NEW YORK (Fortune) -- If your mailbox looks anything like mine during the weeks before Christmas, it is overflowing with catalogs.

Retailers mailed out about 19 billion catalogs last year, according to the Direct Marketing Association. Most of the paper in those catalogs - as much as 95% - comes from trees, and not recycled sources. And most catalogs quickly wind up as trash. What a waste.

Happily, that's beginning to change, thanks in part to a pesky and persistent advocacy group called ForestEthics which has persuaded a number of Fortune 500 companies to buy paper in ways that will preserve valuable forests.

In the last month or so, three big retailers that mail out hundreds of millions of catalogs - Dell, Williams-Sonoma and the Victoria's Secret unit of Limited Brands- have pledged either to buy more recycled paper or to increase their purchases of paper that comes from trees that are harvested in sustainable ways.

Others face pressure to follow. "We're looking at L.L. Bean, Sears, Lands End, J.C. Penney, J. Crew - they're at the top of our list," says Todd Paglia, the executive director of ForestEthics. "This is an industry that is ripe for change."

San Francisco-based ForestEthics is small, when compared with better-known green groups like the Nature Conservancy or Sierra Club. It has just 35 staff people and an annual budget of $2.6 million.

But companies that ignore ForestEthics do so at their peril. The group has been cajoling and threatening big players in the catalog industry, and last year it unleashed an unfriendly ad campaign against Victoria's Secret. Its "Victoria's Dirty Secret" campaign used scantily-clad models brandishing chain saws to make the point that the 390 million or so catalogs sent out each year by Victoria's Secret require cutting down a lot of trees.

But while ForestEthics and Victoria's Secret battled in public, they negotiated in private. The 39-year-old Paglia met several times with Tom Katzenmeyer, a Limited Brands senior vice president, and eventually he was invited to make his case before the company's directors and its chief executive, Leslie Wexner.

Last week, Victoria's Secret and ForestEthics announced that the company's catalogs will in the future use either 10 percent recycled paper or 10 percent paper from sources certified as sustainable by the Forest Stewardship Council, an independent group. (Sustainable means that logging practices will preserve forests.)

"We're hoping the logging, pulp and paper industry will rise to the occasion," said Katzenmeyer of Limited Brands, according to the Reuters news agency.

The company also said it would not buy paper from pulp mills that log endangered portions of Canada's vast Boreal forest, which stretches across northern Alberta and British Columbia. (ForestEthics has accused some mills of disrupting caribou habitats, a charge strongly denied by the Canadian paper industry.) Victoria's Secret also said it will donate $1 million towards research on endangered forests and report publicly on its paper-buying practices.

"This is a level of transparency you don't see a lot in corporate America," Paglia said, and he wasn't talking about the lingerie on the Victoria's Secret models.

Dell and Williams Sonoma haven't gotten as much attention for improving their paper-buying practices despite the fact that they're going a lot further. Neither was the target of a campaign, but Forest Ethics consulted informally with both firms.

Dell said last month that its catalogs and marketing materials now use an average of 50 percent recycled content, a target it had earlier promised to hit by 2009. Dell has also promised to buy 25 percent of its paper from sources certified by the Forest Stewardship Council. Its policy can be found here.

Williams-Sonoma said that it will begin sourcing about 95% of its catalog paper from FSC-certified sources. Forest Ethics initially criticized the company, but they soon became allies. "There was a little bit of uneasiness when we first met," said Pat Connolly, the firm's chief marketing officer, "but they grew to understand that we had a lot of the same goals that they do." Williams-Sonoma, for example, has used recycled pellets in its packaging materials for years.

All of this is good news for the Forest Stewardship Council, which is competing with an industry-backed group called the Sustainable Forestry Initiative to become the most credible global standard for good environmental practices in the paper industry.

Of course, the best way to save more trees would be to keep more unwanted mail out of our mailboxes, much as we have been able to cut down on telephone sales pitches by signing up with a "do-not-call" registry.

Several groups, including ForestEthics and the Center for a New American Dream, want Congress to make it easier for people to keep unwanted mail out of their homes with a "do not mail" list. Right now, you can opt out of bulk mail through a website run by the Direct Marketing Association but it's not easy and it will cost you $1. You can also call retailers, and they will take your name off their lists.