But the risk of violence has also worried U.S. conservation groups that work in Sonora and Chihuahua. The Tucson-based Sonoran Institute pulled back for several years from a restoration project it had been working on along the Santa Cruz River in Sonora -- about 20 miles from Rancho El Aribabi -- after a former employee living there warned about the risks. Last fall, the Sonoran Institute resumed the project, this time in partnership with Sky Island Alliance, after the same person said it was safe "if you practice caution." As the Sonoran Institute's Emily Brott says: "Don't drive at night. Don't go alone."

Staffers for five other U.S. groups working in Northwest Mexico say they haven't cut back operations due to the violence. But they have to go through a lot more checkpoints on the roads now, as various Mexican lawmen search cars for guns and other evidence. And one of the groups, Defenders of Wildlife, has stopped taking donors on visits to sites in Northwest Mexico. A conservation rancher in Chihuahua says, "There was a murder near my ranch a few weeks ago. Just cartel-to-cartel, but I heard the gunshots. And then dead bodies were found about 15 miles from my ranch." Farther south, a few Mexican environmentalists and government environmental officials have been kidnapped or murdered in the last two years.

"Definitely, conservation has been hard hit" by fear of the cartel violence, says Ernesto Enkerlin, who ran one of Mexico's top conservation agencies, Comisión Nacional de Áreas Naturales Protegidas, or CONANP (which manages federal conservation areas), from 2001 to 2010. Although many U.S. groups are hanging in there in Mexico, Enkerlin's sense is that some groups and researchers "are now afraid" of traveling in Mexico, or "they're concerned about liability and not letting their people come into Mexico" as much as they used to, or "they're reluctant to invest in (Mexican) projects where bad things might happen."

Mexico's system of conservation relies a great deal on ranchers like Robles and other landowners, because there's relatively little government land devoted to conservation. (See sidebar describing more ranches and Mexico's system of conservation.) "There can be no conservation in Northwest Mexico if it doesn't involve landowners," says Enkerlin, who's now with Monterrey Tech University. The conservation ranchers are doubly impacted as the cartel violence discourages some U.S. groups and results in "less income from hunting and ecotourism." Ranchers like Robles "are exactly the kind of people we need more of," Enkerlin says. "It's really sad."

In late 2010,  the U.S. Fish and Wildlife Service nominated Robles to be part of a new binational jaguar recovery team. In early 2011, the Mexican agency CONANP formally recognized Robles' ranch as a "protected natural area" -- the country's second-highest status for conserved land. The program allows Robles to keep that status even with cattle back on his land. It raises the profile of his conservation efforts, but probably won't lead to much federal funding. "In theory, there are benefits," Enkerlin says, "but things are happening much slower and with much less resources than we imagined" when the program was ramped up in 2007. And the federal designation of Robles' ranch as an UMA, so he can manage deer and sell hunts, came with no funding, Robles says.

Robles says he needs $40,000 to $50,000 a year to maintain the ranch and keep it safe from intruders. He has applied for a grant from a different Mexican program that pays ranchers for providing ecosystem services, such as healthy watersheds, but has yet to receive a response. Enkerlin, who helped create that program in 2003, says it's also very short of funds; it's been increased to $80 million a year from $30 million in the first year, but "that's not enough" spread across all the acreage of ranches and other private and communal land in Mexico. "The incentive is very small compared to the pressure" to run cattle and build subdivisions.

Mexican conservation groups tend to be smaller and have fewer resources than their U.S. counterparts. The key Mexican conservation groups active in Sonora and Chihuahua -- ProNatura and Naturalia -- say they aren't able to help Robles. He keeps hoping to get direct financial support from Sky Island Alliance, but that group says it doesn't provide subsidies for ranchers. Later this year, though, Sky Island Alliance will start a three-year restoration effort on Aribabi and four other Sonoran ranches, building more erosion-control structures and planting vegetation along creeks -- an effort financed with a $189,000 grant from the U.S. Fish and Wildlife Service, combined with $650,000 the group raised.

Sky Island staffers say they believe that, sooner or later, Robles will again remove the cattle from the land. "Carlos and his family are really amazing models -- they're rock stars in terms of conservation," says Melanie Emerson, the group's executive director. "It's a tough, tough road that they've chosen, they've made personal sacrifices, and we applaud them."

Robles even has plans to expand, by building more cabins for tourists and applying for more Mexican federal grants. He's also begun making charcoal out of dead mesquite trees, for another trickle of income. And despite the financial hardship, he has continued to keep two key areas entirely cattle-free -- the Río Cocóspera riparian area and Cañon de las Palomas, where jaguars have been photographed.

"The human race needs to see and do things differently, and show the new people that we can change the way of living," Robles wrote in an email. Otherwise, he said, "the human race goes straight into a big hole with no way to return."

This story was funded by contributions from High Country News readers and the High Country News Enterprise Journalism Fund.

Tony Davis is the environmental reporter for the Arizona Daily Star in Tucson. He's written dozens of stories for HCN since the 1980s, on a range of topics including water, livestock grazing and mining. You can contact him at tdavis789@yahoo.com. Ray Ring, HCN senior editor, contributed to the story.