With President Obama facing mounting criticism over a lack of diversity in his recent Cabinet selections, his upcoming decisions to fill key energy and environment slots are being portrayed by some as opportunities to add women and minorities to his lineup.

Obama's initial nominations for his second-term Cabinet are all male and all white: Sen. John Kerry (D-Mass.) to replace Hillary Rodham Clinton at the State Department, Chuck Hagel as secretary of Defense and Jack Lew to lead Treasury. Labor Secretary Hilda Solis also announced her resignation this week; a replacement has not yet been named.

The homogeneity of the recently announced nominees sparked criticism this week, marked in part by a photo on the front page of Wednesday's New York Times of the president surrounded by a coterie of advisers, all of whom were white men. Senior adviser Valerie Jarrett was the only woman in that photo, and only her legs were visible.

Rep. Charlie Rangel (D-N.Y.) yesterday called the lack of diversity "embarrassing as hell" in an interview on MSNBC. Sen. Jeanne Shaheen (D-N.H.), in a separate interview on the network, called the opening round of nominations "disappointing" and said she hoped Obama would pick women for some of the remaining slots.

White House spokesman Jay Carney dismissed those concerns earlier this week, hinting that yet-to-be-made appointments would round out a diverse Cabinet.

"These stories are in reaction to a couple of appointments. I think it would be useful to wait and make judgments about this issue after the president has made the totality of appointments that he will make in the transition to a second term," Carney said during his daily briefing Wednesday.

Observers are suggesting that recently announced or expected vacancies at U.S. EPA and the departments of Energy and the Interior will be filled by candidates who are racial minorities or women. The Interior and Energy secretaries are Cabinet members, putting them in the line of presidential succession; the EPA administrator is a Cabinet-level position.

"I think these second-level Cabinet offices are going to have to be fairly diverse to offset the lack of diversity at the top level," said one left-leaning energy policy expert close to the administration.

"Of those three jobs [at EPA, DOE and Interior], at most one of them will go to a white guy," the source added, requesting anonymity to speculate on unannounced personnel moves.

EPA Administrator Lisa Jackson has announced that she will be leaving in the coming weeks, and Energy Secretary Steven Chu is widely expected to soon announce his resignation. Ken Salazar's fate atop Interior is less clear, but he may depart later this year. There is not a white man among the three -- Jackson is the first African-American to lead EPA, Chu is the first Asian-American in his post and Salazar is the second Hispanic Interior chief.

"We think it's important for the Obama administration to continue what has been their track record of having a diverse Cabinet," said Kim Freeman Brown, interim executive director of Green for All, a group that focuses on low-income and minority communities. "We've seen the success they've had, particularly on the energy and environmental issues. It's kind of an if-it's-not-broke-don't-fix-it paradigm."

Brown praised Jackson's emphasis at EPA on environmental justice concerns and said she hopes the next administrator -- whatever his or her background -- "continues the track record that Lisa Jackson had in championing those who have been overburdened by pollution."

Other large environmental groups, such as the Natural Resources Defense Council, do not have a position on diversity in itself, said Bob Deans, a spokesman for the group. But "there were some obvious benefits to having Lisa Jackson as EPA administrator given her background," he added.

As a New Orleans native and an African-American woman, "she understood the importance of environmental justice, for example. Understood certain communities, income groups have been subjected to adverse environmental conditions for many decades because they're exposed to toxic chemicals in the air they breathe, in the water they drink," Deans said.

Among the names that have circulated for those posts, former Sen. Byron Dorgan (D-N.D.), floated as a replacement for Chu at DOE, is seen as perhaps the only white man who could be nominated, given the likelihood that he would breeze through confirmation hearings, is well-versed in a variety of energy policy issues and comes from a state in the midst of an oil boom, sources suggest.

The need for diversity may make it more difficult for other white men vying for posts, such as Stanford University's Dan Reicher or former Colorado Gov. Bill Ritter (D), who are seen as potential DOE secretaries, or EPA Deputy Administrator Bob Perciasepe or Connecticut energy and environment commissioner Daniel Esty, who are seen as possible Jackson replacements. Perciasepe will serve as acting EPA administrator until a permanent successor is confirmed.

Women and minorities whose names are circulating may have a leg up, including, for EPA, former Washington Gov. Chris Gregoire (D), EPA air chief Gina McCarthy, California Air Resources Board Chairwoman Mary Nichols and former Pennsylvania Environment Secretary Kathleen McGinty. Gregoire and McGinty also have been floated as possible Energy secretaries, along with Susan Tierney, who withdrew from consideration for a deputy secretary post at the start of the Obama administration, and former Michigan Gov. Jennifer Granholm (D).

If Salazar decides to leave, Rep. Raúl Grijalva (D-Ariz.) is seen as a leading candidate to take the job.

The administration is keeping its cards hidden on upcoming personnel announcements, and it remains a distinct possibility that whoever is picked will be a surprise from academia or the private sector.