Biogeographic realm

A biogeographic realm or ecozone 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.

The realms delineate the 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, biogeographic realms designations are used to indicate general groupings of organisms based on their shared biogeography. Biogeographic realms correspond to the floristic kingdoms of botany or zoogeographic regions of zoology.

Biogeographic realms 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 realm 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 biogeographic realms were shaped by the process of plate tectonics, which has redistributed the world's land masses over geological history.

6 of the 8 biogeographic realms
  Oceania and Antarctic ecozones not shown.

Concept history

The "biogeographic realms" of Udvardy (1975) were defined based on taxonomic composition. The rank corresponds more or less to the floristic kingdoms and zoogeographic regions.

The usage of the term "ecozone" is more variable. It was used originally in stratigraphy (Vella 1962, Hedberg 1971). In Canadian literature, the term was used by Wiken (1986) in macro level land classification, with geographic criteria (see Ecozones of Canada) (Wicken 1986, Scott 1995). Later, Schültz (1988) would use it with ecological and physiognomical criteria, in a way similar to the concept of biome.

In the Global 200/WWF scheme (Olson & Dinerstein 1998), originally the term "biogeographic realm" in Udvardy sense was used. However, in a scheme of BBC (n.d.), it was replaced by the term "ecozone".

Terrestrial biogeographic realms

WWF / Global 200 biogeographic realms (BBC "ecozones")

The World Wildlife Fund scheme (Olson & Dinerstein 1998, Olson et al. 2001) is broadly similar to Miklos Udvardy's (1975) system, the chief difference being the delineation of the Australasian realm relative to the Antarctic, Oceanic, and Indomalayan realms. In the WWF system, The Australasia realm 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.

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 realm.

Morrone (2015) biogeographic kingdoms

Following the nomenclatural conventions set out in the International Code of Area Nomenclature, Morrone (2015) defined the next biogeographic kingdoms (or realms) and regions:

  • Holarctic kingdom Heilprin (1887)
    • Nearctic region Sclater (1858)
    • Palearctic region Sclater (1858)
  • Holotropical kingdom Rapoport (1968)
    • Neotropical region Sclater (1858)
    • Ethiopian region Sclater (1858)
    • Oriental region Wallace (1876)
  • Austral kingdom Engler (1899)
    • Cape region Grisebach (1872)
    • Andean region Engler (1882)
    • Australian region Sclater (1858)
    • Antarctic region Grisebach (1872)
  • Transition zones:
    • Mexican transition zone (Nearctic–Neotropical transition)
    • Saharo-Arabian transition zone (Palearctic–Ethiopian transition)
    • Chinese transition zone (Palearctic–Oriental transition zone transition)
    • Indo-Malayan, Indonesian or Wallace's transition zone (Oriental–Australian transition)
    • South American transition zone (Neotropical–Andean transition)

Freshwater biogeographic realms

Major continental divides, showing drainage into the major oceans and seas of the world – grey areas are endorheic basins that do not drain to the ocean.

The applicability of Udvardy (1975) scheme to most freshwater taxa is unresolved (Abell et al. 2008).

The drainage basins of the principal oceans and seas of the world are marked by continental divides. The grey areas are endorheic basins that do not drain to the ocean.

Marine biogeographic realms

According to Briggs (1995) and Morrone (2009):

  • Indo-West Pacific region
  • Eastern Pacific region
  • Western Atlantic region
  • Eastern Atlantic region
  • Southern Australian region
  • Northern New Zealand region
  • Western South America region
  • Eastern South America region
  • Southern Africa region
  • Mediterranean–Atlantic region
  • Carolina region
  • California region
  • Japan region
  • Tasmanian region
  • Southern New Zealand region
  • Antipodean region
  • Subantarctic region
  • Magellan region
  • Eastern Pacific Boreal region
  • Western Atlantic Boreal region
  • Eastern Atlantic Boreal region
  • Antarctic region
  • Arctic region

According to the WWF scheme (Spalding, 2007):

