Gordon Fleming is, by his own account, an environmentally sensitive guy.

He bikes 12 1/2 miles to and from his job at a software company outside Santa Barbara, Calif. He recycles as much as possible and takes reusable bags to the grocery store.

Still, his girlfriend, Shelly Cobb, feels he has not gone far enough.

Cobb chides him for running the water too long while he shaves or showers. And she finds it “;depressing,”; she tells him, that he continues to buy a steady stream of items online when her aim is for them to lead a less materialistic life.

Fleming, who says he became committed to Cobb “;before her high-priestess phase,”; describes their conflicts as good-natured—mostly.

But he refuses to go out to eat sushi with her anymore, he said, because he cannot stand to hear her quiz the waiters. “;None of it is sustainable or local,”; he said, “;and I am not eating cod or rockfish.”;

As awareness of environmental concerns has grown, therapists say they are seeing a rise in bickering between couples and family members over the extent to which they should change their lives to save the planet.

In households across the country, green lines are being drawn between those who insist on wild salmon and those who buy farmed, those who calculate their carbon footprint and those who remain indifferent to greenhouse gases.

“;As the focus on climate increases in the public's mind, it can't help but be a part of people's planning about the future,”; said Thomas Joseph Doherty, a clinical psychologist in Portland, Ore., who has a practice that focuses on environmental issues. “;It touches every part of how they live: what they eat, whether they want to fly, what kind of vacation they want.”;

While no study has documented how frequent these clashes have become, therapists agree that the green issue can quickly become poisonous because it is so morally charged. Friends or family members who are not devoted to the environmental cause can become irritated by life choices they view as ostentatiously self-denying or politically correct.

Those with a heightened focus on environmental issues, on the other hand, can find it hard to refrain from commenting on things that they view as harmful to Earth—driving an oversize SUV, for example.

Sandy Shulmire, a psychologist who lives in Portland, confesses that when she is visiting her sister in Abita Springs, La., she cannot resist bugging her about not recycling her plastic and cardboard, even though she knows she will be perceived as “;bossy.”;

Cherl Petso, an editor of an online magazine who lives in Seattle, says trips to visit her parents in Idaho can be “;tense at times,”; in part because she and her mother interpret each other's choices as judgmental.

If Petso prepares a vegan meal for the family, her parents prepare hot dogs to go alongside. Her parents serve on throwaway Styrofoam plates; she grabs a plate that can be cleaned and reused. Her mother, who says she prefers the way food tastes when it is served on Styrofoam, notes that washing dishes has its own environmental costs.

Linda Buzzell, a family and marriage therapist for 30 years who lives in Santa Barbara and is a co-editor of “;Ecotherapy: Healing with Nature in Mind,”; cautions that the repercussions of environmental differences can be especially severe for couples.

“;The danger arises when one partner undergoes an environmental 'waking up' process way before the other, leaving a new values gap between them,”; Buzzell said.

Changing the family diet because of environmental concerns can be particularly loaded, Buzzell added. She warns wives and mothers not to move a family toward vegetarianism before everyone is ready.

“;Food is such an emotional issue,”; she said.

Christienne deTournay Birkhahn, executive director of the EcoMom Alliance, an organization based in Marin County, Calif., that provides education to women who want to have their families live more sustainably, finds that disputes over how green is green enough often divide along predictable lines by sex.

Women, Birkhahn said, often see men as not paying sufficient attention to the home. Men, for their part, “;really want to make a large impact and aren't interested in a small impact,”; she said.

That is certainly the case in her own marriage, she said. Her husband, Kurt, an engineer and federal employee, sometimes seems to be baiting her by placing plastic yogurt cups in the garbage or leaving the reusable shopping bags in the car and coming home with disposable bags instead.

In the ensuing discussions, Birkhahn said, her husband argues that the changes she is making may have a large effect on their lives but have little or no effect on the planet. He fought every step of the way against the gray-water system she installed in their bathroom to recycle water to flush the toilet, calling it a waste of time and money, she said. The system cost $1,200 to install.

Birkhahn said she found it hard to dispute his point but thought it was irrelevant. “;I am trying to be a role model for my son,”; she said.

Buzzell suggests that couples can overcome such differences if they treat each other gently. She advises partners who have a newfound passion for the issue to change only a few things at a time and provide lots of explanation.

“;It is like exercise,”; Buzzell said. “;Take it slowly.”;

Still, Robert Brulle, a professor of environment and sociology at Drexel University in Philadelphia, said he had seen divorces among couples who realized that their values were putting them on very different long-term trajectories.

“;One still wants to live the American dream with all that means, and the other wants to give up on big materialistic consumption,”; Brulle said. “;Those may not be compatible.”;

Fleming, in Santa Barbara, said that he was not quite at that point, but that he was drawing some firm lines.

He continues to make purchases on eBay—although he immediately breaks down the delivery boxes and puts them in the recycling bin to “;avoid scrutiny.”;

And unless Cobb can make peace with his long, hot showers, the issue may someday be a deal breaker.

“;I like to see the water pouring down,”; he said, sounding utterly unrepentant.