Sometimes doing nothing can cost a lot of money.

For instance, if Hawaii’s lawmakers just do nothing when it comes to discouraging the use of both paper and plastic shopping bags, they will raise food costs by millions of dollars a year.

How can doing nothing increase food costs?

There’s a bill in the state Legislature that would set a reasonable "single use" fee on both plastic and paper bags. The bill would encourage alternatives to both types of bags. But if lawmakers let the bill die, grocery costs will likely continue to increase in counties that have banned plastic bags.

Here’s why.

Well-intentioned officials in Maui, Kauai and Hawaii counties have banned the use of plastic bags by retail stores. Honolulu City Council members are considering a similar ban. By all accounts, the bans have dramatically reduced the use of plastic bags on Maui and Kauai. And that initially appeared to be a win for consumers and the environment.

But sadly, most shoppers have not chosen reusable alternatives to plastic bags. Retailers on Kauai and Maui report that shoppers now often choose "free" paper bags. And, for retailers, paper bags are up to 10 times costlier than plastic ones. So for one supermarket chain, the extra cost of paper bags is about $600,000 a year or roughly $30,000 per store. Supermarkets on Maui and Kauai have reported similar increases.

Do consumers bear these higher costs? Perhaps not directly, but stores in the competitive grocery business have limited alternatives when it comes to absorbing costs. Cutting jobs or raising prices are two bad choices.

When it comes to bags, what seems to work best is a government fee — as low as five cents per bag on paper and plastic. A modest five-cent fee on paper and plastic reduced the use of single-use bags by 80 percent in Washington, D.C. For Hawaii, that could mean taking 100 million bags or more out of the waste stream every year.

If the Legislature passes a single-use bag fee measure like House Bill 2483, it will reduce consumers’ reliance on single-use bags. Reducing their overall use will help remedy the increased paper costs associated with a plastic bag ban. It will help hold the line on Hawaii food costs, while still allowing shoppers who prefer plastic or paper bags — or who occasionally forget their reusable bags — to use them for a nominal fee.

Economic common sense is not the only reason to support a bag fee. It’s also a matter of protecting our environment. Paper bags take more energy to produce and recycle and generate far more pollution than plastic bags. Banning plastic bags without addressing the negatives of paper makes no sense.

On Oahu, where plastic bags are incinerated at HPOWER to generate electricity, a ban on plastic makes even less sense than it seemed to on the neighbor islands. And now that neighbor island shoppers have shown they’ll use paper bags when plastic bags aren’t available, there’s little reason to believe a plastic bag ban will have its intended effect on Oahu.

It is also important to consider our many visitors, who are less likely to bring reusable bags with them and thus more likely to choose costlier, more polluting paper bags if plastic is banned.

Environmental groups like the Sierra Club have testified at the state Capitol that a bill setting fees for plastic and paper bags is better than a plastic-only bag ban. It’s something on which grocery stores and environmental groups agree.

We need the Legislature to enact a state bag fee law before the session ends on May 3. Doing nothing is a costly option.