An ecoregion is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas of land or water, and contain characteristic, geographically distinct assemblages of natural communities and species. The biodiversity of flora, fauna and ecosystems that characterise an ecoregion tends to be distinct from that of other ecoregions. In theory, biodiversity or conservation ecoregions are relatively large areas of land or water where the probability of encountering different species and communities at any given point remains relatively constant, within an acceptable range of variation . Ecoregions are also known as "ecozones", although that term may also refer to biogeographic realms.
A bioregion is an ecologically and geographically defined area that is smaller than a biogeographic realm, but larger than an ecoregion or an ecosystem, in the World Wide Fund for Nature classification scheme. There is also an attempt to use the term in a rank-less generalist sense, similar to the terms "biogeographic area" or "biogeographic unit". It may be conceptually similar to an ecoprovince. It is also differently used in the environmentalist context, being coined by Berg and Dasmann (1977).
The Chiapas Depression dry forests form one of the ecoregions that belong to the tropical and subtropical dry broadleaf forests biome, as defined by the World Wildlife Fund, in northwestern Central America.
The Chimalapas montane forests is a tropical moist broadleaf forest ecoregion in southern Mexico. It includes the montane tropical forests of the Chimalapas region on the boundary of Chiapas and Oaxaca.
!["Marine Ecoregions (Spalding 2007). [Map by] GEOMAR, University of Seville, Department of Human Geography"](https://web.archive.org/web/20170212110426/http://www.marineplan.es/ES/fichas_kml/mapasfichas/ecoregions.jpg){kind=link}
