"Will it be paper or plastic?" Each year consumers in the US are asked to make this choice when at the checkout stand. Many grocery stores offer these two choices; however, both paper and plastic have significant environmental impacts.
Plastic bags are less expensive to make than paper but, it takes about 12 million barrels of oil per year to make plastic bags for US consumers, and about 330 million barrels of oil to make all forms of plastic in the US.
Plastics decompose slowly in direct sunlight, but are extremely dangerous if not recycled. It is estimated that 100,000 animals die annually due to strangulation.
Paper bags are more expensive to manufacture than plastic bags, and take up more room in landfills. Paper will not break down efficiently in a landfill.
Both paper and plastic increase carbon footpring when disposed of, both create significant carbon gases during breakdown in landfills.
While cloth bags are more expensive initially, they are capable of long-term usage and save trees and petrolium resources.
Excellent paper vs plastic comparison graphic from Washington Post.
Oberlin College Resource Conservation Team, recycling facts
Educational presentation, Paper or Plastic
Using cloth bags save natural resources and help the environment.
Reusable shopping bags in Nashville.
Going Green in Tennessee