Won't sell any catch from endangered areas.

Recently, I was in Bentonville, Ark., working with the world's biggest retailer to develop its long-term commitment to buy 100% of its fresh and frozen, wild-caught fish in its American stores from fisheries that are certified to be "sustainable." The company made a similar commitment regarding the purchase of all farmed salmon and farmed shrimp only from "sustainable" aquaculture operations.

This is big news in the fisheries world because it is the first time any retailer has committed to buying 100% from fisheries that are certified to be sustainable. And, Wal-Mart, this first retailer, is the biggest.

What are we talking about when we speak of "sustainability" and a "sustainable fishery"? And, what is the significance of Wal-Mart's commitment?

Sustainability is a concept that ties economic activity to environmental responsibility, producing what is known as the "double bottom line" of profit plus environmental stewardship. A sustainable fishery is one that is certified by independent specialists to meet the Marine Stewardship Council's standards, including avoiding overfishing the resource and avoiding harm to the marine habitat from fishing practices. A sustainable fishery respects and protects the resource and the habitat of the fish.

You've probably seen news items about the current problems in the world's oceans, including the decline of fisheries. Today, roughly 70% of ocean fisheries are exploited to the max or over-exploited. By buying only from the "good" fisheries, Wal-Mart is using the power of the market to help ensure that the good guys are rewarded and the bad guys are avoided.

This also sends a message to shoppers that the company is seeking to be a responsible corporate citizen. In addition, Wal-Mart has a stake in keeping its sources of supply in a productive condition over the long-term.

The impacts of this commitment to sustainability by the world's largest company cannot be overestimated. This is a business that accounts for 2% of the gross domestic product of the U.S. economy, that has 1.5 million employees and that, if it were a nation, would be the 19th largest economy in the world, ahead of Sweden, Saudi Arabia, Greece, Argentina and a hundred other nations. It buys a lot of fish.

The company casts a huge shadow. Its example already is having a ripple effect in the commercial world, as the globe's third largest food retailer later committed to buying fish from sustainable fisheries.

Leadership in the field of environmental sustainability is relatively new for Wal-Mart, but it is developing the knack quickly, as revealed by a visit to its Web site.

The company's sustainability goals are listed as: "to be supplied 100% by renewable energy, to create zero waste and to sell products that sustain our resources and our environment." Wal-Mart has been the subject of some controversy in the past, but you've got to applaud a company with such bold new goals.

The company's CEO, Lee Scott, has added policy vision to the company's legendary focus on cutting product costs. Scott asked his managers what the company should be thinking about today that will be expected of all companies 10 years down the road.

He told me one of the answers he got was "sustainability". This new fish deal is evidence Wal-Mart is acting on this theme, and other businesses should look and listen carefully.