See also


  • Abell, R., M. Thieme, C. Revenga, M. Bryer, M. Kottelat, N. Bogutskaya, B. Coad, N. Mandrak, S. Contreras-Balderas, W. Bussing, M. L. J. Stiassny, P. Skelton, G. R. Allen, P. Unmack, A. Naseka, R. Ng, N. Sindorf, J. Robertson, E. Armijo, J. Higgins, T. J. Heibel, E. Wikramanayake, D. Olson, H. L. Lopez, R. E. d. Reis, J. G. Lundberg, M. H. Sabaj Perez, and P. Petry. (2008). Freshwater ecoregions of the world: A new map of biogeographic units for freshwater biodiversity conservation. BioScience 58:403-414, [1].
  • "Ecozones". BBC Nature. n.d. Archived from the original on 10 July 2018.
  • Briggs, J.C. (1995). Global Biogeography. Amsterdam: Elsevier.
  • Morrone, J. J. (2009). Evolutionary biogeography, an integrative approach with case studies. Columbia University Press, New York, [2].
  • Morrone, J. J. (2015). Biogeographical regionalisation of the world: a reappraisal. Australian Systematic Botany 28: 81-90, [3].
  • 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].
  • Olson, D. M., Dinerstein, E., Wikramanayake, E. D., Burgess, N. D., Powell, G. V. N., Underwood, E. C., D'Amico, J. A., Itoua, I., Strand, H. E., Morrison, J. C., Loucks, C. J., Allnutt, T. F., Ricketts, T. H., Kura, Y., Lamoreux, J. F., Wettengel, W. W., Hedao, P., Kassem, K. R. (2001). Terrestrial ecoregions of the world: a new map of life on Earth. Bioscience 51(11):933-938, [5].
  • Schültz, J. Die Ökozonen der Erde, 1st ed., Ulmer, Stuttgart, Germany, 1988, 488 pp.; 2nd ed., 1995, 535 pp.; 3rd ed., 2002. Transl.: The Ecozones of the World: The Ecological Divisions of the Geosphere. Berlin: Springer-Verlag, 1995; 2nd ed., 2005, [6].
  • Scott, G. 1995. Canada's vegetation: a world perspective, p., [7].
  • Spalding, M. D. et al. (2007). Marine ecoregions of the world: a bioregionalization of coastal and shelf areas. BioScience 57: 573-583, [8].
  • Udvardy, M. D. F. (1975). A classification of the biogeographical provinces of the world. IUCN Occasional Paper no. 18. Morges, Switzerland: IUCN, [9].
  • Wicken, E. B. 1986. Terrestrial ecozones of Canada / Écozones terrestres du Canada. Environment Canada. Ecological Land Classification Series No. 19. Lands Directorate, Ottawa. 26 pp., [10].
Antarctic realm

The Antarctical realm is one of eight terrestrial biogeographic realms. The ecosystem includes Antarctica and several island groups in the southern Atlantic and Indian Oceans. The continent of Antarctica is so cold and dry that it has supported only 2 vascular plants for millions of years, and its flora presently consists of around 250 lichens, 100 mosses, 25-30 liverworts, and around 700 terrestrial and aquatic algal species, which live on the areas of exposed rock and soil around the shore of the continent. Antarctica's two flowering plant species, the Antarctic hair grass (Deschampsia antarctica) and Antarctic pearlwort (Colobanthus quitensis), are found on the northern and western parts of the Antarctic Peninsula. Antarctica is also home to a diversity of animal life, including penguins, seals, and whales.

Several Antarctic island groups are considered part of the Antarctica realm, including South Georgia and the South Sandwich Islands, South Orkney Islands, the South Shetland Islands, Bouvet Island, the Crozet Islands, Prince Edward Islands, Heard Island, the Kerguelen Islands, and the McDonald Islands. These islands have a somewhat milder climate than Antarctica proper, and support a greater diversity of tundra plants, although they are all too windy and cold to support trees.

Antarctic krill is the keystone species of the ecosystem of the Southern Ocean, and is an important food organism for whales, seals, leopard seals, fur seals, crabeater seals, squid, icefish, penguins, albatrosses and many other birds. The ocean there is so full of phytoplankton because around the ice continent water rises from the depths to the light flooded surface, bringing nutrients from all oceans back to the photic zone.

On August 20, 2014, scientists confirmed the existence of microorganisms living 800 metres (2,600 feet) below the ice of Antarctica.

Australasian realm

The Australasian realm is a biogeographic realm that is coincident, but not synonymous (by some definitions), with the geographical region of Australasia. The realm includes Australia, the island of New Guinea (including Papua New Guinea and the Indonesian province of Papua), and the eastern part of the Indonesian archipelago, including the island of Sulawesi, the Moluccan islands (the Indonesian provinces of Maluku and North Maluku) and islands of Lombok, Sumbawa, Sumba, Flores, and Timor, often known as the Lesser Sundas.

