WWF has identified ecoregions - collectively known as The Global 200 (but are actually 233 regions), which are crucial to the conservation of global biodiversity. The goal of this new classification is to ensure that the full range of ecosystems will be represented in regional conservation and development strategies.
WWF reflected that though conservationists focused on the preservation of rainforest because they harbored an estimated 50 percent of species on Earth, a more comprehensive strategy for conserving global biodiversity could try to consider as well the other 50 percent of species and the ecosystems that support them. Several habitats, such as Mediterranean-climate shrublands, are on average more threatenend than tropical rainforest, and require conservation action. WWF claims that although conservation action typically takes place at the country level, patterns of biodiversity and ecological processes (e.g., migration) do not conform to political boundaries.
Two of the worldwide classification systems commonly used nowadays were outlined by Myklos Edvardyin 1975. The biogeographical realms (dividing the Earth's surface into heigt zones, and the biome system (which classify the world into ecosystem types).
Global 200 reflects major innovations compared to that classification system. It uses ecoregions as the unit of scale for comparison. The WWF defines an ecoregion as a relatively large unit of land or water containing a characteristic set of natural communities that share a large majority of their species, dynamics, and environmental conditions (Dinerstein et al. 1995, TNC 1997). WWF say ecoregions could be considered as conservation units at regional scale because they meet similar biological communities.
Based on a complete list of ecoregions, Global 200 includes all major habitat type, all ecosystems types, and species from every major habitat type. It makes a focus on each major habitat type of every continent (such as tropical forest or coral reefs).
Among all the ecoregions, some particular ones were selected over others, that were defined as sharing the same Major Habitat Type and Biogeographical Realm. Decision rules for selection of the Global 200 relied on extensive studies of 19 terrestrial, freshwater, and marine major habitat types. Selection of the ecoregions was based on analyses of species richness, species endemism, unique higher taxa, unusual ecological or evolutionary phenomena, and global rarity of major habitat types.
Global 200 ecoregions list can mostly help conservation at regional scale (local deforestation, destruction of swamps habitats, degradation of soils...). However, certain phenomenoms (such as bird or cetaceans migration) obviously depends of more complicated parameters not used in defining current database (such as atmospheric currents, dynamic pelagic ecosystem...). These would require further gathering of information, and require coordination of efforts between several ecoregions. However, Global 200 ecoregions can help this efforts, by identifying habitat sites, resting sites for migratory animals. it may also help identify origin of invasive species, and offer leverage for slowing down or stoping the intrusion and settling of thes latter.
The Global 200 present a list of 233 ecoregions, which include 136 terrestrial, 36 freshwater, and 61 marine ecoregions.