The local-and-sustainable food movement has spread to the nation’s largest retailer.

Wal-Mart Stores announced a program on Thursday that focuses on sustainable agriculture among its suppliers as it tries to reduce its overall environmental impact.

The program is intended to put more locally grown food in Wal-Mart stores in the United States, invest in training and infrastructure for small and medium-size farmers, particularly in emerging markets, and begin to measure how efficiently large suppliers grow and get their produce into stores.

Advocates of environmentally sustainable farming said the announcement was significant because of Wal-Mart’s size and because it would give small farmers a chance at Wal-Mart’s business, but they questioned how “local” a $405 billion company with two million employees  more than the populations of Alaska, Wyoming and Vermont combined  could be.

Given that Wal-Mart is the world’s largest grocer, with one of the biggest food supply chains, any change it made would have wide implications. Wal-Mart’s decision five years ago to set sustainability goals that, among other things, increased its reliance on renewable energy and reduced packaging waste among its suppliers sent broad ripples through product manufacturers. Large companies like Procter & Gamble redesigned packages that are now carried by other retailers, while Wal-Mart’s measurements of the environmental efficiency of its suppliers helped define how they needed to change.