When Melissa Farlow was a little girl growing up in Paoli, Indiana, she was completely enamored with the idea of having a horse.

“I dreamed about them, I drew them in church, I played like I was a horse,” she says. She wanted a horse so badly that she even wrote to Roy Rogers asking if he would send her Trigger. He sent a signed autograph instead. But her parents finally caved, and at age six, she got a “sad, one-eyed pony,” as she describes it. “He wasn’t pretty, but he was docile, and I rode him around the backyard.”

Farlow, a contributing photographer to National Geographic, has now turned that childhood obsession into a photo-rich book called Wild at Heart: Mustangs and the Young People Fighting to Save Them. Written by Terri Farley, the book focuses on the plight of the feral mustangs that are at once a symbol of the American West and threatened by loss of habitat and controversial federal management programs.

Because the horses are wild, multiply fairly rapidly, and compete with privately owned ranch animals for limited resources, they don’t have many human protectors.

“These horses don’t make money for anybody. No one hunts them, no one breeds them, no one eats them,” says Farlow. “The only ones who advocate for them are the animal lovers—and it’s hard for them to compete and be activists.”

The history of wild horses in North America has been a complicated one. According to Farlow, horses roamed with woolly mammoths, then disappeared about 12 million years ago—possibly surviving extinction by crossing the Bering land bridge. They were reintroduced in the 1500s by European explorers, and more than two million of their descendants roamed the largely unfenced American West until the early 1900s.

Since then, expanded urbanization has encroached on their range, and today fewer than 30,000 remain—most squeezed onto public lands where wildfires, recurring droughts, and loss of habitat make life increasingly harsh.

And for decades wild horses that came too close to cattle or sheep on public grazing lands were seen as a nuisance and were often targeted for capture or slaughter. A woman named Velma Johnston, aka “Wild Horse Annie,” is credited with pushing for 1971 legislation that protected wild horses and burros from being captured or killed.

Today, the Bureau of Land Management (BLM) is the only agency authorized to manage wild horses on federal land, and according to Farlow they spend roughly $40 million annually caring for them. That includes conducting annual roundups that use helicopters to drive horses into corrals. The goal is to cull the herds and keep wild horses from multiplying beyond a sustainable level. Some young horses are made available for adoption, but there are few takers, and most end up in long-term holding facilities funded by the BLM.

Farlow says that due to these practices more wild horses now live in captivity than run free on public lands. So those who care about wild horses have a lot to contend with in their battle to keep them free roaming and prevent possible extinction.

Farlow and writer Terri Farley were particularly moved by individual young people who have taken up the cause of the wild horse, and the final chapter of the book focuses on some of their stories.

“I’m amazed by the convictions of these kids, and I am so proud of them—they are so committed to what they are doing,” says Farlow. “When I was young I don’t think I was focused on anything outside of my own little world. I’m amazed by their passion.”

And while Farlow shot a number of the photos in the book for a 2009 National Geographic magazine story, she made new images of the young people specifically for this book.

“Photographing teens and photographing horses was much the same. I didn’t expect that part,” she says. “They are shy when you first meet them. You have to be nonthreatening and spend enough time with them to feel like you are ‘getting them’—much like you do with horses.”

As a result of working on this project—spending time photographing horses in the wild, in sanctuaries, and with the people who love them—Farlow says her childhood obsession with horses has evolved into a newfound respect.

“I wasn’t aware there were wild horses [in North America] until I was working on a [National Geographic] story,” she says. “So few people out there realize there are wild horses, so I feel like this book is education not just for kids but for everyone. It needs to be out there for people to care about horses because that’s the only way [the horses] will be saved.”

Melissa Farlow is a documentary photojournalist who has worked extensively for National Geographic for more than 25 years. A Pulitzer Prize winner, she worked on the staffs of the Louisville Courier Journal and Pittsburgh Press. She consults for The Photo Society and is a frequent lecturer in professional and educational venues. She was recently inducted into the Indiana Journalism Hall of Fame.