The Biosphere Reserve is characterized by its size, good state of conservation and continuity with other regions in the Yucatán Peninsula, Chiapas, Guatemala and Belize. It is considered to be the largest forest mass in Mexico and, together with the forests of Guatemala and Belize, the second largest remnant forest left in Latin America after the Amazon. Its great diversity of species responds to regional heterogeneity, where in spite of its scant land forms, high and medium altitude sub-evergreen (moist) forests, medium altitude sub-deciduous (dry) forests (with a predominance of Holywood Lignum-vitae (Guaiacum sanctum)); lowland deciduous forests and savannahs can be found.

This group of forests harbours Mexico’s largest populations of fauna and flora, comprising charismatic or flagship species of biological and ecological importance for the region, such as the Jaguar, the Puma, the Tapir, the White-lipped Pecary, the Howler Monkey and the Spider Monkey, the King Vulture, the Ornate Hawk together with Mahogany, Cedar and Ciricote trees. There are also endemic species of economic and ecological importance for the region such as the Ocellated Turkey (Meleagris ocellata) Gray Brocket Deer (Galindo-Leal, 1999). Ninety percent of the amphibian species and over 50% of the reptile species reported for the Peninsula are to be found in the region. The land area is very important for birds with over 360 species recorded and it is also considered to be an important geographical area for Neotropical migratory species. (Galindo-Leal, 1999; Berlanga and Wood, 2001).