July 2, 2008 - Wal-Mart has pledged to buy more of its produce from local farmers in a bid to cut shipping costs and support local economies.

The retail giant says its partnerships with local farmers have increased 50% over the past two years. Wal-Mart expects to source about $400 million in locally grown produce from U.S. farmers this year.

Currently, about a fifth of the produce available in Wal-Mart stores is grown in the state where it will be sold, according to Wal-Mart.

“Food miles” refers to the distance food must travel from farm to fork. The concept of food miles is more popular in the U.K., where Wal-Mart-owned supermarket ASDA has had a local sourcing program for several years, and supermarket chain Tesco has begun labeling some products according to carbon footprint "from seed to store."

But the metric is now getting greater play in the U.S. as well. In June, for example, restaurant chain Chipotle pledged to source more local ingredients, citing the benefit to health and environment.

With these new initiatives, however, have come challenges from critics who charge that food miles don't tell the whole story. Click here for SLM sourcing expert Phil Berry's take on why food miles still matter.