The question before the Legislature is, paper or plastic? And when it comes to the health of our planet, it’s not as simple as you think.

The Environment and Natural Resources Committee this week held a hearing on L.D. 1532. Sponsored by Rep. Holly Stover, D-Boothbay, the bill would ban single-use plastic bags at retailers across the state. It would also add at least a 5-cent fee for paper bags. A similar bill fell just short last year.

California, Hawaii and New York have passed plastic bag bans. Across the country, more than 200 cities and counties have enacted bans or placed fees on plastic bags, including 21 Maine municipalities. (A ban passed in Waterville last year, but the outcome is being disputed.)

Why? Plastic bags are a waste. Americans use about 100 billion of them a year, and though they are recyclable if returned to a retailer, most end up as trash. They fill up landfills, contaminate streams of recyclables and bust recycling machines. They float in our rivers, lakes and oceans. They litter roadsides, clog drains and kill wildlife.

In total, single-use bags make up 12 percent of total plastic waste in the U.S., and getting rid of them would be a boon to the environments and habitats they now soil.

But something would have to take their place — and that’s where it gets tricky.

One study of California’s ban found that it absolutely cut back on the use of plastic bags — the cities analyzed contributed 40 million fewer pounds of plastic to the waste stream.

But the sale of garbage bags — particularly smaller ones similar to grocery bags — increased too, as people looked for replacements to carry their lunch or pick up after their pets. Those bags are thicker than the ones given out in stores, so they add more per bag to the waste stream.

Use of paper bags took off as well, and paper waste went up by 80 million pounds.

If the planet’s health is the concern, then it makes sense to look at the carbon footprint of each bag as well. The answer may surprise you.

First off, reusable cotton tote bags, which take a lot of energy to manufacture, score out the worst; one study in the United Kingdom found you’d have to use a cotton bag 131 times to have it beat out a single-use plastic bag when it comes to carbon footprint.

You’d have to make at least four to 11 trips to the store with a reusable plastic bag and at least three trips with a paper bag before they were better on emissions than a single-use bag, studies have argued.

So while a ban would take single-use plastic bags out of the equation — off our roadsides, and out of our rivers and wildlife — it would not necessarily reduce overall waste or carbon emissions.

The economist behind the UK study favors a fee on plastic bags, which she says is enough to encourage the use of reusable bags while allowing others to still use the single-use bags where it makes sense.

Lawmakers should keep that in mind as they debate a ban. Our reliance on single-use plastic is a waste and a travesty, and a ban would get a significant amount of it out of the waste stream.

That would be a victory for the environment. But unless people replace those single-use bags with reusable ones — and actually reuse them — it would be an incomplete one.