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We’ve all heard of the plastic menace. Plastic bags litter streets, trees, and streams. They suffocate wildlife. They can take over 1,000 years to decompose. And we’re only consuming and throwing away more of them every year.

They also have a knack for getting into the world’s oceans. Plastic bags and cigarettes account for more than 80 percent of marine litter, according to a recent landmark study by the U.N. Environment Programme, or UNEP. They are eaten by all kinds of fish and kill an estimated 1 million seabirds a year. The Great Pacific Garbage Patch, an island of litter twice the size of Texas floating in the Pacific Ocean, is largely made up of plastic. UNEP says cutting bags off at the source is much cheaper than removing them later.

Enter the bag tax. A bag tax works by charging shoppers a fee—typically between 5 and 30 cents—for every bag they get in a store. This fee drives consumers to buy reusable bags and change their habits. It also causes high-quality reusable bags to emerge and diffuse because it’s a market solution. The resulting revenue can be used to raise awareness, to pay for environmental clean up, or to subsidize reusable bags.

Paper bags, often touted as a green alternative, aren’t any better for the environment—they drive deforestation, take four times more energy to manufacture, and 10 times more energy to recycle. This means less litter but much more global warming, so an effective tax should therefore cover both kinds of bags.

Bag taxes have worked in other countries. Ireland’s famous PlasTax, passed in 2002, cut an astounding 90 percent of bag use within weeks. It has not only changed consumer habits, but also social norms—carrying a plastic bag is seen as the moral equivalent of smoking on a plane.

In China, where plastic bags are referred to as “white pollution,” the parliament outright banned them in 2008. The measure cut plastic bag usage by 66 percent in its first year, saving 40 billion bags and 1.6 million tons of petroleum despite some initial problems with compliance.

The idea has taken off worldwide. Taxes or bans have been implemented in Australia, Russia, Italy, Germany, Switzerland, the Netherlands, Hong Kong, and South Africa. Thin plastic bags have even been banned in some of the world’s poorest countries, including Eritrea, Rwanda, Somalia, Tanzania, Kenya, and Uganda.

Detractors argue that the added fees hurt the poor. Smart bag taxes address this problem by using the revenue to buy reusable bags for low-income families. Critics also point out that people can already recycle plastic bag in many supermarkets. The problem is that consumers don’t—at least not nearly enough to solve the problem. According to the Environmental Protection Agency, only 10 percent to 15 percent of paper bags and 1 to 3 percent of plastic bags are recycled in the United States.

Cities in the United States have been leading the charge against the plastic nuisance. San Francisco became the first American city to ban the bags in 2007. Los Angeles has passed a tax as well that goes into effect next year. And just last month, Washington, D.C.’s city council approved a five-cent fee on both paper and plastic bags. It will go into effect following a public awareness campaign and distribution of reusable bags to low-income residents.

But the nationwide push against plastic bags has been turbulent. Portland, Oregon’s Mayor Sam Adams backed off his own bag tax proposal earlier this year. In May, Philadelphia’s City Council killed another promising initiative under intense industry pressure. On August 18, Seattle will vote on a bag fee modeled after Ireland’s successful PlasTax. The political battle, however, has been intense: Plastic bag industry lobbyists have poured over $750,000 into a campaign to kill the measure, and voters are divided.

At the state level, bag tax bills have been proposed in Connecticut, Maryland, Massachusetts, Virginia, and Texas, but none have passed yet.

There has even been some movement in Congress. Rep. James Moran (D-VA) introduced the Plastic Bag Reduction Act of 2009 in June. The bill would phase in a nationwide five-cent fee on both paper and plastic bags starting in January of 2010, increasing to a 25-cent fee by 2015.

The case for a national bag tax is clear. Plastic bags are a huge and growing problem. They’re not free, either, since retailers pass on the costs to consumers. In comparison, good reusable bags pay for themselves in no time. Bag taxes have been proven effective, and many other countries have passed them. It’s time that we do, too.

Read more articles from the "It’s Easy Being Green" series