Wal-Mart Stores Inc., is putting the onus on its suppliers, including fresh produce shippers, as part of a goal to cut 20 million metric tons of greenhouse gas emissions from the retailer’s global supply chain over the next five years.

Fresh fruit and vegetable growers are among hundreds of Wal-Mart suppliers, and what steps they may take as part of the new effort isn’t yet clear. Wal-Mart has already been buying more fresh produce from local growers in recent years, lowering transportation costs.

Such direct-from-farm purchasing “not only reduces energy use and emissions, but also delivers a superior product to the consumer,” Matt Kistler, Wal-Mart’s senior vice president of sustainability, said during a media conference call Feb. 25.

“It’s fresher, and we experience less waste in our stores.”

For the fresh produce industry, Wal-Mart’s emissions-cutting plan may compel the use of more energy-efficient refrigeration or shipping, observers said.

Fruit and vegetable growers have already been on a path to sustainability, said Kathy Means, vice president of government relations and public affairs for the Newark, Del.-based Produce Marketing Association.

Wal-Mart is a member of the association.

Wal-Mart’s effort “is not out of line with what the produce industry is already doing,” Means said.

Fresh produce “tends to have a lower carbon footprint than a lot of others in the food industry. The products themselves are part of this sustainability.”

The world’s biggest retailer is partnering with the Environmental Defense Fund to work with Wal-Mart suppliers on identifying ways to reduce pollution and energy costs, Wal-Mart and the EDF announced Feb. 25.

Wal-Mart’s global supply chain carbon footprint is “many times” larger than its operational footprint and “represents a more impactful opportunity to reduce emissions,” according to a statement from the Bentonville, Ark.-based retailer.

“We know that we have an opportunity to do more and the capacity to do more,” Wal-Mart chief executive officer Mike Duke said in the statement.

The 20-million-metric-ton reduction target would be the equivalent of taking 3.8 million cars off the road for a year, Wal-Mart said.

Emission-reducing efforts will focus on product categories with the highest carbon footprint. The company did not list specific categories. Wal-Mart wants suppliers to curb emissions from raw materials sourcing, manufacturing, transportation, customer use or “end-of-life” disposal.

Fred Krupp, president of the New York-based Environmental Defense Fund, said in the release that Wal-Mart’s program will have far-reaching effects around the globe.

Wal-Mart announces ambitious sustainability plan