Ecozone

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Ecozones are global divisions which have their own characteristic interplay of climatic factors, morphodynamics, soil-forming processes, living conditions for plants and animals, and production potentials for agriculture and forestry. Correspondingly, they are distinguished by different climates, landforms, soil units, plant formations and biomes, and land use systems. In the (hierarchical) systems of natural regions, whose basic unit is the ecotope, the term ecozone represents the highest class heading. A few of the ecozones are subdivided into comparatively independent subregions or ecoregions, such as the Polar subpolar zone, which is divided into the glacier-covered regions (ice deserts), the frost debris regions and the tundra. Some of these ecorgions are further subdivided into eco-provinces and eco-districts (in this hierarchical order).

Contents 1 Ecozones 2 Biogeographical realm 3 History 4 References

[edit] Ecozones

According to Schultz (1988, 2000, 2002 and 2005) nine ecozones can be defined:

1. Polar subpolar zone
2. Boreal zone
3. Temperate (or Humid) midlatitudes
4. Dry (or Arid) midlatitudes
5. Subtropics with winter rain (or Mediterranean-type subtropics)
6. Subtropics with year-round rain (or Humid subtropics)
7. Dry tropics and subtropics (or Tropical/subtropical arid lands)
8. Tropics with summer rain (or Seasonal tropics)
9. Tropics with year-round rain (or Humid tropics)

These ecozones occur in bands, often fragmentated because of the distribution of the continents and oceans, from the poles to the equator. Nearly all are present in both the Northern and Southern Hemispheres (see below).

The classification system of ecozones in the manner described can aid in establishing an orientation guide which allows immediate listing of several important characteristics of any area on earth; and is suitable as a basis for further detailed investigation.

[edit] Biogeographical realm

A biogeographical realm or ecozone is a biogeographical and ecological land classification system of the world first formally proposed by Miklos Udvardy in 1975 for conservation purposes. Arguably, biomes are better suited for conservational purposes.

The boundaries of an ecozone are often the result of plate tectonics as a region is biologically isolated for a long period leading to unique fauna and flora.

8 biogeographical realms with unifying features of geography, fauna and flora are defined.

• Nearctic 22.9 mil. km² (including most of North America)
• Palearctic 54.1 mil. km² (including the bulk of Eurasia and North Africa)
• Afrotropic 22.1 mil. km² (including Sub-Saharan Africa)
• Indomalaya 7.5 mil. km² (including the South Asian subcontinent and Southeast Asia)
• Australasia 7.7 mil. km² (including Australia, New Guinea, and neighbouring islands). The northern boundary of this zone is known as the Wallace line.
• Neotropic 19.0 mil. km² (including South America and the Caribbean)
• Oceania 1.0 mil. km² (including Polynesia, Fiji and Micronesia)
• Antarctic 0.3 mil. km² (including Antarctica)

Udvardy originally further divided the biogeographic realms into 203 biogeographical provinces (floral "regions" and faunal "provinces").

Intensive regional analyses of biodiversity patterns across five continents and biogeographical realms have been used by the World Wildlife Fund to define the boundaries of terrestrial ecoregions for the Global 200.

The biogeographic realms are also supporting current natural World Heritage sites.

Among zoologists, Nearctic and Paleartcic together make up the Holarctic zone, as these two zones have often been connected by the Bering land bridge and thus have very similar mammal and bird fauna.

[edit] History

The systems of biogeographical regions started with Augustin de Candolle in 1820. In his study Essai Elementaire de Geographie Botanique he was very interested in documenting the nature and floral composition, also known as biomes. He was the first author to define endemic areas.

It was only after the acceptance of Darwin's theory of evolution that Adolf Engler associated the development of different floras to different regions of the world. His studies on biogeographical regions were based on de Candolle's climatic and physiological studies. Engler's four regions included the temperate and cold regions of the northern hemisphere; the old world tropics; extending from Africa to northern Australia; most of Central and South America; and coastal Chile, Tierra del Fuego, the Cape region and south coast of South Africa, most of Australia, Tasmania, the South Island of New Zealand, and the islands in the southernmost Atlantic, Indian and Pacific Oceans.

In 1908, Diels placed New Zealand in the Palaetropical Realm and subdivided the "Ancient ocean" Realm in four Realms. Nineteenth-century zoologists also contributed to the biogeographical schemes. Philip Sclater recognized six regions in 1858 based on passerine bird distributions. Alfred Russel Wallace introduced biogeographical regions based on mammal distributions, and these remain in acceptance by the scientific community.

[edit] References

References:

• Schultz, J.: Die Ökozonen der Erde, Ulmer Stuttgart, 3rd ed. 2002 (1st ed. 1988). ISBN 3-8252-1514-8
• Schultz, J.: Handbuch der Ökozonen, Ulmer Stuttgart 2000. ISBN 3-8252-8200-7
• Schultz, J.: The Ecozones of the World, Springer, Berlin Heidelberg New York, 2n ed. 2005. ISBN 3-540-20014-2 und ISBN 3-540-20014-7
• Udvardy, M. D. F. (1975). A classification of the biogeographical provinces of the world. IUCN Occasional Paper no. 18. Morges, Switzerland: IUCN.