: The mountain range, once a hide-out for Apache Indians and gun-slinging outlaws, surges out of bone dry desert. Its lower rolling flanks are grasslands and its peaks are dense forests of firs and spruce - not unlike the Rocky Mountains.

El Carmen is one of the most unique and biodiverse ecosystems in North America, home to at least 400 plant species, 220 bird varieties, more than 50 mammals and with 64 reptiles and amphibians species also recorded.

The McKinneys, who worked for the Texas Parks and Wildlife Department, crossed over the river a year ago to join an unusual project to manage and preserve El Carmen.

It's unusual because it is not the government but one of Mexico's largest corporations - the world's third largest cement maker Cemex - which is driving the plan that will effectively create a private national park.

"We had a great life in the Big Bend National Park, but we used to dream of working in these mountains. They are so beautiful, so unique; so when we got the chance, we jumped at it," said Virginia-born Bonnie McKinney.

Cemex, whose industry is not the most environmentally friendly as it scrapes up huge quantities of raw materials that are then used to create concrete urban jungles, is giving something back to Mother Earth.

El Carmen, a collection of huge private ranches in Coahuila state stretching over 800 sq mile (2,000 sq km) or about half the size of Rhode Island, was designated a national park by Mexico in 1994, which put an end to logging and mining.

Cemex has under its control about a quarter of the national park after buying up two huge tracts and agreeing to manage and preserve another 50,000 acres (20,000 hectares) with another local landowner.

The Monterrey-based company would love to look after all of El Carmen, which is so remote the endangered Mexican black bear has found a last refuge there and is healthily reproducing.

FOCUS ON WHOLE ECOSYSTEM

The McKinneys lead a dozen young environmentalists living permanently at a base camp at the foot of the mountain range and just outside the El Carmen national park.

"So many wildlife projects focus on one species. This one focuses on the whole ecosystem," said Bonnie McKinney at the camp, a seven-hour drive across desert from the gritty northern Mexican industrial city of Monterrey.

"This whole area has been mined, logged and overgrazed. No one had the resources to set up a conservation project. It took a different line, like the input from Cemex, to get this project started," she added.

First stages of the project were to clean up El Carmen - tearing down barbed wire and fence lines from the area's bygone cattle ranching days. Massive overgrazing of delicate desert grasses has meant vast areas have lost their seed banks - rebuilding the seed bank is also on the project agenda.

The project workers currently are making a baseline inventory of all the fauna and flora in the national park, counting all the species of mammals, birds, reptiles and plant life they find at El Carmen.

Many species are endemic such as the Carmen white-tailed deer and the cliff chipmunk. Others are threatened such as the northern harrier, jaguarundi and the Texas horned lizard.

In the future, a permanent exhibition about the national park will be set up and further research on its flora and fauna will be encouraged.

Plans are to allow Cemex clients to visit the park - throwing in horse riding and hiking tours - and low density ecotourism might also be allowed for the general public, said Armando Garcia Segovia, Cemex's executive vice president of development.

"It cannot be a place for very intensive visits because ecosystems are fragile," Garcia said. "We have to find a way of allowing visits but with a certain degree of care."

"The end result should be a world class place for people to visit," said Billy Pat McKinney.

HUNTED TO EXTINCTION