Paper or plastic? This sounds like an everyday, inconsequential choice, doesn’t it? Many of us have often wondered why plastic bags are bad and so controversial. What harm is really caused by these plastic bags? Aren’t they recyclable? By choosing plastic, aren’t we saving trees? Turns out, there are lots of complex answers to these seemingly simple questions.

How Plastic Bags are Made

One of the first things to note about plastic bags is that they are, like all plastics, made largely of oil. At least 12 million barrels of oil are used each year for the production of plastic grocery bags alone. Oil is a fossil fuel, so harvesting it creates carbon emissions. The transportation of bags from the plant at which they are made to your grocery store also creates huge amounts of pollution.

What Plastic Does to the Environment

Who suffers most from our addiction to plastics? Marine life (aka one of humankind’s main food sources). Have you ever heard of the Great Pacific Garbage patch? This trash vortex, located in the northern Pacific Ocean, is home to hundreds of thousands of square miles of swirling plastic debris. These plastics are often ingested by fish and marine mammals, and are proving to be toxic to these already fragile ecosystems. Additionally, it takes about 1,000 years for plastic bags to break down and decompose–so when these animals die, the plastic is reabsorbed into the system, and the problem continues.

The problem doesn’t only exist in the ocean: Here on land, our landfills and waste facilities are being overrun with plastics. Many people don’t realize that plastic is not infinitely recyclable. Each time you recycle a plastic bottle or bag, the quality of the plastic downgrades. Eventually, these plastics are no longer recyclable and are simply tossed into landfills. Scientists have estimated that about 12.1 percent of municipal waste is composed of plastic–plastic that, as mentioned before, will not break down for more than 1,000 years.

What About Paper?

Paper bags can be a good alternative to plastic bags if you’re in a pinch. Yes, paper is made of trees–but unlike plastic, paper is infinitely recyclable. Paper is also naturally occurring, meaning that it isn’t as hazardous to animals and humans.

Of course, the best choice of all is to bring reusable bags and containers with you to the grocery store. Do this 75 percent of the time and rely on recycled paper bags when necessary, and you’ll be doing the entire world a huge favor.

Combating the Problem

Many of America’s hippest and coolest have begun carrying reusable grocery bags, and many grocers sell them right in the store. Additionally, many cities (and even countries!) have begun outlawing the use of plastic bags, as their consumption puts a serious financial drain on countries’ energy resources (remember–plastic bags are made largely of oil!). Within the U.S, San Francisco, Portland, Long Beach, CA, and parts of North Carolina have passed restrictive ordinances on the distribution of plastic bags.

Abroad, entire cities and countries have gone plastic bag-less. China, Bangladesh and Burma prohibit all use of plastic bags, and Italy, Belgium, Ireland, Switzerland, Holland and Germany all impose extra taxes or fees on their use.