In an 1858 paper for theProceedings of theLinnean Society, British zoologistPhilip Sclater first 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 Wallace adopted 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:Oceania and theAntarctic.
The boreal and temperate Euro-Siberian region is the Palearctic's largestbiogeographic region, which transitions fromtundra in the northern reaches ofRussia andScandinavia to the vasttaiga, the boreal coniferous forests which run across the continent. South of the taiga is a belt oftemperate broadleaf and mixed forests andtemperate 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 realm ofNorth America. Eurasia and North America were often connected by theBering land bridge, and have very similarmammal and 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.
The lands bordering theMediterranean Sea in southern Europe, north Africa, and western Asia are home to theMediterranean Basin ecoregions, which together constitute the world's largest and most diversemediterranean climate region of the world, with generally mild, rainy winters and hot, dry summers. The Mediterranean basin's mosaic ofMediterranean forests, woodlands, and scrub are home to 13,000endemic species. 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 thesclerophyll shrublands known aschaparral,matorral,maquis, orgarrigue.Conservation International has designated the Mediterranean basin as one of the world'sbiodiversity hotspots.
A great belt of deserts, including theAtlantic coastal desert,Sahara Desert, andArabian Desert, separates the Palearctic andAfrotropic ecoregions. 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.
Central Asia and theIranian plateau are home to drysteppegrasslands anddesert basins, 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 theHimalaya between about 2,000–2,500 m (6,600–8,200 ft) form the boundary between the Palearctic andIndomalaya ecoregions.
China,Korea andJapan are more humid and temperate than adjacentSiberia and 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's temperate forests are rich in biodiversity, with 185 tree genera compared to 53 in Europe and 99 in Eastern North America. East Asia lost fewer tree genera during the ice ages than other temperate forest regions, and retained 96 percent of the tree genera in thePliocene fossil record while Europe retained only 27 percent.[2] 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 China are also designated as abiodiversity hotspot. In Southeastern Asia, highmountain ranges form tongues of Palearctic flora and fauna in northernIndochina and 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.
One bird family, theaccentors (Prunellidae), is endemic to the Palearctic region. TheHolarctic has four other endemic bird families: the divers orloons (Gaviidae),grouse (Tetraoninae),auks (Alcidae), andwaxwings (Bombycillidae).
There are no endemicmammal orders 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).
The outlined ecoregions of the eastern Palearctic realm, each of a colored biomeThe outlined ecoregions of the western Palearctic realm, each of a colored biome. Note that this realm, as a whole, has 10 of14 biomes, or major habitat types, as defined by Olson & Dinerstein, et al. (2001).[3]
^Latham, R.E. & Ricklefs, R.E. (1993a). Continental comparison of temperate-zone tree species richness. In:Species Diversity in Ecological Communities: Historical and Geographical Perspectives (eds Ricklefs, R.E. & Schluter, D.). The University of Chicago Press, Chicago, pp. 294–314.
^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,[1]Archived 2012-09-17 at theWayback Machine.
^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[2]
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 Archaeologica 61: pp. 252–271. 1991.
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.
