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Adriana Carillo hikes through Arizona’s Huachuca Mountains with a black scarf around her neck, and she carries a walking stick. It’s March 2021, and it’s snowing. The sun hasn’t yet risen, but Carillo is surrounded by grasses and shrubs coated in a delicate layer of white fluff. The borderlands mountain range is part of the extraordinary Sky Islands. At nearly 4,500-foot elevation, the cool and isolated mountains harbor diverse species unlike those found in the hot desert ecosystem below. A month earlier, authorities had captured on camera an ocelot roaming the region.

But the 63-year-old isn’t there at 4 a.m. to investigate endangered wildlife. She’s braving the steep terrain alongside 11 others to look for Ariagne, a 23-year-old mother and migrant whose group abandoned her 15 days earlier on their way to the U.S. after she could no longer walk. The group travels some 10 miles but doesn’t find her. It’ll take the crew, which includes two of Ariagne’s relatives, another six attempts over nine months to complete their mission.

By the time they do, all that’s left of her are her clothes, shoes, hair, and bones.

The tragic scene is still a success story in Carillo’s line of work. The nonprofit she cofounded in 2020 and leads as president is called SOS Búsqueda y Rescate (in English, SOS Search and Rescue), the only border and migrant-focused search-and-rescue group run by a woman. Most of the time, the group works in the extreme heat of the desert, but sometimes this work leads them to the brisk mountaintop.

Since 2020, the team of volunteers has found about 60 survivors and the remains of 65 others. The organization has 27 open cases: migrants whose souls remain trapped along the border. Every person found — often by returning their remains to loved ones — represents closure for a family.

Ariagne left behind a 3-year-old daughter, a husband, and two sisters. As a mother and sexual assault survivor, Carillo has a deep sense of understanding of the women she encounters, be it the victims or their family members.

“We don’t know when someone close to us will be next in search of the American dream,” Carillo said in Spanish. “It’s not the American dream. What many find is death.”

Record-breaking heat means more deaths

As the southwestern U.S. gets rocked by nonstop record-breaking heat, the work of people like Carillo is becoming more and more critical. This year, heat has killed over 100 migrants along the border territories. In 2022, authorities found more than 890 bodies — a record number.

Rising temperatures caused by global warming directly affect humanitarian organizations’ ability to do this work. Even the cactuses have been crumbling from summer 2023’s soaring temperatures, which spiked over 110° Fahrenheit. According to Climate Central’s Climate Shift Index, climate change made those hot conditions in the Southwest at least five times more likely.

Carillo’s team drives overnight to Arizona from Los Angeles to begin their searches by 4:30 a.m. so that they can be done by 11 a.m. If they get caught in the desert past then, they have to wait in the shade until about 3 p.m. to avoid the worst of the sun’s heat.

“The heat is preventing us from responding to reports,” Carillo said. “We can’t help everyone.”

And global warming is driving all sorts of weather changes — from drought to hurricanes — that are fueling migrations and ripping families apart as some brave the journey north to find the income to support their families back home in Latin America.

There’s little research on the ways the climate emergency is affecting people trying to cross the border, but a landmark study published in the peer-reviewed research journal Science in 2021 found that global heating will likely kill more migrants along the U.S.-Mexico border in the coming decades. The authors looked at how much more water migrants will need as temperatures rise — a valuable resource that’s also heavy, making it hard to carry through the desert terrain.

Most migrants can carry only a gallon or two. They need about two gallons to withstand current temperatures. By 2050, the average person will need a third more water given the region’s expected temperature increases. The researchers found that an adult pregnant woman will need the most water: 3.6 gallons by 2050.

Carillo and her team always bring extra water in case they find someone alive. They even leave some water jugs behind in the shade so migrants can replenish themselves. The group tries not to worry too much about themselves, especially when it comes to the heat. “The climate is extremely hot, especially in the deserts, but we do this work because we are thinking about saving a life,” Duarte Reyes, one of the organization’s other co-founders, said in Spanish. “It doesn’t matter to us if we have to walk hours, just hoping to have the good outcome of finding our migrant brothers and sisters. I don’t think about the danger we face ourselves.”

A personal story of survival

This work is personal to Carillo. Her own story is one of survival — and it’s the story of all humanity as the planet reaches temperatures humans have never seen before.

