S ome activists, being human, seek an end to public debate the instant they convince a government body to adopt their pet regulation. We won, the thinking goes, so move on.

But scientists, economists and others keep working, and what they find sometimes casts those pet regulations in a less than flattering light.

What’s a poor elected official — in this case a Bend city councilor — to do?

In December, councilors voted to ban single-use plastic shopping bags, beginning in July. Doing so, they reasoned, would teach consumers about waste reduction and sustainability, cut down on littering, protect marine life from plastic pollution and reduce clogs in recycling equipment.

If these bags were considered environmentally beneficial, environmentalists surely would point to other solutions. They’d urge people to quit littering and sticking their plastic bags in the recycling bin. But single-use bags are bad, period. Everybody knows that.

Or do we?

One month after City Council banned bags, the Journal of Environmental Economics and Management published the results of a study that quantifies one unintended consequence of similar bag bans instituted in California. When shoppers were no longer able to reuse their supposedly single-use bags as trash bag liners, dog-poop bags and so on, economist Rebecca Taylor discovered, they ended up buying more trash bags. A lot more trash bags.

Taylor’s study, “Bag leakage: The effect of disposable carryout bag regulations on unregulated bags,” reports that sales of small, medium and tall trash bags increased by 120%, 64% and 6%, respectively, in the wake of bans on single-use bags. These increases endured for years.

One argument for banning single-use bags is that doing so reduces plastic consumption and, therefore, fosters sustainability. And, sure enough, Taylor found, California’s bag bans reduced plastic consumption by about 40 million pounds per year. However, consumers who turned around and bought thicker trash bags to line their cans, pick up their dog poop or whatever contributed 12 million pounds of plastic to the waste stream that they wouldn’t have otherwise. Almost 30% of the “saved” plastic consumption wasn’t saved at all.

A “substantial proportion of carryout bags,” Taylor writes, “were already reused in a way that avoided the manufacture and purchase of another plastic bag.”

Given the environmental effects of plastic production, this isn’t particularly great news. Still, the bag bans forced a lot of people to use reusable bags or paper bags. And these are better than throw-away plastic bags, right?

Not necessarily. Other research, Taylor notes, complicates such claims. You’d have to use a cotton carryout bag 131 times to equal the carbon footprint of a carryout bag that isn’t reused. You’d have to use it 327 times if all carryout bags are reused. A paper shopping bag, meanwhile, would have to be used four times. When’s the last time you did that?

“Life-cycle assessments of carryout bags,” Taylor writes, “have consistently found that plastic carryout bags take significantly less energy and water to produce, require less energy to transport, and emit fewer greenhouses gases in their production than paper and other types of reusable bags.”

There are other measures of a bag’s environmental impact than these, of course. Single-use plastic bags are easily carried by wind, for instance, and can end up in the ocean more easily than paper bags and reusable bags. But these problems, like recycling-machine clogs, are largely a consequence of improper disposal. And the odds that a single-use plastic bag distributed in Bend will end up in the ocean are vanishingly small.

More and more, Bend’s ban on single-use bags seems to be little more than a capitulation to people determined to join a popular movement that vastly oversells its environmental benefits. That’s a pretty thin justification for micromanaging both businesses and consumers.

What, then, could the City Council have done to make shopping a more environmentally friendly exercise?

One possibility, notes Taylor, is to “incentivize the production and sale of inexpensive, thin grocery bags that are specifically designed and marketed to be used as trash bags after their use as carry-out bags.” These would have to be thin enough so that their carbon footprint “would not exceed thin plastic grocery bags.”

What this looks like in practice is a modest (say, 5 cents) fee on single-use bags, combined with a campaign to educate people about secondary uses. More consumers presumably would understand that by using a single-use bag at the store, they can avoid the need to buy additional trash bags.

That isn’t what Bend City Council has done. Nothing, though, prevents environmentally conscious consumers from taking this route themselves. They can accomplish this by buying their own single-use bags (they’re cheap), reusing them, then seeing that they end up in the dump.

— Erik Lukens is editor of The Bulletin.