Sky islands: That's what ecologists call tree-covered ranges that rise from surrounding desert and scrubland. It suits Maderas del Carmen, 515,000 acres (208,000 hectares) set aside for conservation in northern Mexico, part of a growing patchwork of protected Chihuahuan Desert lands along the U.S.-Mexico border. In these limestone mountains live 400 bird species (more than half the number commonly seen in the continental U.S.) and 70 mammal species, including one that's returning after a long absence, the desert bighorn sheep.
"The sheep were all shot out 60 years ago. It's a dream for us to reintroduce them," says Patricio Robles Gil, president of Agrupación Sierra Madre, a conservation group spearheading the project. In the past two years nearly 50 sheep have been brought from an island in the Gulf of California to a 12,000-acre (5,000-hectare) enclosure adjacent to Maderas del Carmen. "Once we build up a herd, we'll begin releasing them," he says.
Established in 1994, Maderas del Carmen remains largely privately owned ranchland. Robles Gil recently worked with Cemex, a Mexican cement company, to purchase 136,000 acres (55,000 hectares) within and bordering del Carmen that will be more strictly conserved.
The expanding range of another del Carmen resident illustrates the value of corridors of protected land. Black bears now wander into Big Bend National Park, where they'd been absent for decades.
A bear helped teach Robles Gil about balancing the needs of wildlife and humans. He once spent time with a rancher who refused to kill bears even when they killed livestock. "The rancher had a cowboy who raised pigs, and one day a bear killed one. The rancher said, ‘If the bears kill all ten of your pigs, come back and tell me.' The bears killed them all, and the rancher paid the cowboy for his losses."
—John L. Eliot