Tar sands are massively CO2 intensive, as well as hugely destructive of land. Take a look at satellite imagery of extraction areas - they literally tear the surface of the earth off. Watercourses are polluted with all kinds of horrible poisons as a result. One has to be wilfully ignorant or cynical to ignore the fact that we really shouldn't be exploiting this energy resource at all if we want to avoid cooking the planet, in favour of praising a method that facilitates even greater destruction. Where does it end?! :|

Don't forget the tailings ponds that are constructed to park the waste and residue chemicals from extraction and processing. They are simply left there until time and eventual facilities decay allow them to leak into nearby waterways.