focus on climate policy. "Today we're continuing to lead by example," Obama said.