Role of the Global Ecoregions and how they are selected

The central tenet of underlying the 238 ecoregions selected as Global Ecoregions is simple: only by identifying a comprehensive representation of the world's habitats can we conserve the broadest range of species and maintain the complex ecological and evolutionary processes that comprise the web of life.

Although an estimated 50% of all species occur within one habitat type (tropical rainforests), the other half of all species are found elsewhere in the world's land, freshwater, and marine environments. To conserve these, we must embrace full representation of the world's diverse ecosystems. 

By selecting outstanding examples of each ecoregion type, from each biogeographic realm and ocean basin, the Global Ecoregions analysis ensures balance and representation in a global biodiversity strategy.

Other less biologically diverse areas are also critical components of a global strategy. Tundra, tropical lakes, mangroves, temperate broadleaf forests all are unique expressions of biodiversity. Although they may not support the rich species assemblages seen in tropical rainforestsor coral reefs, they contain biological communities adapted to distinct environmental conditions and reflect different evolutionary histories. To lose examples of these communities would represent an immeasurable loss to future generations.

The Methodology for Selecting The Global Ecoregions

The Global Ecoregions are the results of regional analyses of biodiversity across the continents and oceans of the world, completed in collaboration with hundreds of regional experts worldwide and by conducting extensive literature reviews.

These ecoregions were chosen from outstanding examples of each terrestrial, freshwater, and marine major habitat type. The 26 major habitat types describe different areas of the world that share similar environmental conditions, habitat structure, and patterns of biological complexity, and that contain similar communities and species adaptations.

In order to represent the unique fauna and flora of the world's continents and ocean basins, each major habitat type was further subdivided by 7 biogeographic realms (Afrotropical, Australasia, Indo-Malayan, Nearctic, Neotropical, Oceania, Palearctic).

Finally, ecoregions that represented the most distinctive examples of biodiversity for a given major habitat type were identified within each biogeographic realm. They were chosen based on the following parameters:

• species richness
• endemism
• higher taxonomic uniqueness (e.g., unique genera or families, relict species or communities, primitive lineages)
• extraordinary ecological or evolutionary phenomena (e.g., extraordinary adaptive radiations, intact large vertebrate assemblages, presence of migrations of large vertebrates)
• global rarity of the major habitat type

Only the biodiversity value of ecoregions sharing the same major habitat type were compared because the relative magnitude of parameters such as richness and endemism varies widelay among them.