Meanwhile, green thinktank Sightline has an interesting post about the environmental impact of paper vs. plastic. Their number crunching revealed that "assuming a grocery bag holds one day's worth of food for a family of four, the choice about what to put in the bag is about 186 times as important as the bag itself." Meaning, the food you eat has a much bigger impact than the bag you use.
That's a good point to keep in perspective as Portland gets into debating the nitty gritty of banning plastic bags from grocery stores. The Sightline report also notes that from an energy standpoint, using a canvas bag is 14 times better than plastic (without factoring in the littering, landfill and oil issues) while they're 39 times better than paper.