First, people wanted to save trees. Then, they wanted to save the oceans.

In between are retailers, trying to keep up with how customers want to carry their purchases, how best to react to environmental concerns, how best to juggle rules and regulations, and how to make it all work with their bottom line.

"The grocery business finds itself in an interesting predicament," said Brandon Scholz, president and chief executive of the Wisconsin Grocers Association. "If everybody used a recycled or reusable bag? Fantastic. It goes to our costs.

"But if you ban plastic bags and you want to drive people to use paper, you're going to drive costs to the retailer up," he added. "And who's going to pay for it? It's not going to be the retailer."

These are busy times in the bag world. Madison's mandatory plastic bag recycling law, which took effect in December, was one of many recent moves made by communities, organizations and retailers to respond to environmental concerns and consumer trends. For example:

• On Jan. 1, Washington, D.C., instituted a 5-cent tax on paper or plastic bags at stores that sell food or alcohol, with the proceeds going to pay for cleaning up the Anacostia River.

• On Jan. 2, three Walmart stores in Northern California stopped offering free bags at checkout in an experimental policy begun by the company. Shoppers must bring their own bags or pay at least 15 cents to buy a reusable polypropylene fabric bag.

• On Jan. 6, the Brownsville (Texas) City Commission approved a ban on plastic shopping bags beginning in 2011. San Francisco became the first U.S. city to ban the bags in 2007.

• Last year, the home improvement store chain Menards switched its popular bag sale from 15 percent off everything that can fit into a paper bag to everything that can fit into a reusable bag that can be brought in or purchased for 98 cents. The sale ran again in early January.

• The national Best Bagger Championship has contestants packing reusable bags for the first time at its contest in Las Vegas on Feb 11.

The bag debate has gone on for decades. First, there was concern about trees felled for grocery sack production, which led to stores switching to or adding the option of plastic bags in the 1980s. Customers then became concerned about plastic bag littering and the dangers the bags posed to marine life. There also were concerns about putting them in landfills.

Sherrie Gruder, a sustainability specialist at UW Extension, said that while most of the plastic bags will never break down in the environment, paper can take decades to decompose in a landfill because it isn't exposed to light, moisture or oxygen.

"Anything that goes to a landfill is a waste of resources," she said. "The idea is to use less in the first place."

Advocates for paper or plastic cite environmental advantages and disadvantages with each.

"I don't think grocery stores are the bad guys," said Mitch Eveland, owner of Capitol Centre Foods at 111 N. Broom St. "If your store makes an effort to accept those bags and gives you an incentive not to use those bags, I think the customer really appreciates that."

Eveland's store gives a 10-cent discount for bags brought into the store for grocery use.

Even before the plastic bag recycling law went into effect in Madison, many grocery stores were drop-off points for plastic bags. In addition, many grocers have offered discounts for bringing in reusable bags.

"The consumers have really warmed up to bringing bags in, both paper and plastic and the reusable ones," said Tim Metcalfe, owner of Metcalfe's Market at Hilldale Shopping Center.

The Roundy's Supermarkets chain, which in the Madison area includes Pick 'n Save and Copps stores, offers 5-cent discounts for reusable bags, and stores have drop-off sites for plastic bags.

With some stores, there's an option to keep the discount or donate it. At Miller and Sons stores in Verona and Mount Horeb, customers get 10 cents for each bag they bring in to use for groceries, and Carl Miller, the stores' owner, estimates about $800 to $1,000 is donated monthly to a food pantry in Verona. In Mount Horeb, the program to donate to a local garden club began before Miller owned the store, and $2,759.70 was donated last year.

Metcalfe's gives its customers 10 cents back for each bag they bring in, and the store is in the process of offering an option to donate it to a charity that will change monthly.

Last year, Metcalfe said, his two stores -- at Hilldale and in Wauwatosa -- gave out $48,000 in bag refunds. He said he started the discount about 10 years ago, and few customers did it at first.

"Now, it's turned out to be a fairly major line in our (profit and loss)," he said. "We save the money by not having to buy another bag and we don't put another bag in the landfill."

Eveland and Miller said they, too, have saved money in bag purchasing, but those savings might not last, Scholz said, if grocers are forced to choose paper over plastic. Grocers pay about 1 cent for a plastic bag and 6 cents for a paper one.

Whole Foods stopped offering plastic bags at cash registers nationwide in 2008. The Willy Street Co-op has never offered them.

Inexpensive reusable bags are catching on beyond grocery stores; retailers of all kinds are offering polypropylene sacks that often sell for about $1. Shoppers like them because they stand like a paper sack and are easier to bag. They're now common at national retail stores such as Menards, Walmart, Target and Kohl's.

"Even the Ace Hardware next door to us has them," Miller said.

Scholz opposed Madison's plastic bag law, mostly because he thought city resources would have been better used to encourage recycling rather than to require it.

"We're not against it," he said. "We just said, ‘Look, we already have the bins. Why don't you spend the money educating consumers to bring the bags in?' People don't go to the city sites to drop them off, they go to the grocery stores."

Scholz said his association's Green Grocer certification program was a direct result of the movement to ban plastic bags. The voluntary program certifies stores that take at least 50 of 71 steps toward energy efficiency and conservation. Recycling plastic bags is mandatory.

"That came out of wondering what we could do to prove to the Legislature or the government that we don't need mandates to reduce our energy consumption, but as an industry, we can take steps to do it on our own," he said.

Consumers have been educated about recycling, and the pros and cons of paper or plastic, and there's no shortage of recyclable bags for them to use. But there is one lesson customers have yet to learn: "All those bags are in the cars, they need to remember to bring them in," Miller said. "Ninety percent of the customers you carry out for, their bags are in their car."