It’s good that Kennedy Elementary School fourth-graders are getting engaged in the civic process. Last week, students in Lauren Mitchell’s class developed and delivered a presentation to the Lawrence City Commission arguing for a ban on plastic shopping bags.

But while the students should be applauded for their efforts, that doesn’t mean the policy they’re advocating should be adopted. There is much debate surrounding whether the benefits of banning plastic shopping bags outweigh the costs.

No doubt, such bags are an environmental nuisance. Scientists estimate that they take 500 to 1,000 years to break down. Though the plastic is recyclable, most recycling centers don’t accept small plastic shopping bags because they clog sorting machines. As a result, the bags wind up in landfills or, worse, dotting the landscape as litter or in bodies of water. The bags are a threat to wildlife, on land and in the water, which can get tangled in the bags or die from ingesting the plastic. A research study showed that plastic bags accounted for 8.5 percent of all trash found in the Mediterranean Sea.

But there are practical considerations. Foremost, small plastic shopping bags have a much smaller carbon footprint than their replacements, paper grocery bags or reusable canvas or cotton bags. A 2011 United Kingdom Environment Agency study showed that a paper bag would have to be used three times to negate the higher environmental impact of producing paper bags versus producing plastic bags. The canvas bag has the highest carbon footprint and must be used 131 times to negate its impact compared with that of a plastic shopping bag.

And plastic shopping bags also are often reused, sometimes multiple times. And grocery stores have become mindful about making bins available specifically for recycling shopping bags.

The plastic shopping bags are by far the least expensive to produce, and thus are preferred by retail stores. Banning plastic bags or placing an exorbitant tax or fee on their use no doubt would increase the cost of goods in a community.

Ireland was among the first countries to address the plastic bag issue, implementing fees on the use of the bags in 2002. The Irish government reports that bag use has dropped from 350 per person per year in 2002 to 14 per person per year in 2012. And the bags have gone from 5 percent of total litter to 0.14 percent. There are a number of U.S. communities, particularly in California, that have implemented plastic shopping bag bans, though the results are not as defined as Ireland’s example.

City Commission members Lisa Larsen, Jennifer Ananda and Matthew Herbert indicated that a ban or restriction on plastic bags is at least worth a discussion.

“Our task is not just to think about the here and now,” Ananda said, “but to also think about our future generations and how they will be impacted by the decisions that we make today.”

There are no clear cut answers in the shopping bag discussion. But it is a debate worth having, and kudos to the fourth-graders who prompted it.