The diversity of physical and climatic environments has led to the development of very rich wildlife, both in form and in its adaptation to this arid region, typical of what is known as the Sonora Desert, one of North America’s four deserts. Four hundred and sixty-three species of flora have been found in the terrestrial part of the Reserve and 37 are known to be endemic to the geographical area in general. The greatest number of plant associations of the whole peninsula is concentrated in this region. Approximately 8.3% of the flora is known to be endemic to the geographical region of the El Vizcaino Desert.

The Biosphere Reserve contains three subdivisions of the Sonora Desert. The sub-Province “Vizcaino Desert” is the best represented, covering almost 95% of the area of the Reserve; the sub- Province “Gulf Coast” occupies a narrow strip along the eastern borders of the sierras to the east of the Reserve; and “Magdalena Region” only covers one percent. Its lagoon complex is the Gray Whale’s calving and mating site and harbours healthy populations of Mexicana Bighorn Sheep, Mule Deer, Puma, Coyote and 64 other species of mammals. It is also a refuge for 125 species of migratory birds and the transition zone between tropical and temperate climates.