The biosphere of the Tehuacán Valley, located in southwestern Puebla state, is the largest biosphere on the planet and one of Mexico’s richest regions in vegetation. The federally protected Tehuacán-Cuicatlán Biosphere Reserve straddles the states of Puebla and Oaxaca, running 211 km. southwest of Tehuacán, a city of 200,000 people, to to the smaller municipality ofCuicatlán in Oaxaca. Located in the rugged Sierra Madre del Sur, massive mountain ranges surround the extensive valleys of Tehuacan and Zapotitlán and the Cuicatlán canyon. Most of the reserve forms part of the high basin of the Papaluapan River, one of the mightiest rivers in the country, fed by streams that are born in the mountains of the Sierra de Tehuacán and the Sierra Mixteca.
The city of Tehuacán enjoys a semiarid climate with an average anual temperatura of 18.6º C, a cool climate and an annual precipitation of 479.5 mm. It is notable that the valley’s rainwater is absorbed slowly into the soil, without much runoff, resulting in substantial quantities of calcium, magnesium, and potassium left in the soil. The Tehuacán Valley experiences 6 to 8 dry months, freezing temperatures from November to February, and even hailstorms in April and May. A mix of dry, humid, temperate, and warm weather makes for a variety of microclimates in the biosphere.
The extensive Tehuacán-Cuicatlán Valley has been designated as a single global biogeographic unit with a large variety of habitats and vegetation, with many species threatened and in danger of extinction. Name a biosphere reserve in 1998, this zone has more than 3,000 plant species, including many varieties of cactus. The range of vegetation types includes scrublands of spiny shrubs and cactus, low elevation deciduous forests, and pine and oak forests. The area boasts more than 25 species of cactus, including agave. Single plants can have as many as 11 different uses.
The fauna of Tehuacán is less diverse than the flora, and includes ants, termites, serpents, black and green iguanas, lizards, rabbits, squirrels, hares, and birds like woodpeckers, quail, doves, owls, hummingbirds, buzzards, swallows, and falcons.
Among the vertebrates, we find a variety of amphibian, reptiles, bats, and burds. Nearly 10% of the species have introduced from other continents or other regions of the country like green guacamaya; the rest are native species of which 50% are endemic, including the royal eagle.