Pablo Guerrero has been visiting cacti in the Atacama Desert his whole life, first on family trips to the Chilean coast and later as a researcher studying the impacts of climate change and illegal poaching on the fragile flora.

The desert, which is the driest spot on Earth beyond the planet’s poles, can be so desolate that NASA uses it to test Mars rovers. But from a young age, Guerrero learned to spot pockets of life hidden within the arid landscape.

Cacti, a smorgasbord of funky shapes and showy flowers, easily became his favorite.

Guerrero began visiting the Atacama as a researcher in the early 2000s and observed the plants of his childhood with a botanist’s eye. Their ability to flourish in such extreme conditions impressed him, and he grew concerned about their ability to continue surviving as humans infiltrated the desert.

“Encountering these plants, especially those facing conservation challenges, was almost an epiphany for me,” says Guerrero, now a botanist at the Universidad de Concepción in Chile.

Cacti in the Atacama are particularly vulnerable to disturbances. Many species live in only a few square kilometers. And in the driest reaches of the desert, cacti depend on fog alone for water. But the desert is getting hotter and drier, and in some places, the fog is disappearing.

Humans’ impact on the desert is increasing too. In Guerrero’s youth and earlier in his research career, the only way to access remote hotspots of biodiversity was to trek through the desert on foot. As the mining and energy industries began to grow, more roads were built, turning hours-long treks into quick drives.

Litter now pools along the roadside, Guerrero says. Once-bursting spots feel lifeless, haunted by the desiccated husks of cacti. Because the desert is so dry, remains are slow to decompose and linger for years. And many remaining cacti populations are sparse.

“Comparing today’s populations with historical photos that a botanist took, it’s easy to see the change in the presence of plants,” he says. “They’re much less abundant now.”

In recent years, Guerrero began hearing from colleagues about more cacti being seized at the Chilean border. Interest in having cacti as houseplants grew around the world — and so did cactus theft. From the American Southwest to South Africa, desert plants have been targets of plant poaching. Even the remote Atacama wasn’t safe.

How, Guerrero wondered, was poaching affecting the desert’s cacti?

He looked to Copiapoa, a diverse genus of cacti found primarily in the Atacama that has been “a hot commodity” in recent years. From his field visits, it seemed obvious that many species were threatened, if not already near extinction. In the most recent assessment, in 2015, 28 percent of Copiapoa species and subspecies were classified as critically endangered or endangered. But nearly half of the 39 known species and subspecies hadn’t been evaluated at all.

Guerrero first set out to correct this, using new evolutionary histories of the species, careful mapping and outside experts to reclassify Copiapoa’s extinction risk. The results were stark: 76 percent of all Copiapoa species and subspecies are critically endangered or endangered, dramatically more than what the 2015 assessment found.

Guerrero then analyzed factors of extinction risk, such as landscape condition, human footprint, plant poaching and legal trade to see which factors were most likely responsible for the increased extinction risk Copiapoa faces. Climate change played a role, but poaching and trade clearly stood out as significant, affecting almost all critically endangered species, he and colleagues reported in the October Conservation Biology.

“The situation is really bad,” Guerrero says.

Determined to help conserve the Atacama’s cacti, he is researching what keeps them alive in the desert and collaborating on state and international efforts to document poaching. He thinks creating new conservation areas with the greatest biodiversity and training park rangers to identify rare cacti are essential.

But the rapid rise of extinction risk for the Atacama’s cacti alarmed Guerrero. “I’m scared for the future of some of these species.”