Optimism and nonviolent communication are not the kinds of talking points one might expect to hear from a vegan activist. But Mercy for Animals President Leah Garcés, 41, exudes nothing but calm during a break from a convention for animal rights activists in the Washington, D.C., suburbs.

This conciliatory tone — reflected in her new book, Grilled: Turning Adversaries into Allies to Change the Chicken Industry — has drawn criticism from purists, but Garcés has receipts in the fight to ease animal suffering, even if they come from the inside of America’s food giants.

After leading a whistleblowing documentary revealing troubling practices at Perdue Farms chicken houses, she has gone on to work with the company on a number of reforms. She has negotiated animal welfare policies at Chipotle and Panera Bread, and she sits on an advisory board for Ben & Jerry’s ice cream. Her most recent campaign, the website ChickieLeaks.com and a series of billboards in Georgia advertising it, encourages people in the industry to blow the whistle on unsavory practices.

The left wing of the bird and the right wing of the bird are still part of the same bird.

Craig Watts, poultry grower who worked with Leah Garcés

Born in Spain but raised in Orlando, Garcés became a vegetarian at 15 and was involved in politics early — the class president from fifth grade through the end of high school. “One year I tried to be secretary, and I spelled ‘secretary’ wrong on the posters and realized that I’m not a detail-oriented person, I’m a vision-oriented person.” Her goal was to be a vet while studying zoology at the University of Florida. But after publishing a senior thesis on environmental impacts on alligators — it turned out pollution was turning them hermaphroditic — her professor took her aside. “You don’t want to be a vet. You want to get to the root of the problem, but vets are fixing the animals once they are broken already,” he told her.

That revelation led her to King’s College London, where she earned a master’s degree in sustainable development that was rare at the time. While animal rights were disorganized and still nascent in the U.S., it was thriving in the U.K at the turn of the century (there is even a political party dedicated to the cause). She went on to Compassion in World Farming and the World Society for the Protection of Animals, where her work ranged from opposing bullfighting in Spain, to protecting dolphins extracted from Fiji to perform in Mexico, to fighting bear bile farming in Asia.

Garcés had to temper her emotions — because the movement there was both more mature and more British. But by the time she was 30 and had seen “every type of suffering possible” across 30 countries, it was difficult to remain patient and even-keeled. So when she returned to the United States in 2009, partly for her husband’s new job with the Centers for Disease Control and Prevention in Atlanta, she nearly joined the fervor of America’s far more heated animal debate. (In one example from around this time, PETA staged a supermarket meat aisle installation made up of “human” limbs wrapped in plastic wrap; meat-eaters were told they were “chewing and swallowing the skin and muscle of a murder victim.”)

“I got mad that things weren’t happening faster,” Garcés says, but she realized “there was a lot of anger without a lot of insight … I realized my first job wasn’t to expose the chicken industry, but just to find out what the hell was happening.” No activist had launched an exposé into the practices of chicken factories in at least a decade. She reached out to pasture chicken farmers first since they treat their animals better than most. It turned out that the farmers disliked “Big Chicken” too: The major companies often landed farmers in tremendous debt.

Soon after, she met Craig Watts, a poultry grower in North Carolina who signed a contract in 1992 for four chicken houses with Perdue, the third-largest poultry integrator in the United States. Perdue owned the chicken, told him what to do with it and what he had to buy to keep up with changes. “I was having issues with very sick birds being delivered to me. I was really frustrated with how they were treating the farmers,” he says. Partnering with Garcés, Watts became a central figure in a documentary film that got coverage in The New York Times. Now he is hoping to switch his chicken houses to a new product, potentially mushrooms.

“She didn’t judge me for what I was doing, no more than I judged her for what she was doing,” Watts says. “The left-wing of the bird and the right-wing of the bird are still part of the same bird.”

It was Garcés’ breakthrough moment … and while Perdue initially resisted change, she now has a working relationship with the company. “Jim Perdue was the villain in my video,” she says. But within two years, she met the company chairman in person and had productive discussions on the company’s reduced-meat future. “Our vision is to be the most trusted name in premium protein,” Jim Perdue told Bloomberg last year. “It doesn’t say premium meat protein, just premium protein.”

The company has since started putting windows in its chicken houses and created its first animal care policy, while also moving to a more humane way of killing through controlled atmosphere stunning — steps that Garcés pushed for. “She is really straightforward and respectful of the differences of opinion — consistent and persistent,” says Dr. Bruce Stewart-Brown, senior vice president of Food Safety & Quality Live Operations at Perdue Farms, traits he adds have been “definitely in the minority” from the company’s critics.

In winning those concessions, Garcés — whose nonprofit now boasts 120 staffers across the world — had to accept that a complete retreat from meat won’t happen immediately. And many activists see her work as consorting with the enemy. Mercy for Animals “is a classic example of a welfarist organization that makes a habit of talking out of both sides of their mouths, and of saying one thing while doing another,” writes Linda McKenzie, an Australian blogger who criticizes Garcés’ organization for creating standards that “allow the consumer to choose the level of animal torture they wish to purchase.”

Garcés says such criticism is part of a “punitive purity culture” in which “people confuse sitting down [with opponents] as letting go of your morals.” Still, she is excited about the progress she has seen.

As the rise of “blended meats” or the recent viral success of Burger King’s Impossible Whopper has shown, consumers might be willing to make less meat-heavy choices … if they were given a fighting chance. Garcés imagines a world where her three children aren’t burdened with determining what food is good or bad for animals and the world at large. “Where you walk in the store, and it’s just good,” she says. It’s a dream that could have tremendous ramifications for not just the way we live and eat, but also the way we preserve a planet where more greenhouse gases come from farm animals than planes, trains and automobiles combined.

Read more: The CEO funding the alt-meat market.