The Tar(Oil)Sands are the largest proven reserves outside of Saudia Arabia, but mired in sand, this source is the least efficient(only profitable when oil is >$100USD/ barrel), most destructive(2 tonnes of earth moved per barrel and 1.8 billion litres of toxic tailings waste water daily), and dirtiest(single highest source of GHG in Canada- more than entire domestic car fleet) source of oil in the world. This has destroyed huge portions of the Boreal Forest(important carbon sink), killed migrating birds and caribou herds, and toxics leaching from tailings ponds and air pollution has caused a 30% increase in cancers from 1995-2006 in local indigenous communities.

The Alberta tar sands under 4.3 million hectares of Boreal forest, hold 175-300 billion barrels of crude bitumen in the sand, and are between 3.2-4.5 times as carbon intensive to extract as regular oil. 12,000 tones of toxic particulate released into the air and water annually contain Mercury, Arsenic, polycyclic aromatic compounds, heavy metals, and other carcinogenic toxins, causing numerous diseases. Reclamations on the tailings ponds and disrupted ecosystems have been marginal (less than 300 sq km), and the federal government has released documents which question whether rehabilitation is even possible given the levels of toxicity and high costs, for which inadequate funds have been saved at the provincial level, representing a significant environmental and financial risk. Losses of wetlands, habitat, and the carbon sink of the boreal forest (second only to the Amazon in size) are other concerns not adequately understood at this time. The tar sands represent the fastest-growing source of GHG emissions in Canada, with Gov of Canada estimates of 31 million tons of GHG emissions in 2005, scaling up to 92 million tones per year by 2020.