The Australasian realm also includes several Pacific island groups, including the Bismarck Archipelago, Vanuatu, the Solomon Islands, and New Caledonia. New Zealand and its surrounding islands are a distinctive sub-region of the Australasian realm. The rest of Indonesia is part of the Indomalayan realm.


A biome is a community of plants and animals that have common characteristics for the environment they exist in. They can be found over a range of continents. Biomes are distinct biological communities that have formed in response to a shared physical climate. Biome is a broader term than habitat; any biome can comprise a variety of habitats.

While a biome can cover large areas, a microbiome is a mix of organisms that coexist in a defined space on a much smaller scale. For example, the human microbiome is the collection of bacteria, viruses, and other microorganisms that are present on or in a human body.A 'biota' is the total collection of organisms of a geographic region or a time period, from local geographic scales and instantaneous temporal scales all the way up to whole-planet and whole-timescale spatiotemporal scales. The biotas of the Earth make up the biosphere.

Culiseta arenivaga

Culiseta arenivaga is a species of mosquito in the family Culicidae found on Fraser Island, Queensland, Australia, in the Australasian biogeographic realm. The holotype and paratype specimens were collected in 1967 by Dr. Elizabeth N. Marks who described the new species the following year.

Ecoregions of Zambia

The biomes and ecoregions in the ecology of Zambia are described, listed and mapped here, following the World Wildlife Fund's Global 200 classification scheme for terrestrial ecoregions, and the WWF freshwater bioregion classification for rivers, lakes and wetlands.

Zambia is in the Afrotropic biogeographic realm (or ecozone) of the scheme. Three terrestrial biomes are well represented in the country (with an additional one extending a few kilometres over the border).

The distribution of the biomes and ecoregions is governed mainly by the physical environment, especially climate.

Glossary of ecology

This glossary of ecology is a list of definitions of terms and topics in ecology and related fields. For more specific definitions from other glossaries related to ecology, see Glossary of biology and Glossary of environmental science.


The Holarctic is the name for the biogeographic realm that encompasses the majority of habitats found throughout the northern continents of the world, combining Wallace's Palearctic zoogeographical region, consisting of North Africa and all of Eurasia (with the exception of the southern Arabian Peninsula, Southeast Asia, and the Indian subcontinent), and the Nearctic zoogeographical region, consisting of North America, north of Mexico. These regions are further subdivided into a variety of ecoregions. Many ecosystems, and the animal and plant communities that depend on them, are found across multiple continents in large portions of this realm. The continuity of these ecosystems results from the shared glacial history of the realm. The floristic Boreal Kingdom corresponds to the Holarctic realm.

Interim Biogeographic Regionalisation for Australia

The Interim Biogeographic Regionalisation for Australia (IBRA) is a biogeographic regionalisation of Australia developed by the Australian Government's Department of Sustainability, Environment, Water, Population and Communities. It was developed for use as a planning tool, for example for the establishment of a National Reserve System.

Within the broadest scale, Australia is a major part of the Australasia biogeographic realm, as developed by the World Wide Fund for Nature. Based on this system, the world is also split into 14 terrestrial habitats of which eight are shared by Australia. The Australian land mass is divided into 89 bioregions and 419 subregions. Each region is a land area made up of a group of interacting ecosystems that are repeated in similar form across the landscape.

The most recent version is IBRA7, developed during 2012, which replaced IBRA6.1.

List of biogeographic provinces

Biogeographic Province is a biotic subdivision of realms.

The following list of biogeographic provinces was developed by Miklos Udvardy in 1975, later modified by other authors.

