South Portland resident Hannah Holmes has published four nonfiction, science-oriented books including “Quirk: Brain Science Makes Sense of Your Peculiar Personality,” “The Well-Dressed Ape: A Natural History of Myself” and “Suburban Safari,” which examined the inhabitants of her backyard (spiders, chipmunks and crows included). But the publication of “Quirk” corresponded with a general crash in the publishing industry, and Holmes now mostly makes her living selling real estate. We talked to the Maine native (her mother was one of the ’60s era back-to-the-landers) about carbon footprints, the locavore movement and sustainability, including the sustainability (or not) of the 21st-century writer’s life.

CAREER SHIFT: She’d written for National Geographic, Discovery and other magazines she admired. And there were four books, the last published by Random House in 2011. Yet after “Quirk” she started selling real estate. How did that transition come about? “It was a really weird time,” Holmes said. “Publishers had stopped doing any promotion of any title. Books were kind of just tossed out the door and left to sink or swim.” Her agent, she noted, hadn’t sold a single title in nine months. “It’s like you are a hairdresser and suddenly no one is getting their hair cut anymore,” she said. “Like an entire category of professions just went poof.” Real estate had long intrigued her, “but it didn’t feel like it was sufficiently save-the-world-y,” Holmes said. “But when the publishing industry went belly up, it seemed like an invitation.”

END OF THE LINE: Not that Holmes is a quitter, by any means. “It was the only thing I really knew how to do, and I held on to it for a really long time,” she said. “I had been so successful that it was really hard to give up, to be going back down the ladder and starting up a new ladder.” But her life as a nonfiction writer had become too much about making the mortgage and not enough about the things she cared about. Or quality. “I found myself sending story proposals to dumber and dumber magazines. So rather than contribute to the dumbing down of America, I decided to do something that I just thought was a blast.”

BETTER LUCK THIS TIME? Is real estate more financially rewarding as well as fun? “That is not saying much, but yes!” Holmes said. She enjoys the research about a building’s history and evolving neighborhoods. “The biggest surprise for me is how journalistic it actually turns out to be. To really prepare people for these huge decisions, it is helpful to give them a ton of information.” Like the truth about the lurking dust? (One of Holmes’ books is called “The Secret Life of Dust: From the Cosmos to the Kitchen Counter, the Big Consequences of Little Things.”) “It has come up, shall we say,” Holmes said. And while selling homes may not feel save-the-world-y enough, she does donate 10 percent of her net to a friend’s sustainability center in Haiti. “I stick that in there to balance it for myself.”

LOCAVORE ETHOS: What do you think of Maine’s local food movement? “Maine has always had a powerful streak of independence and self-reliance, and I suspect there is an element of that self-reliant perspective feeding this locavore ethos,” Holmes said. “It is a natural fit. Perhaps sticking out here in the Atlantic ourselves, we are accustomed to making do with what we’ve got, and as the national culture has grown more supportive, I think Maine has just proven to be fertile ground for the whole concept.”

BACK TO THE FUTURE: Your mother was part of the late ’60s wave of back-to-the-landers; how did that affect you? “I was an extremely reluctant back-to-the-lander,” Holmes said. Her mother had “an itty bitty farm” near Boothbay, which Holmes did not enjoy. “We would cut up pigs on our kitchen table,” she said. “That was my mother’s idea of fun.” But not hers. “It was embarrassing. It was dirty. It was endless (work). It was not remotely princess-y. Except for riding horses, I pretty much hated it all. My area of rebellion has always been to live in urban places and to make a point of not growing my own food.”

FROM THE SLUSH PILE: That’s not to say Holmes doesn’t think about where her food comes from. One of the book proposals she tried to sell after “Quirk” was about Thanksgiving. “I was going to produce a Thanksgiving dinner entirely from food produced within a mile of my place,” she said, even if it took running over a wild turkey. “The first Thanksgiving was about acknowledging our ability to extract food from the planet. And the book was going to be a measure of how far Thanksgiving as a holiday has drifted from that original concept. Now we get a turkey in the form of ice meat from Iowa and potatoes from Idaho. Thanksgiving has turned into this celebration of agribusiness, really.”

CARBON TURKEY FOOTPRINT: It is not poor quality that galls Holmes so much as it is what it takes to make and transport that food. “My body is not a temple. But my planet is definitely a temple so my interest in the subject rises from the potential for producing calories more efficiently, and efficiency in our economy is not reflected in the price of food because we subsidize transportation and all kind of agricultural inputs. Truly efficient food has to be produced locally and with minimal inputs from far away. So the calculator that is always running in my brain is how can you do this more simply and with a smaller carbon footprint?”

HOLMES’ WAY: Her contribution is: “I basically don’t purchase anything. I am not much of a consumer, but I am hyper-aware when I do purchase.” Down to a kiss: “The fact that there is a little piece of paper that comes in the Hershey’s kiss?” she said. “I am going to worry about it and I am going to separate it and recycle it. I am not proposing this for a lifestyle because it is very stressful.”

LAST WORDS? With all this passion for the planet, is Holmes really done with writing? When she quit, she said, “I was never going to type another word again.” But that feeling is starting to pass. She just wrote a piece for “O” magazine. And she just taped a TEDxDirigo talk.

“It is kind of fun to be tinkering with things again.”