In the United States, the tar sands debate focuses on Keystone XL, the 1,200-mile pipeline that would link Alberta oil to the Gulf of Mexico. What is often overlooked is that Keystone XL is only one of 13 pipelines completed or proposed by the Harper government — they would extend for 10,000 miles, not just to the gulf, but to both the Atlantic and the Pacific Oceans.

After winning an outright parliamentary majority in 2011, Mr. Harper’s Conservative Party passed an omnibus bill that revoked or weakened 70 environmental laws, including protections for rivers and fisheries. As a result, one proposed pipeline, the Northern Gateway, which crosses a thousand rivers and streams between Alberta and the Pacific, no longer risked violating the law. The changes also eliminated federal environmental review requirements for thousands of proposed development projects.

President Obama’s decision on Keystone XL, expected later this spring, is important not just because it will determine the pipeline’s fate, but because it will give momentum to one side or the other in the larger tar sands battle. Consequently, the Canadian government’s 2013-14 budget allocates nearly $22 million for pro-tar-sands promotional work outside Canada. It has used that money to buy ads and fund lobbyists in Washington and Europe, the latter as part of a continuing campaign against the European Union’s bitumen-discouraging Fuel Quality Directive.

Beginning in 2006, Mr. Harper pledged to promulgate regulations to limit carbon emissions, but eight years later the regulations still have not been issued, and he recently hinted that they might not be introduced for another “couple of years.” Meanwhile, Canada became the only country to withdraw from the Kyoto Protocol. Instead, in 2009 it signed the nonbinding Copenhagen Accord, which calls for Canada to reduce greenhouse gas emissions to 17 percent beneath its 2005 level by 2020. According to the government’s own projections, it won’t even come close to that level.

Climate change’s impact on Canada is already substantial. Across Canada’s western prairie provinces, an area larger than Alaska, mean temperatures have risen several degrees over the last 40 years, causing releases of greenhouse gases from melting permafrost and drying wetlands. The higher temperatures have led to the spread of the mountain pine beetle, which has consumed millions of trees. The trees, in turn, have become fodder for increasingly extensive forest fires, which release still more greenhouse gases. Given that scientists now think the Northern Hemisphere’s boreal forests retain far more carbon than tropical rain forests like the Amazon, these developments are ominous. At least the Harper government has indirectly acknowledged climate change in one way: It has made a show of defending the Northwest Passage, an increasingly ice-free Arctic Ocean link between the Atlantic and Pacific Oceans that winds through Canadian territory.