List of ecoregions in Bulgaria

This is a list of the various types of ecoregions in Bulgaria - Terrestrial ecoregions and Freshwater Ecoregions as defined by the World Wildlife Fund and the Marine Ecoregions of the World—MEOW global classification system. Broadly, Bulgarian nature belongs to the Palearctic terrestrial ecozone (biogeographic realm). The freshwater ecoregions in Bulgaria are examples for Temperate coastal rivers habitat (one of the twelve major types of freshwater ecoregions) and form part of the Eurafrican Mediterranean Sea Freshwater biogeographic realm. The marine ecoregion of the Black sea is classified as part of the Mediterranean–Atlantic region marine biogeographic realm according to Briggs (1995) or, alternatively, to the Temperate Northern Atlantic Marine biogeographic realm according to the WWF scheme (Spalding, 2007). Apart of being present all the 4 Marine world biomes, the terrestrial biomes that can be found in Bulgaria are: Temperate deciduous forest, Coniferous forest (Taiga in the mountains), Woodland, Tundra (Alpine tundra in the highest mountains, being Snezhnika glacier (41°46′09″) in Pirin massif the southernmost glacial mass in Europe), Chaparral or Shrubland in the south-western corner of Bulgaria., and Grassland in Dobruja, which is 6 out of the 9 world terrestrial biomes (according to the classification of the terrestrial biomes proposed by Kendeigh (1961). With a relatively limited territory of 110 993, Bulgaria presents diverse nature with great variety of biomes, habitats and ecoregions, thanks to its peninsular location, varied topography and climate, coasts and rivers. The interaction of complex climatic, hydrological, geological and topographical conditions make Bulgaria one of the most biologically diverse countries of Europe.This list may not reflect all the relevant information.

List of tree species by shade tolerance

A list of tree species, grouped generally by biogeographic realm and specifically by bioregions, and shade tolerance. Shade-tolerant species are species that are able to thrive in the shade, and in the presence of natural competition by other plants. Shade-intolerant species require full sunlight and little or no competition. Intermediate shade-tolerant trees fall somewhere in between the two.

Living Planet Index

The Living Planet Index (LPI) is an indicator of the state of global biological diversity, based on trends in vertebrate populations of species from around the world. The Zoological Society of London (ZSL) manages the index in cooperation with the World Wide Fund for Nature (WWF) a.k.a. the World Wildlife Federation.

As of 2018, the index is statistically created from journal studies, online databases and government reports for 16,704 populations of 4,005 species of mammal, bird, reptile, amphibian and fish, or approximately six percent of the world's vertebrate species.

Palearctic realm

The Palearctic or Palaearctic is one of the eight biogeographic realms on the Earth's surface, first identified in the 19th century, and is still in use as the basis for zoogeographic classification. The Palearctic is the largest of the eight realms. It stretches across all of Europe, Asia north of the foothills of the Himalayas, North Africa, and the northern and central parts of the Arabian Peninsula.

The realm consists of several ecoregions: the Euro-Siberian region; the Mediterranean Basin; the Sahara and Arabian Deserts; and Western, Central and East Asia. The Palaearctic realm also has numerous rivers and lakes, forming several freshwater ecoregions. Some of the rivers were the source of water for the earliest recorded civilizations that used irrigation methods.

Pristimantis versicolor

Pristimantis versicolor is a species of frog in the family Craugastoridae.

Red List Index

The Red List Index (RLI), based on the IUCN Red List of Threatened Species, is an indicator of the changing state of global biodiversity. It defines the conservation status of major species groups, and measures trends in extinction risk over time. By conducting conservation assessments at regular intervals, changes in the threat status of species in a taxonomic group can be used to monitor trends in extinction risk. RLIs have been calculated for birds and amphibians, using changes in threat status for species in each of the groups.

As well as taxonomic groups, RLIs can show trends in extinction risk according to biogeographic realm, habitat type, and dominant threat process.

Rhipicephalus pulchellus

Rhipicephalus pulchellus (zebra tick or yellow back tick) is a species of hard tick. It is a very common tick in the Horn of Africa, with a habitat of the Rift Valley and eastward. It hosts upon a wide variety of species, including livestock, wild mammals, and humans, and can be a vector for various pathogens. The adult male has a distinctive black and ivory ornamentation on its scutum.

Southwest Amazon moist forests

The Southwest Amazon moist forests (NT0166) is an ecoregion located in the Upper Amazon basin.

The forest is characterized by a relatively flat landscape with alluvial plains dissected by undulating hills or high terraces. The biota of the southwest Amazon moist forest is very rich because of these dramatic edaphic and topographical variations at both the local and regional levels. This ecoregion has the highest number of both mammals and birds recorded for the Amazonian biogeographic realm: 257 with 11 endemic species for mammals and 782 and 17 endemics for birds. The inaccessibility of this region, along with few roads, has kept most of the habitat intact. Also, there are a number of protected areas, which preserve this extremely biologically rich ecoregion.

Wildlife of Mauritania

Mauretania's wildlife has two main influences as the country lies in two Biogeographic realms, the north sits in the Palearctic which extends south from the Sahara to roughly 19° North and the south in the Afrotropic realms. Additionally Mauritania is important for numerous birds which migrate from the Palearctic to winter there.

Biogeographic realms
See also


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