They contain one or more core or nuclear zones, true wilderness areas designated for the strongest degree of long-term conservation protection; only research relevant to conservation and perhaps limited, low-impact tourism are allowed in these zones.

Surrounding or adjacent to buffer zones are transition zones, where local communities may live and, usually with training from conservation agencies, engage in sustainable uses of natural resources. (Sustainable means using plants and animals in ways that are economically profitable for the local economy yet not ecologically harmful; use, in other words, that will not lead to significant ecosystem damage or to decline in biodiversity).

Yet while conservationists hope to build a biodiversity corridor from Sian Ka’an to the Calakmul Biosphere Reserve in the middle of the Yucatan Peninsula, which would ensure that large animals such as the jaguar would have enough room to roam, there is growing recognition that the local indigenous people have to materially benefit from conservation efforts. 

2) Celestun and Rio Lagartos Biosphere Reserves These two coastal reserves in the north of the state of Yucatan contain extensive mangrove forests and salt flats of vital importance to marine life, resident birds (including Mexico's only flamingo population) and migratory shorebirds and waterfowl. El Cuyo, has been designated a priority area for migrant and wintering shorebirds, while Celestun is considered the fourth-largest wintering ground for ducks in the Gulf region.

The beaches of both reserves are important nesting areas for endangered sea turtles. 
3) Calakmul Biosphere Reserve, Campeche

Calakmul Biosphere Reserve is Mexico's largest protected area of tropical evergreen forest--more than a million-and-a-half acres of habitat for countless species of plants, animals, insects and resident and migratory birds.