Sierra Madre Occidental

The Sierra Madre Occidental is a mountain range that covers all of western Mexico and the extreme southwest of the United States. In its 1,500 km long it runs through Arizona, part of Sonora, Chihuahua, Sinaloa, Durango, Nayarit, Zacatecas, Aguascalientes, and Jalisco where it joins the Transversal Volcanic Axis of Mexico. The sierra has an extension of 289,000 km² and occupies the sixth part of the Mexican territory. Its width on average is 150 km, with heights of up to 3000 meters above sea level. Transversely, these mountains are crossed by the Chihuahua al Pacífico Railroad, a Tourist Train also called Chepe.

Climate

The terrain is rugged in many regions, making temperature variations extreme. At the top of the ravines, the climate is cold (arriving in winter at -20 °C and in summer at 20 °C on average), and in the valley temperate or warm (in winter 10 °C on average, reaching 40 °C in summer).

Flora and fauna

Landscape of the Sierra Madre Occidental.

Barranca de Huentitán in Jalisco, is the beginning of the Sierra Madre Occidental.

The Sierra Madre Occidental is the lung of the northern zone of Mexico; Covered by large mixed pine-oak forests, pine, holm oak and fir-oyamel, in recent years it has suffered serious deterioration. The chain is home to numerous endemic species, with a wide variety of flora and fauna. According to the 1994 Biodiversity Management of the Madrean Archipelago Report, up to that date the Sierra Madre Occidental had more than seven thousand species of plants, of which four thousand were endemic. While other forested areas of the world have only four or five species of pines in each ecosystem, in the Sierra Madre Occidental there are fifteen different ones, plus some 25 holm oaks. However, the immoderate logging of the last 120 years has considerably deteriorated the ecosystem, killing many species and putting others on the brink of extinction. Studies carried out by J. Martjan Lammertink, Jorge A. Rojas Tomé, Federico M. Casillas Orona and Roger L. Otto made it possible to determine that practically the entire forest of the Sierra Madre Occidental has been subjected to logging programs.

In the Sierra there are at least 517 species of fauna: 290 birds, 70 mammals, 87 reptiles, 20 amphibians and 50 fish. Among the mammals, the squirrel, the skunk , various species of bats, the coyote, the armadillo, the white-tailed deer, the weasel, the wild boar, the badger, the puma, the jaguar, the ocelot and the wild cat stand out. Although they are in danger of extinction, the puma and the black bear still exist in the most remote areas of the Tarahumara.

Of the birds, 24 species are endemic. 10 are in danger of extinction; among them, the green macaw, the mountain parrot, the coa, the golden eagle and the peregrine falcon. Certain studies also include the long-eared trogon, the spotted owl and the spotted jay among the endangered birds.

Of the reptiles, 22 species are endemic and of the amphibians twelve have that character. Among the freshwater fish, some of which are edible, the rainbow trout, Eleotris picta, the Cichlasoma beani and fish from the poeciliidae and Eleotridae families stand out.

Vegetation of the three zones in the sierra

Landscape of the Sierra Madre Occidental in Nayarit.

Upper Tarahumara

The Santiago River at its pass through the limits of the state of Nayarit and Jalisco; on the one hand, the Sierra Madre Occidental.

Potential vegetation

coniferous and encino forest (100%)

Average annual temperature

warm (4.92%), temperate (64.41%)

Precipitation

400 to 600 mm (16.99%), 600 to 800 mm (83%)

Humidity

semi-arid (6.81%), sub-humid (23.81%)