We owe it to future generations to bag plastic shopping bag usage in Colorado's largest city. Los Angeles did it in May 2012. San Francisco did it in 2007. Many European cities did earlier than that. Heck, Aspen and Carbondale did it in early 2012. But Denver grocery stores and pharmacies still package customers' products in plastic bags - even though more than 1 trillion bags are used worldwide each year, and fewer than 5 percent of those are recycled. For those that aren't recycled: They'll take up to 1,000 years to degrade in our parks, landfills and oceans.