Palearctic realm
 | This article includes a list of generalreferences,butit lacks sufficient correspondinginline citations.(May 2015) |
ThePalearcticorPalaearcticis the largest of the eightbiogeographic realmsof the Earth. It stretches across all ofEurasianorth of the foothills of theHimalayas,andNorth Africa.
The realm consists of severalbioregions:the Euro-Siberian region; theMediterranean Basin;theSaharaandArabian Deserts;andWestern,CentralandEast Asia.The Palaearctic realm also has numerous rivers and lakes, forming several freshwater ecoregions.
The term 'Palearctic' was first used in the 19th century, and is still in use as the basis forzoogeographicclassification.
History[edit]
In an 1858 paper for theProceedings of theLinnean Society,British zoologistPhilip Sclaterfirst identified six terrestrial zoogeographic realms of the world: Palaearctic, Aethiopian/Afrotropic,Indian/Indomalayan,Australasian,Nearctic,andNeotropical.The six indicated general groupings of fauna, based on shared biogeography and large-scale geographic barriers to migration.[1]
Alfred Wallaceadopted Sclater's scheme for his bookThe Geographical Distribution of Animals,published in 1876. This is the same scheme that persists today, with relatively minor revisions, and the addition of two more realms:Oceaniaand theAntarctic realm.
Major ecological regions[edit]
The Palearctic realm includes mostlyboreal/subarctic-climateandtemperate-climateecoregions, which run acrossEurasiafrom western Europe to theBering Sea.
Euro-Siberian region[edit]
The boreal and temperate Euro-Siberian region is the Palearctic's largestbiogeographicregion, which transitions fromtundrain the northern reaches ofRussiaandScandinaviato the vasttaiga,the boreal coniferous forests which run across the continent. South of the taiga are a belt oftemperate broadleaf and mixed forestsandtemperate coniferous forests.This vast Euro-Siberian region is characterized by many shared plant and animal species, and has many affinities with the temperate and boreal regions of theNearctic realmofNorth America.Eurasia and North America were often connected by theBering land bridge,and have very similarmammaland bird fauna, with many Eurasian species having moved into North America, and fewer North American species having moved into Eurasia. Many zoologists consider the Palearctic and Nearctic to be a singleHolarctic realm.The Palearctic and Nearctic also share many plant species, which botanists call theArcto-Tertiary Geoflora.
Mediterranean Basin[edit]
The lands bordering theMediterranean Seain southern Europe, north Africa, and western Asia are home to theMediterranean Basinecoregions, which together constitute the world's largest and most diversemediterranean climateregion of the world, with generally mild, rainy winters and hot, dry summers. The Mediterranean basin's mosaic ofMediterranean forests, woodlands, and scrubare home to 13,000endemicspecies. The Mediterranean basin is also one of the world's most endangered biogeographic regions; only 4% of the region's original vegetation remains, and human activities, includingovergrazing,deforestation,and conversion of lands for pasture, agriculture, and urbanization, have degraded much of the region. Formerly the region was mostly covered with forests and woodlands, but heavy human use has reduced much of the region to thesclerophyllshrublands known aschaparral,matorral,maquis,orgarrigue.Conservation Internationalhas designated the Mediterranean basin as one of the world'sbiodiversity hotspots.
Sahara and Arabian deserts[edit]
A great belt of deserts,including theAtlantic coastal desert,Saharadesert, andArabian desert,separates the Palearctic andAfrotropicecoregions. This scheme includes these desert ecoregions in the palearctic realm; other biogeographers identify the realm boundary as the transition zone between the desert ecoregions and the Mediterranean basin ecoregions to the north, which places the deserts in the Afrotropic, while others place the boundary through the middle of the desert.
Western and Central Asia[edit]
TheCaucasusmountains, which run between theBlack Seaand theCaspian Sea,are a particularly rich mix of coniferous, broadleaf, and mixed forests, and include thetemperate rain forestsof theEuxine-Colchic deciduous forestsecoregion.
Central Asiaand theIranian plateauare home to drysteppegrasslandsanddesertbasins, with montane forests, woodlands, and grasslands in the region's high mountains and plateaux. In southern Asia the boundary of the Palearctic is largely altitudinal. The middle altitude foothills of theHimalayabetween about 2,000–2,500 m (6,600–8,200 ft) form the boundary between the Palearctic andIndomalayaecoregions.
