A recent New York Times article about the Environmental Defense Fund’s efforts to help Wal-Mart “cut waste” painted an incomplete picture of the group’s relationship with the retail giant, offering an instructive lesson in “green business” coverage in the process.

The article, which ran on the front of the paper’s business section on April 13, described Wal-Mart’s “mixed degree of progress” toward achieving a variety of goals—from recycling, to energy use, to fuel efficiency—that it set for itself in 2005. The “environmental push has helped transform public opinion of the company, easing the way for it to open stores in urban areas like Chicago and Los Angeles,” the Times’s Stephanie Clifford reported, and the EDF and other groups “have been advising Wal-Mart on its changes.” Clifford added:

The fund opened an office in Bentonville in 2007 so it could have direct access to Wal-Mart. It does not accept contributions from Wal-Mart or other corporations it works with.

What the article didn’t mention is that between 2003 and 2010, the latest year for which tax data are available, the Walton Family Foundation gave the EDF almost $39.5 million—and the funding ramped up around the time Wal-Mart launched its sustainability initiative. In 2009, the foundation’s gift represented roughly 13 percent of the fund’s total revenues.

Update: Shortly after press time, the Walton Family Foundation released its 2011 environment grants list, including a total of $13.6 million for EDF.

The Walton family, which created Wal-Mart, still owns a majority stake in the publicly traded corporation, and some of its members sit on the boards of, or are active in, both the company and the foundation. In addition, Sam Rawlings Walton sits on the EDF’S board.

Clifford, an admirable reporter, acknowledged the shortcoming in her article for the Times.

“This was simple oversight on my part and nothing more,” she wrote in an email. “I was writing on deadline, and checked that Walmart had not donated to the EDF, but I didn’t think to check the EDF board for Walton family members, or Walton Family Foundation donations. (None of the third parties I’d spoken to had mentioned that connection, which isn’t an excuse — I should have thought of it myself, but didn’t.) Had I been aware of it, I absolutely would have included it and I will in the future.”

Dr. Robert Brulle, a sociologist at Drexel University who studies funding relationships between environmental organizations and foundations, first caught the omission in the story.

“It seems to me that this information is highly relevant to this story and casts the relationship between EDF and Wal-Mart in a very different perspective,” he wrote to the Times’s public editor, Arthur Brisbane, in emails he shared with CJR. “I would hope that the NY Times would do a better job informing its readership of relations of this type.”

Indeed, journalists covering green business have the responsibility to find and report any possible conflicts of interest.

Jon Coifman, who works in the Environmental Defense Fund’s corporate partnerships program, said the group’s initial conversation with Clifford had to do with Wal-Mart’s progress report on its environmental goals, issued last week, and was not specifically focused on its ongoing relationship with Wal-Mart, which became the focus of the story.

“This is not to fault Ms. Clifford in the least,” Coifman wrote in an email. “We know as well as you do that stories evolve between reporting, writing and editing. Had we been aware of the ultimate emphasis at the time of the interview, however, we would have made a much stronger point of stressing this [funding] background in greater detail in order to avoid any trace of potential confusion with her, her editors, or her readers.”

“The Walton Family Foundation is not involved in EDF’s corporate partnerships work in general, or our work with Walmart in particular,” he added. “All of this is a matter of public record and has been widely discussed, as has the fact that Sam Walton is one of 39 members of the EDF Board of Trustees. (All trustees are required to recuse themselves from any vote or decision involving businesses with which they are affiliated.)”

It should also be noted that neither the Times nor the Environmental Defense Fund overlook Wal-Mart’s contemptible activities. On April 22, the paper ran a long, front-page article about how the company had orchestrated and hushed up “a campaign of bribery to win market dominance” in Mexico. And an exposé of Wal-Mart’s decidedly un-green supply chain in countries like China, which appeared in the March/April issue of Mother Jones, quoted an EDF representative criticizing the company’s operations overseas.

Curtis Brainard is the editor of The Observatory, CJR's online critique of science and environment reporting. Follow him on Twitter @cbrainard.