Hey Mr, Green, Please tell me how to get off catalog mailing lists. --Richard in Ann Arbor, Michigan

For most people, junk mail is a waste of time--and trees. A staggering 17 billion catalogs, requiring more than 3.5 million tons of paper, are sent to Americans each year. Making all that pulp takes about 60 million trees, some of them from endangered forests.

If you're already on a company's mailing list, contact it directly (by going to its Web site or calling customer service) to keep its fiber-intensive material out of your mailbox. To prevent new companies from harassing you, get on the "do not mail" list by writing to Mail Preference Service, Direct Marketing Association, P.O. Box 643, Carmel, NY 10512 or registering online at dmaconsumers.org/cgi/offmailinglist. Unfortunately, the system doesn't distinguish between greedy corporations and noble nonprofits, so this action may cut you off from worthy charitable appeals.

But what about us losers who actually like getting junk mail? (It's so inspiring to see how those brave Victoria's Secret models can manage to smile even when contorted into postures that manifest severe sacroiliac disorders.) We have a serious obligation to prod the catalog industry to use more recycled paper and sustainably harvested timber, or the world's forests will be as empty as our lives. Find out about ForestEthics' campaign to do just that at victoriasdirtysecret.net.

Hey Mr. Green, Why hasn't hemp replaced trees for use in paper? --Robert in Williamstown, Massachusetts

First, a disclosure: I've got a serious pro-hemp bias 'cuz hemp's in my blood. And not from inhaling. During World War II, my dad harvested hemp seed for Midwestern farmers who provided the fiber for ropes that helped strangle Axis fascists. It's crazy that what was patriotic then is criminal now. (You've surely heard how hemp was banned in 1937 due to antimarijuana hysteria, legalized during the war, and banned again afterward.)

Farmers ought to demand legalization--which might end up being more useful than subsidies for corn, soybeans, sugar, and wheat--and environmentalists should join the chorus. On less than 5 percent of our arable land, we could produce enough hemp fiber to replace all the pulp now produced in the United States. And that's not even getting into the prospects of hemp as a source of fiber for cloth. Granted, hemp is no immediate panacea for deforestation; there are loads of technical, agronomic, and economic problems that would have to be solved first. Paper mills would have to be retooled and new processing techniques developed. Since hemp is an annual crop, it would require a lot more labor and capital to till the land, plant the hemp, and cultivate it than to wait for trees to grow. And since hemp would be harvested at the same time each year, we'd need to find ways to harvest, dry, and store it, so it wouldn't all rot before it could be processed into paper.

But as long as it's illegal to grow the stuff, there's little incentive to develop technology for processing it, any more than there would be to design internal-combustion engines if burning oil were prohibited. Fortunately, there's a bill in Congress to legalize hemp cultivation, H.R. 3037, sponsored by Representatives Sam Farr (D-Calif.), Raul Grijalva (D-Ariz.), Jim McDermott (D-Wash.), George Miller (D-Calif.), and Ron Paul (R-Tex.). Tell your representative to get with the program and give hemp a chance.

Read more advice from Mr. Green, including his Web-only mailbag, and submit your own environmental questions at sierraclub.org/mrgreen.

Mr. Green illustration by Melinda Beck; used with permission.