How wood is harvested, and where, is at the center of the relationship Home Depot and the environment.

And one of the key aspects of the company’s approach to the environment is its wood purchasing policy.

The Atlanta-based retailer first instituted the policy in 1999 with an eye toward protecting endangered forests and shoring up the timber supply for future generations. In essence, the policy comes down to giving purchasing preference to wood that comes from forests that are managed in a responsible way, and cutting out the use of wood from areas with endangered forests.

For example, while the company has never purchased large amounts of wood from areas with rainforests, trees around the Brazilian Amazon Basin now contribute less than .15 percent of the wood Home Depot purchases.

In order to be sure that the company was buying timber responsibly, company officials decided they needed to trace the origin of every item the chain sells. And Home Depot can now say it knows even where the wood on a broom handle comes from. More than 94 percent of the wood Home Depot sells is grown in North America. A little over two percent comes from South America.

The retailer promotes the use of “certified” wood. The term indicates wood that has been harvested sustainably under strict guidelines and monitored by a third-party auditor. Consumers can trace the journey of all wood that has the FSC label from its origin through manufacturing and distribution to the store shelf.

One third-party monitor of certified wood is the Forest Stewardship Council, which is based in Germany. The FSC has developed a set of ten forest management principles that include maintaining the ecological functions and the integrity of forests, and observing the rights of indigenous people to manage their own lands.

Home Depot says it sells more FSC-certified wood than any other retailer in the U.S. It has also moved aggressively to encourage its vendors to buy certified wood. From 2006 to 2007, the chain sold more than 400 million pieces of FSC-certified wood products.

The company has introduced a line of building supply materials, including shelving, that are manufactured from wheat straw. In many cases, the wheat straw is a substitute for tropical hardwoods that are considered endangered.

This is one of many product shifts the company has undertaken to promote sustainable forestry practices. Home Depot has substituted more sustainable wood in many of the more common products it stocks, including blinds, doors and cabinetry.

The embrace of certified wood has led Home Depot to limit its purchases from some countries in favor of nations where forests are managed more responsibly. The company, for example, shifted additional wood purchases out of Malaysia, Russia and Papua New Guinea in 2007 and 2008.

The company has pledged not to buy uncertified wood from a group of forestral eco-regions that the World Wildlife Fund identified in 2001 as the most vulnerable. Those eco zones include Madagascar’s mangroves, Cameroon’s Highland forests and Southern Pacific Island forests. And unless a supplier can provide an export permit, the chain won’t purchase wood products that are made from 40 species of trees that the World Conservation Monitoring Centre has deemed potentially endangered species.

Home Depot has taken a number of steps aimed at limiting the purchase of specific types of wood that are known to be endangered.

• For example, wood from ramin trees, which are found in Indonesian and Malaysian swamps, has often been used in small rods called dowels that are sometimes employed to align two pieces of wood or material. But ramin is an endangered species so Home Depot has substituted FSC-certified eucalyptus dowels.

• The chain has also reduced the use of lauan wood in doors. Lauan wood is a term for tropical plywood that comes from the Philippines, Indonesia and other places. In Indonesia, for example, Home Depot has reduced its purchases of lauan wood by more than 70 percent. The lauan wood vendors it continues to work with are seeking certification and have agreed to third-party audits.

• Home Depot has also begun to source 90 percent of the cedar it buys from second- and third-growth forests in the U.S.

For more information on Home Depot and the environment, check out the environmental initiatives section of the company’s website.