Loggers were stealing the forest. These women started stealing their chain saws.

The forest had given Doris Ofre everything.

When she was growing up in southern Nigeria, it was her family’s supermarket, pharmacy, and ATM. If her mother needed cash for her school books, she sold oranges and mangoes she picked in the forest. If they wanted adventure, Ms. Ofre and her friends played hide-and-seek beneath the tree canopy, and tossed bananas to the monkeys hanging in the branches.

So when the forest that had given her so much was threatened by illegal loggers, Ms. Ofre didn’t hesitate.

She picked up her machete, and with 20 other women, marched toward the scene of the crime.

Globally, the world’s forests are receding at a rapid clip, with more than 40,000 square miles disappearing annually, according to the United Nations. Nigeria is on the front lines of this crisis. The country has lost 13% of its tree cover since the year 2000, according to Global Forest Watch, which tracks deforestation around the world. In Cross River state, where Ms. Ofre lives, that loss is particularly consequential. With the state being home to half of Nigeria’s rainforest, communities there have long relied on the forests for their survival.

That’s why, in 2018, Ms. Ofre, who is a farmer, and five other women in Olum decided to form an informal forest policing squad to stop their forests from being chopped up and carried away. Armed with machetes, hoes, and the authority to name and shame locals who participate in illegal logging, they have helped vastly reduce the practice here, according to local authorities and environmental activists.

Because illegal logging is so lucrative, men in the community might have allowed it to continue, says Fredaline Akandu, the king, or paramount ruler, of the Boki district. “But women don’t tolerate it.”

The scramble for Boki’s trees

Ms. Ofre’s connection to the forest began early in life. She grew up in Olum, a farming village carved into the mountainous rainforest near Nigeria’s southeastern border with Cameroon. As a child in the 1960s and ’70s, she says, she was taught that the forest was her community’s wealth. The forest was where her family and neighbors went to cut down wood for their houses, taking only as much as they needed. Women collected vegetables there to cook with and sell.

However, beginning in the 1980s, Ms. Ofre began to notice the trees disappearing. It started with the growl of chain saws. Then huge trucks would appear at the edge of the forest. They arrived empty, but left loaded down with wood. Usually, the men cutting down the trees were locals working for outside companies. Occasionally, Ms. Ofre even saw people she knew personally.

Soon, they noticed other changes. Foraging for once-abundant wild mushrooms became a treasure hunt. The monkey population dwindled so much that when Ms. Ofre’s children were growing up in the 1990s, she had to take them to a nearby monkey sanctuary to see the animals at all.

The 16 villages surrounding the forest weren’t the only ones that recognized the problem. In May 2000, the state government established the Afi Mountain Wildlife Sanctuary in Ms. Ofre’s backyard. The reserve was meant to provide protection to the region’s several endangered species, including the Cross River gorilla, one of the world’s rarest great apes. It also prohibited logging anywhere in the park grounds.

But the carving up of the forest continued. Now, increasingly, Ms. Ofre saw Chinese loggers, who seemed to particularly like a swirl-patterned amber wood called bubinga.

In July 2012, the consequences of this scramble for Boki’s trees were laid bare when a landslide tore through Buanchor, one of the villages bordering Afi Mountain. It flattened houses and the local secondary school. The soil had become loose and exposed because of the logging, says Peter Bette, a local environmentalist. “It is possible we wouldn’t have had the landslide should the felling of trees not [have happened].”

Finally, Ms. Ofre and other women in the community could take no more. In 2018, a small group that included Ms. Ofre and local Queen Faith Akandu formed the Women Association of Afi Mountain Wildlife Sanctuary to fight back. They joined a growing cadre of community and conservation groups patrolling the forest. Some were searching for poachers, others wildfires.

But the Women Association was the first to specifically target illegal loggers.

Caught in the act

It began to scour the forest for felled trees and other traces the loggers left behind, which they reported to local authorities. Sometimes, though, the women happened to catch perpetrators in the act.

One day in May 2020, for instance, Ms. Ofre says she was home at her farm when she heard a chain saw roar to life in the distance. She and her colleagues followed the sound to its source: a local man cutting down a large tree. The women demanded he hand over his chain saw, and then they marched him to the king’s palace.

That kind of policing is possible in Olum because everyone knows everyone here, and families go back generations, locals say. That means if someone breaks the rules, they must either face the music or leave the community entirely.

“We see the Afi Mountain Wildlife Sanctuary as our oil. We don’t joke with it,” explains King Akandu, who is also a longtime environmental activist in the region. When the women bring him loggers, he warns or fines them, he says.

“The works of the women are effective, says Mr. Bette. “[In the past], anyone could jump into the forest to start cutting wood. But that has stopped in Olum and Buanchor.”

Now, the group is thinking bigger. It wants to expand its patrols to other communities around Afi Mountain, where it says many locals are cutting down trees themselves, and leaders have been bought off by logging companies. It’s tricky work, Ms. Ofre acknowledges. But she never thinks of giving up.

“We are protecting the remaining forest for our children so they will experience what we experienced,” she says. “I believe women always achieve their goals when they unite.”