Robles developed a simple website and Facebook page, but mostly relied on word of mouth to attract ecotourists and hunters. He spelled out his vision in a brochure filled with photos of wildlife and people in workshops. "We pursue to create an ecological paradise, but we are also committed with the community," the brochure says. "We seek to be a leading example for the world's conservation practices, instilling in people the ecological values to help them learn how to live in balance with nature, and set up the perfect environment for research projects. We aim to establish a sustainable model that protects biodiversity, supports other landowners, teaches and helps the community."

For several years in the 2000s, Robles' hunting and ecotourism business drew increasing numbers of customers. They stay in La Casona, or the big house, a brick-and-cement ranch compound built in the 1960s that can accommodate 15 people comfortably -- and up to 35, if some are willing to sleep outdoors. Virtually all of his customers have come from the U.S.

Two hunters from the Phoenix, Ariz., area are regular customers, paying $4,500 each to bag Coues white-tailed deer. They say they were attracted by the ranch's spectacular beauty as well as by its deer, which they describe as healthier than those on most Arizona lands. "There is a very important pride of ownership in this property -- you can tell whenever you see Carlos and listen to him speak about his land and his dreams for the ranch," says Joe Del Re of Chandler. Robles' conservative harvest quota and grazing management allow many deer to reach trophy class, says the other hunter, Charles Kelly of Scottsdale.

Tom Wood of the Southeastern Arizona Bird Observatory says he's taken birdwatchers from all over the country to Aribabi to glimpse gray hawks and green kingfishers -- birds that are much rarer in the U.S. A single birdwatcher staying at Aribabi pays $89 for one night and about $350 a week, including meals; couples and larger groups pay less per person.

But starting around 2008, Robles says, his income from ecotourism and hunting plunged 60 percent. Customers from the U.S. are increasingly fearful of being caught in the cartel violence; according to Wood and hunters Kelly and Del Re, that's a larger factor than the generally sagging economy. All three say they've seen no safety problems near Aribabi. But Wood, who has not led a birding trip to Aribabi in more than two years, says, "Until people feel comfortable traveling in Mexico again, it will be kind of hard to make a living in ecotourism."

Three longtime birdwatching guides who work in Sonora and other parts of Mexico -- Borderlands Tours and High Lonesome Tours, both based in Arizona, and Solipaso in Alamos, Sonora -- say they've also seen a major dropoff in ecotourism due to fears of violence. Mexico has been a mainstay for 25 years for Borderlands owner Rick Taylor, but in 2011, for probably the first time, he didn't run a Mexico tour, he says. He cancelled seven tours to Chiapas, Veracruz, Oaxaca and San Blas, among other places, after getting only a handful of inquiries.

Most of the cartel violence -- the headline-making decapitations and machine-gun shootouts -- occurs many miles away from Robles' ranch, in cities hugging the border, especially Juárez (across the river from El Paso, Texas) and eastward. And most of the victims are cartel members, law enforcement or immigrants headed for the U.S. -- an increasing sideline for the cartels. Even so, the average murder rates in Sonora and Chihuahua are higher than in Arizona, the Arizona Republic reported recently.

In February, the U.S. State Department issued the latest in a series of warnings to U.S. tourists, reporting that the cartels killed nearly 13,000 people in the first nine months of 2011 alone. "While most of those killed in narcotics-related violence have been members of (cartels), innocent persons have also been killed. The number of U.S. citizens reported to the Department of State as murdered in Mexico increased from 35 in 2007 to 120 in 2011. ... U.S. citizens have fallen victim to ... homicide, gun battles, kidnapping ... Carjacking and highway robbery are serious problems in many parts of the border region and U.S. citizens have been murdered in such incidents. ... In addition, local police have been implicated in some of these incidents." Few of the 150,000 U.S. citizens who cross the border on an average day are targeted, but nevertheless, the State Department warned: "You should defer non-essential travel" in Chihuahua and parts of Sonora and Baja.

Warnings like that, and sensationalized U.S. news stories, have whipped up fears even in places in Mexico that are not gripped by violence. "Americans are scaredy-cats -- now they're worried that a ricocheting bullet from the border south of Texas might hit them 1,000 miles south of Tucson," Taylor says. "Sure, a mass execution is a horrible thing. But who are the victims? They are El Salvadoran and Guatemalan immigrants (or cartel soldiers). We provide the market (for the cartels' drugs and immigrant workers), we provide the weapons (guns from U.S. sellers), and we provide the media attention when drug cartels do anything awful."

For Solipaso, fears of violence have reduced hotel reservations by 50 percent in the past two years and birdwatching by 25 percent, says Jennifer MacKay, who has run the business with her husband, David, for 12 years. "I get so many emails from (potential) visitors, asking, 'Is it safe?' " says MacKay. "We have guests who travel all over with my husband and then come here for a couple of nights and find out it is totally fine and (the danger has been) blown out of proportion."