Treaty signals a coordinated opposition to crude oil transport.native Americans head to a rally at the State Capitol in Denver, CO, earlier this month. CREDIT: AP/DAVID ZALUBOWSKIDozens of native tribes from Canada and the United States have joined forces against Alberta’s tar sands crude oil transport with the signing of a treaty Thursday.Calling for a clean and sustainable economy, tribes said any further pipeline or rail development for Canadian tar sands puts indigenous territories and waterways at serious risk to toxic spills. In the Treaty Alliance Against Tar Sands Expansion, tribes also said development “will unquestionably fuel catastrophic climate change.”Tribes signed “this treaty because we needed to, mother earth can’t take any more of this pollution,” Judy Wilson, chief of the Canadian Neskonlith Indian Band, said during the signing ceremony in Vancouver, British Columbia.The treaty comes as oil pipeline development has faced major pressure in North Dakota, where developers of the $3.8 billion Dakota Access pipeline want to build a portion of the line less than a mile from the Standing Rock Sioux Tribe reservation.The pipeline, now under a court injunction, has inspired thousands of tribe members to move into camps near the North Dakota construction site and triggered hundreds of demonstrations across the country. The tribe says cultural and water resources are at risk, while developers say the project is safe and creates jobs.The Dry Weather That’s Hitting The Tar Sands Industry Is ‘A Preview Of The Future,’ Scientist SaysSome 50 tribes, including the Standing Rock Sioux Tribe, have signed onto the treaty, saying they will target proposed development by Kinder Morgan, TransCanada, and Enbridge Inc., Reuters reported. Tribes have for the most part opposed fossil fuel development in the past, particularly when it is close to reservations, but the treaty points to a more coordinated opposition.Alberta’s oil sands are the third-largest proven crude oil reserve in the world, next to Saudi Arabia and Venezuela. Tar sands mining involves removing the top layer of organic matter — trees and plants — before heavy crude oil is filtered from the sand and clay below. Three barrels of water are needed for every barrel of oil extracted from the tar sands, according to Friends of the Earth.Studies have found that air downwind of the largest tar sands producing region in Canada is as dirty as the air found in the world’s most polluted cities.Tar sand development has also helped turn Canada’s energy industry into the largest producer of climate change-causing greenhouse gases in the country, a government report found in 2014.But beyond the staggering effects tar sands mining can have, including significant deforestation and forest degradation, organizations have increasingly questioned crude transport development over concerns of spills.People Who Live Downwind Of Alberta’s Oil And Tar Sands Operations Are Getting Blood CancerJust last summer, Alberta suffered the largest pipeline spill in the province in 35 years, when roughly 1,320,000 gallons, of emulsion — a mixture of bitumen, produced water, and sand — leaked from a Nexen Energy line.“As sovereign Indigenous Nations, we act according to our inherent legal authority and responsibility to protect our respective territories from threats to our lands, waters, air and climate,” the new treaty reads. “Such right is also confirmed by the Constitution of Canada and the United Nations Declaration on the Rights of Indigenous Peoples.”Tribes in Canada and U.S. join forces against tar sands pipeline development was originally published in ThinkProgress on Medium, where people are continuing the conversation by highlighting and responding to this story. Read the responses to this story on Medium.