Touted as a convenient and cheap alternative to paper bags, plastic grocery bags gained acceptance in the late 1970s and now meet 80% of retailers' bagging needs. They've saved millions of trees but come with equally bad consequences: more than 500 million are used and discarded each year, millions of which never make it to a landfill and fall as litter. And depending on the plastic used in production, those bags may take several hundred years to decompose. The solution? Recycle, or better yet, skip both paper and plastic and bring a reusable bag of your own.