Stop reading now. Don’t watch this film.

If a powerful global industry has its way, that’s what you’ll do. Because if you keep reading or – worse yet – go to the theater and watch the documentary “Cowspiracy,” you’ll be exposed to a dirty little secret of modern environmental politics.

In this new film, screening Thursday in South Portland and Oct. 20 in Bangor, filmmakers Kip Andersen and Keegan Kuhn begin their investigative journey with a simple question: Why do mainstream environmental groups such as Greenpeace, the Rainforest Action Network and the Sierra Club ignore one of the world’s worst polluters, the animal agriculture industry?

Or more to the point: Why don’t these groups campaign against hamburgers and hot dogs? How come they don’t promote plant-based, vegetarian meals?

Andersen, who narrates “Cowspiracy: The Sustainability Secret” and conducts the on-camera interviews, told me by phone from his office in Santa Rosa, California, that before he and Kuhn decided to produce the film, he tried to find the answers as “an everyday citizen.” But he got nowhere.

“I felt like the only way to ever get through to them was by saying, ‘I’m doing a film on sustainability,’ ” Andersen said. And although Greenpeace still refused to speak with him, Andersen did have better luck with other groups once a camera was involved.

The audience follows along as Andersen, with an unassuming demeanor and wearing a baseball cap, calls, emails and visits with staffers at leading environmental nonprofits, where the discussions tend to be awkward and confusing.

In a feature-length film that is by turns eye-opening, heart-wrenching and haunting, Andersen and Kuhn contend that these environmental groups are too timid, ill-informed or marketing-driven to tackle the sacred cow of meat-eating. The Daily Californian calls the film “incredibly gripping,” The Huntsville Times in Alabama labels it “quirky,” and The Huffington Post says “it’s making the beef industry uneasy.”

The film begins after Andersen watches “An Inconvenient Truth,” Al Gore’s 2006 documentary about climate change and is inspired to retool his life. He starts biking everywhere, switches out his lightbulbs and begins taking short showers.

But then a friend’s Facebook post shows him there is more to the story. The link leads to a United Nations’ report that cites livestock as the No. 1 source of greenhouse gas emissions.

As the film unfolds, Andersen learns little of substance from the environmental staffers about the connection between diet and pollution, and so he turns to writers, scientists and deep thinkers to help explain what’s going on behind the scenes.

Michael Pollan, author of the best-seller “The Omnivore’s Dilemma,” speculates that the environmental groups won’t touch the subject of meat-eating because “they focus-grouped it and it’s a political loser.”

Later, we hear about Sister Dorothy Stang and the more than 1,100 activists killed in Brazil in the past 20 years for speaking out against ranchers who clear-cut rainforests to graze cattle. Finally, the filmmakers report that the FBI targets animal rights activists as terrorists because they pose a threat to corporate profits.

This film doesn’t show graphic images of slaughterhouses or factory farms (instead we witness the slaughter of one backyard duck and the sad eyes of the cows on a sustainable dairy farm).

Former mega-cattle rancher turned animal activist Howard Lyman (who was sued, unsuccessfully, by the National Cattlemen’s Beef Association after an appearance on the “Oprah Winfrey Show”) tells Andersen that by publicly asking the film’s core question he’s put a target on his back.

The film’s original funder apparently felt targeted.

In the midst of filming, Andersen gets a call saying that the financial backer is pulling out because of the “controversial” nature of the film. The filmmakers then launch a crowd-funding campaign that meets its goal within four days and ultimately raises more than $100,000 (peanuts as far as film budgets go, but very successful for a crowd-funding campaign).

Two decades after I wrote a college thesis titled “How Environmental Groups Portray the Risks of Meat Consumption,” I was disappointed to see the same nonprofits evading Andersen’s questions (just as they had mine). But when I spoke to Andersen, he gave me hope that this film is opening people’s eyes.

Now that the film is being screened, “incredible things are happening,” he said.

He and Kuhn are editing a 50-minute version for schools.

“Already, we’ve seen changes within the (environmental groups),” Andersen said. “The Rainforest Action Network is now posting facts from our film on their Facebook. They’ve been posting images with the tagline ‘Think Green, Eat Green.’ ”

Andersen and Kuhn are planning a follow-up film documenting the “Cowspiracy” response.

Maybe this is one conspiracy that’s about to be cracked?

Avery Yale Kamila is a freelance food writer who lives in Portland. She can be reached at:

[email protected]

Twitter: AveryYaleKamila

ANOTHER VEGETARIAN EVENT

WHAT: Plant-Based Family Workshop: Veg Food for Kids

Learn how to raise a vegetarian family, while sampling plant-based food. Workshop leader Marie Elizabeth Coyle discusses nutrition, school lunches, picky eaters and shopping on a budget.

WHEN: 2 to 4 p.m. Oct. 18

WHERE: Greater Portland YMCA, 70 Forest Ave., Portland

HOW MUCH: Free

INFO: [email protected]