With its recent flurry of green initiatives, Wal-Mart has won the embrace of several prominent environmental groups. "If they do even half what they say they want to do, it will make a huge difference for the planet," said Ashok Gupta of the Natural Resources Defense Council. Environmental Defense, meanwhile, has deemed Wal-Mart's actions momentous enough to warrant opening an office near the retailer's headquarters in Bentonville, Ark. "If [we] can nudge Wal-Mart in the right direction on the environment, we can have a huge impact," said the organization's executive vice president, David Yarnold. Wal-Mart's eco-commitments are not without substance. …