East Asia[edit]
China,KoreaandJapanare more humid and temperate than adjacentSiberiaand Central Asia, and are home to rich temperate coniferous, broadleaf, and mixed forests, which are now mostly limited to mountainous areas, as the densely populated lowlands and river basins have been converted to intensive agricultural and urban use. East Asia was not much affected by glaciation in theice ages,and retained 96 percent ofPliocene[citation needed]tree genera, while Europe retained only 27 percent. In the subtropical region of southern China and southern edge of the Himalayas, the Palearctic temperate forests transition to the subtropical and tropical forests ofIndomalaya,creating a rich and diverse mix of plant and animal species. Themountains of southwest Chinaare also designated as abiodiversity hotspot.In Southeastern Asia, highmountain rangesform tongues of Palearctic flora and fauna in northernIndochinaand southernChina.Isolated small outposts (sky islands) occur as far south as central Myanmar (onNat Ma Taung,3,050 m; 10,010 ft), northernmostVietnam(onFan Si Pan,3,140 m; 10,300 ft) and the high mountains ofTaiwan.
Freshwater[edit]
The realm contains several importantfreshwater ecoregionsas well, including the heavily developedrivers of Europe,therivers of Russia,which flow into theArctic,Baltic,Black,andCaspianseas,Siberia'sLake Baikal,the oldest and deepest lake on the planet, and Japan's ancientLake Biwa.
Flora and fauna[edit]
One bird family, theaccentors(Prunellidae), is endemic to the Palearctic region. TheHolarctichas four other endemic bird families: the divers orloons(Gaviidae),grouse(Tetraoninae),auks(Alcidae), andwaxwings(Bombycillidae).
There are no endemicmammalorders in the region, but several families are endemic: Calomyscidae (mouse-like hamsters),Prolagidae,and Ailuridae (red pandas). Several mammal species originated in the Palearctic and spread to the Nearctic duringthe Ice Age,including thebrown bear(Ursus arctos,known in North America as the grizzly),red deer(Cervus elaphus) in Europe and the closely relatedelk(Cervus canadensis) in far eastern Siberia,American bison(Bison bison), andreindeer(Rangifer tarandus,known in North America as thecaribou).
Megafaunal extinctions[edit]
Several large Palearctic animals became extinct from the end of thePleistoceneinto historic times, includingIrish elk(Megaloceros giganteus),aurochs(Bos primigenius),woolly rhinoceros(Coelodonta antiquitatis),woolly mammoth(Mammuthus primigenius),North African elephant(Loxodonta africana pharaoensis),Chinese elephant(Elephas maximus rubridens),cave bear(Ursus spelaeus),Straight tusked elephant(Palaeoloxodon antiquus) andEuropean lion(Panthera leo europaea).
Palearctic terrestrial ecoregions[edit]
| Guizhou Plateau broadleaf and mixed forests | China |
| Yunnan Plateau subtropical evergreen forests | China |
References[edit]
- ^Sclater, Philip Lutley(1858)."On the general geographical distribution of the members of the class Aves".Zoological Journal of the Linnean Society.2(7): 130–145.doi:10.1111/j.1096-3642.1858.tb02549.x.
- ^Eric Dinerstein, David Olson, et al. (2017). An Ecoregion-Based Approach to Protecting Half the Terrestrial Realm, BioScience, Volume 67, Issue 6, June 2017, Pages 534–545[1]
General references[edit]
- Amorosi, T. "Contributions to the zooarchaeology of Iceland: some preliminary notes" inThe Anthropology of Iceland(eds. E.P. Durrenberger & G. Pálsson). Iowa City:University of Iowa Press,pp. 203–227, 1989.
- Buckland, P.C., et al. "Holt in Eyjafjasveit, Iceland: a paleoecological study of the impact of Landnám" inActa Archaeologica61: pp. 252–271. 1991.
- http:// Merriam-Webster
- http:// Canadianbiodiversity.mcgill.ca
- http:// bbc.co.uk/nature/ecozones/Palearctic_ecozone
- Edmund Burke III, "The Transformation of the middle Eastern Environment, 1500 B.C.E.–2000 C.E." inThe Environment and World History,ed. Edmund Burke III and Kenneth Pomeranz. Berkeley: University of California Press. 2009, 82–84.
External links[edit]
Mediafrom Commons
Travel informationfrom Wikivoyage
- Avionary1500 Bird species of the Western and Central Palaearctic in 46 languages
- Map of the ecozones
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