Sierra Gorda: Biological Jewel

Beginning at an elevation of 900 feet (300 meters), the lowest regions of the Sierra Gorda Biosphere Reserve are arid and receive as little as 13 inches of rainfall per year.
Yet four different types of vegetation flourish here, and there is a wealth of plant and animal species. This is one of the oldest and most stable deserts in Mexico. It is estimated to have existed for some 50 million years.

The southern-most portion of the Chihuahua desert extends into the southwest portion of the biosphere reserve. It is an area that escaped the reach of glaciers during previous ice ages. As a result, it is considered to be one of the continent's most ancient and important deserts – serving as a seed bank, or germ plasm reserve – that has helped repopulate desert regions to the north with native species. Many important species remain to be discovered by researchers in this little-explored territory.

Rivers flow down from the highlands into the desert, carving vertical-walled canyons that reveal limestone strata. Fanciful rock formations loom over head, and crystal-clear springs gush from the river beds, despite the arid nature of the environment.