Carillo was born in Trigomil, a quiet pueblo in the Mexican state of Nayarit not far from the Pacific coast. Here, farmers grew rice and sugar cane. She would wash her clothes in the spring and take the cows for a drink. Her family would gather water from the well and cook their meals over burning wood. The day’s end often involved work: selling milk or making cheese.

Carillo was five when her parents moved the family to the state capital, Tepic, where her father took a job transporting food to the border near Tijuana. Her mother was a seamstress, including sewing the children’s school outfits. In Trigomil, there was a school but no teachers. “We had to go to the capital to study,” Carillo said.

She stayed in the city until she was 19 and moved to Baja California with her husband and daughter. Her other two daughters were born in the years after the move. After she and her husband separated, she worked three jobs: one with the government during the day, then at a restaurant, and at a club overnight. She would sleep two to three hours, often heading home at 3 a.m. and waking up by 5:30 a.m. to get her girls ready and drive them to school. It was a vibrant life with enough money that she bought a house.

Everything changed the night she was assaulted.

She had just celebrated her 31st birthday when on her way home from work one night, four men robbed her and raped her. After the attack, she decided to leave for the U.S. with her daughters because her attackers threatened her, demanding she stay quiet.

With her passport and visa, she and her children were able to settle down in Los Angeles. However, she couldn’t enter the country again after leaving alone to finalize some paperwork back home in Mexico. That’s when she did what any mother would do: She attempted to cross the border over and over — a total of four times — until she could return to her daughters.

Much of her humanitarian work in the extreme heat is driven by a sense of sisterhood. Women increasingly make up the people who arrive in the U.S. In 2011, women composed only 13% of the migrants border agents would encounter. By 2019, that number nearly tripled to 35%.

“I put myself in the shoes of all the women who cross the border and are violated,” Carillo said. “I know what that is. I’ve already lived through it.”

Francesca Rodriguez, a 64-year-old who volunteers with SOS Búsqueda y Rescate, crossed illegally into the U.S. from El Salvador. Carillo’s work as a survivor has resonated with her. “She’s suffered a lot, and yet she still gives to others,” Rodriguez said. “She has a noble heart.”

Most of the people who call Carillo looking for their family members are women, too. She recognizes that though men play an important role in her field of work, especially during search and rescue missions, women have a warmer way of handling these situations.

“The man is stronger to walk through the desert,” Carillo said, “but for us women, our strength comes from being mothers and knowing our children are missing.”

In August 2023, the sister of a migrant called her, begging for help. Carillo went into action mode: She drove to Tucson to pick up Carla, a 17-year-old mother, and the 10-month-old girl she brought with her. The pair was trying to reach family in New Jersey. When Carillo got to the hotel where she was staying, the first thing she did was hug the young mom. She promised to send her on a plane to unite with her sister in New Jersey.

“I didn’t expect anyone to care enough about me to help me get home,” Carla, the migrant mother, told Carillo. She kept her head down, fearful that the authorities would take her baby girl and never give her back.

“I’m a mom first,” Carillo told her. “My organization is here to help people like you no matter what you need.”

“I have no way to pay you,” Carla responded.

“We don’t do this for money,” Carillo said. “We do it to keep our people safe.”

In April 2023, the team won an award for National Crime Victims’ Rights Week from the Department of Justice, which recognizes groups that care for crime victims. In this case, the victims are the migrants left abandoned by human traffickers — people like Ariagne, who died in the remote Huachuca Mountains.

Reyes often tells Carillo that she shouldn’t head into the desert anymore.

“She’s not a young lady anymore, but she doesn’t care,” he said. “She walks with us like any other young woman or man. I tell her, ‘You can move mountains if you want to.’ That’s who she is.”

But Carillo can’t do this work alone. She relies on higher powers to keep her and her team safe whenever they enter the desert mountains. Before stepping on the sacred sands where so many souls remain missing, she closes her eyes, holds both hands up and prays, not only to God but also to Mother Earth. “Mama Pacha, we ask for permission to enter your lands. Guide us and lead us.” And with that, her search begins.

To help support Carillo’s work and learn more about SOS Búsqueda y Rescate, click here.

Yessenia Funes is a journalist who has covered the climate crisis and environmental racism for a decade. She's editor-at-large for Atmos, an independent magazine. She also publishes a creative climate...