Ecozone

An ecozone is the broadest biogeographic division of the Earth's land surface, based on distributional patterns of terrestrial organisms.

Ecozones delineate large areas of the Earth's surface within which organisms have been evolving in relative isolation over long periods of time, separated from one another by geographic features, such as oceans, broad deserts, or high mountain ranges, that constitute barriers to migration. As such, ecozone designations are used to indicate general groupings of organisms based on their shared biogeography. Ecozones correspond to the floristic kingdoms of botany or zoogeographic regions of zoology.

Ecozones are characterized by the evolutionary history of the organisms they contain. They are distinct from biomes, also known as major habitat types, which are divisions of the Earth's surface based on life form, or the adaptation of animals, fungi, micro-organisms and plants to climatic, soil, and other conditions. Biomes are characterized by similar climax vegetation. Each ecozone may include a number of different biomes. A tropical moist broadleaf forest in Central America, for example, may be similar to one in New Guinea in its vegetation type and structure, climate, soils, etc., but these forests are inhabited by animals, fungi, micro-organisms and plants with very different evolutionary histories.

The patterns of distribution of living organisms in the world's ecozones were shaped by the process of plate tectonics, which has redistributed the world's land masses over geological history.

Ecozone (WWF definition) Area Notes million square kilometres million square miles Palearctic 54.1 20.9 including the bulk of Eurasia and North Africa Nearctic 22.9 8.8 including most of North America Afrotropic 22.1 8.5 including Sub-Saharan Africa Neotropic 19.0 7.3 including South America, Central America, and the Caribbean Australasia 7.6 2.9 including Australia, New Guinea, New Zealand, and neighbouring islands. The northern boundary of this zone is known as the Wallace line. Indo-Malaya 7.5 2.9 including the Indian subcontinent, Southeast Asia, and southern China Oceania 1.0 0.39 including Polynesia (except New Zealand), Micronesia, and the Fijian Islands Antarctic 0.3 0.12 including Antarctica.

6 of the 8 ecozones according to the WWF   Nearctic   Palearctic   Afrotropic   Indomalaya   Australasia   Neotropic   Oceania and Antarctic ecozones not shown.

The Palearctic and Nearctic are sometimes grouped into the Holarctic ecozone.

The World Wildlife Fund scheme is broadly similar to Miklos Udvardy's system, the chief difference being the delineation of the Australasian ecozone relative to the Antarctic, Oceanic, and Indomalayan ecozones. In the WWF system, The Australasia ecozone includes Australia, Tasmania, the islands of Wallacea, New Guinea, the East Melanesian islands, New Caledonia, and New Zealand. Udvardy's Australian realm includes only Australia and Tasmania; he places Wallacea in the Indomalayan Realm, New Guinea, New Caledonia, and East Melanesia in the Oceanian Realm, and New Zealand in the Antarctic Realm.

Bioregions

The WWF scheme further subdivides the ecozones into bioregions, defined as "geographic clusters of ecoregions that may span several habitat types, but have strong biogeographic affinities, particularly at taxonomic levels higher than the species level (genus, family)." The WWF bioregions are as follows:

• Afrotropic
• Antarctic
• Australasia
  • Australia
  • New Caledonia
  • New Guinea and East Melanesian Islands
  • New Zealand
  • Wallacea
• Indomalaya
  • Indian subcontinent
  • Indochina
  • Sunda Shelf and Philippine Archipelago
• Nearctic
  • Canadian Shield
  • Eastern North America
  • Northern Mexico and Southwestern North America
  • Western North America
• Neotropical
  • Amazonia
  • Caribbean
  • Central America
  • Central Andes
  • Eastern South America
  • Everglades
  • Northern Andes
  • Orinoco
  • Southern South America
• Oceania
  • Micronesia
  • Polynesia
• Palearctic
  • Asia
    • East Asia north of the Himalayan system's foothills to the arctic
      • Himalayan
      • Tibetan Plateau steppe
      • Yunnan-Guizhou Plateau
      • Northeast Asia
      • Russian Far East
    • Central Asia - Iranian Plateau and north to the arctic.
      • Temperate Asia biocountry
      • Mongolian Plateau
      • Eurasian Steppe
      • Asian Russia (central)
        • Asian-Siberian region
    • Western Asia
      • Arabian desert
      • Mediterranean Near East (Roughly corresponds to the Levant)
      • Anatolian Plateau
      • Transcaucasia
  • Northern Africa
    • Atlantic coastal desert
    • Sahara desert
    • Mediterranean Maghreb
    • Atlas montane
  • Europe (Northern, Middle, Eastern, Southwestern, and Southeastern Europe biocountries) - Mediterranean to the arctic.
    • European Mediterranean Basin
    • Iberian Peninsula
    • North Caucasus
    • Alps montane
    • Carpathians
    • Scandinavia
    • European Russia
    • Euro-Siberian region
  • Macaronesia

See also

• Cosmopolitan distribution
• Ecotone

References

• Dinerstein, Eric; David Olson; Douglas J. Graham; et al. (1995). A Conservation Assessment of the Terrestrial Ecoregions of Latin America and the Caribbean. World Bank, Washington DC.

External links

• BBC Nature - Ecozones