Ecozone

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6 of the 8 ecozones according to the WWF
  Oceania and Antarctic ecozones not shown.

An ecozone or biogeographic realm is the broadest biogeographic division of the Earth's land surface, based on distributional patterns of terrestrial organisms. They are subdivided in ecoregions, which are classified in biomes or habitat types.

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.

Concept[edit]

It should be noted that the traditional physiognomical concepts of ecozone (Schültz, 1995, which is more similar to the concept of biome) and ecoregion (Bailey, 1976) are not exactally equal to the concepts used in the Global 200/WWF scheme (Olson & Dinerstein, 1998 - originally, it was used the term "biogeographic realm" of Udvardy, 1975), which also includes floristic criteria (see de:WWF-Ökoregion). Furthermore, the term ecozone was also used before in stratigraphy (Vella, 1962, Hedberg, 1971).[1][2][3][4]

Udvardy (1975) biogeographic realms[edit]

The hierarchy of the scheme is (with early replaced terms in parenthesis):[4]

  • biogeographic realm (= biogeographic regions and subregions), with 8 types
    • biogeographic province (= biotic province), characterized by a major biome or biome-complex
      • biome, with 14 types

Schültz (1995) ecozones[edit]

Schültz (1995) defined nine ecozones:[1]

  • 1. polar/subpolar zone
  • 2. boreal zone
  • 3. humid mid-latitudes
  • 4. arid mid-latitudes
  • 5. tropical/subtropical arid lands
  • 6. Mediterranean-type subtropics
  • 7. seasonal tropics
  • 8. humid subtropics
  • 9. humid tropics

Global 200 / WWF ecozones[edit]

Main article: Global 200
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 Trans-Saharan Africa and Arabia
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.

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

The World Wildlife Fund scheme[3] is broadly similar to Miklos Udvardy's system,[4] 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.

See also[edit]

References[edit]

  1. ^ a b Schültz J. 1995. The Ecozones of the World: The Ecological Divisions of the Geosphere. Berlin: Springer-Verlag.
  2. ^ Bailey, R. G. 1976. Ecoregions of the United States (map). Ogden, Utah: USDA Forest Service, Intermountain Region. 1:7,500,000.
  3. ^ a b Olson, D. M. & E. Dinerstein (1998). The Global 200: A representation approach to conserving the Earth’s most biologically valuable ecoregions. Conservation Biol. 12:502–515.
  4. ^ a b c Udvardy, M. D. F. (1975). A classification of the biogeographical provinces of the world. IUCN Occasional Paper no. 18. Morges, Switzerland: IUCN, [1].

Bibliography[edit]

  • 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[edit]