The Palearctic or Palaearctic is one of the eight ecozones dividing the Earth's surface.
Physically, the Palearctic is the largest ecozone. It includes the terrestrial ecoregions of Europe, Asia north of the Himalaya foothills, northern Africa, and the northern and central parts of the Arabian Peninsula.
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The Palearctic ecozone includes mostly boreal and temperate climate ecoregions, which run across Eurasia from western Europe to the Bering Sea.
The boreal and temperate Euro-Siberian region is the Palearctic's largest biogeographic region, which transitions from tundra in the northern reaches of Russia and Scandinavia to the vast taiga, the boreal coniferous forests which run across the continent. South of the taiga are a belt of temperate broadleaf and mixed forests and temperate 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 the Nearctic ecoregion of North America. Eurasia and North America were often connected by the Bering land bridge, and have very similar mammal 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 single Holarctic ecozone. The Palearctic and Nearctic also share many plant species, which botanists call the Arcto-Tertiary Geoflora.
The lands bordering the Mediterranean Sea in southern Europe, north Africa, and western Asia are home to the Mediterranean basin ecoregions, which together constitute world's largest and most diverse mediterranean climate region of the world, with generally mild, rainy winters and hot, dry summers. The Mediterranean basin's mosaic of Mediterranean forests, woodlands, and scrub are home to 13,000 endemic 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, including overgrazing, deforestation, and conversion of lands for pasture, agriculture, or 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 the sclerophyll shrublands known as chaparral, matorral, maquis, or garrigue. Conservation International has designated the Mediterranean basin as one of the world's biodiversity hotspots.
A great belt of deserts, including the Atlantic coastal desert, Sahara desert, and Arabian desert, separates the Palearctic and Afrotropic ecoregions. This scheme includes these desert ecoregions in the palearctic ecozone; other biogeographers identify the ecozone 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.
The Caucasus mountains, which run between the Black Sea and the Caspian Sea, are a particularly rich mix of coniferous, broadleaf, and mixed forests, and include the temperate rain forests of the Euxine-Colchic deciduous forests ecoregion.
Central Asia and the Iranian plateau are home to dry steppe grasslands and desert 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 the Himalaya between about 2000–2500 m form the boundary between the Palearctic and Indomalaya ecoregions.
China, Korea and Japan are more humid and temperate than adjacent Siberia 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 was not much affected by glaciation in the ice ages, and retained 96 percent of Pliocene tree genera, while Europe retained only 27 percent. In the subtropical southern parts of China and, the Palearctic temperate forests transition to the subtropical and tropical forests of Indomalaya, creating a rich and diverse mix of plant and animal species. The mountains of southwest China are also designated as a biodiversity hotspot. In Southeastern Asia, high mountain ranges form tongues of Palearctic flora and fauna in northern Indochina and southern China. Isolated small outposts (sky islands) occur as far south as central Myanmar (on Nat Ma Taung, 3050 m), northernmost Vietnam (on Fan Si Pan, 3140 m) and the high mountains of Taiwan.
The ecozone contains several important freshwater ecoregions as well, including the heavily developed rivers of Europe, the rivers of Russia, which flow into the Arctic, Baltic, Black, and Caspian seas, Siberia's Lake Baikal, the oldest and deepest lake on the planet, and Japan's ancient Lake Biwa.
One bird family, the accentors (Prunellidae) is endemic to the Palearctic region. The Holarctic has four other endemic bird families: the divers or loons (Gaviidae), grouse (Tetraoninae), auks (Alcidae), and waxwings (Bombycillidae).
There are no endemic mammal 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 during the ice ages, including the Brown Bear (Ursus arctos, known in North America as the Grizzly), Red Deer (Cervus elaphus) in Europe and the closely related Elk (Cervus canadensis) in far eastern Siberia, American Bison (Bison bison), and Reindeer (Rangifer tarandus, known in North America as the Caribou).
| Guizhou Plateau broadleaf and mixed forests | China |
| Yunnan Plateau subtropical evergreen forests | China |
| East Siberian taiga | Russia |
| Iceland boreal birch forests and alpine tundra | Iceland |
| Kamchatka-Kurile meadows and sparse forests | Russia |
| Kamchatka-Kurile taiga | Russia |
| Northeast Siberian taiguhh | Russia |
| Okhotsk-Manchurian taiga | Russia |
| Sakhalin Island taiga | Russia |
| Scandinavian and Russian taiga | Finland, Norway, Russia, Sweden |
| Trans-Baikal conifer forests | Mongolia, Russia |
| Urals montane tundra and taiga | Russia |
| West Siberian taiga | Russia |
| Puszcza Romnicka | Poland, Russia |
| Alai-Western Tian Shan steppe | Kazakhstan, Tajikistan, Uzbekistan |
| Altai steppe and semi-desert | Kazakhstan |
| Central Anatolian steppe | Turkey |
| Daurian forest steppe | China, Mongolia, Russia |
| Eastern Anatolian montane steppe | Armenia, Iran, Turkey |
| Emin Valley steppe | China, Kazakhstan |
| Faroe Islands boreal grasslands | Faroe Islands, Denmark |
| Gissaro-Alai open woodlands | Kyrgyzstan, Tajikistan, Uzbekistan |
| Kazakh forest steppe | Kazakhstan, Russia |
| Kazakh steppe | Kazakhstan, Russia |
| Kazakh upland | Kazakhstan |
| Middle East steppe | Iraq, Syria |
| Mongolian-Manchurian grassland | China, Mongolia, Russia |
| Pontic steppe | Kazakhstan, Moldova, Romania, Russia, Ukraine |
| Sayan Intermontane steppe | Russia |
| Selenge-Orkhon forest steppe | Mongolia, Russia |
| South Siberian forest steppe | Russia |
| Tian Shan foothill arid steppe | China, Kazakhstan, Kyrgyzstan |
| Amur meadow steppe | China, Russia |
| Bohai Sea saline meadow | China |
| Nenjiang River grassland | China |
| Nile Delta flooded savanna | Egypt |
| Saharan halophytics | Algeria, Egypt, Mauritania, Tunisia, Western Sahara |
| Tigris-Euphrates alluvial salt marsh | Iraq, Iran |
| Ussuri-Wusuli meadow and forest meadow | China, Russia |
| Yellow Sea saline meadow | China |
| Altai alpine meadow and tundra | China, Kazakhstan, Mongolia, Russia |
| Central Tibetan Plateau alpine steppe | China |
| Eastern Himalayan alpine shrub and meadows | Bhutan, Burma, China, India, Nepal |
| Ghorat-Hazarajat alpine meadow | Afghanistan |
| Hindu Kush alpine meadow | Afghanistan, Pakistan |
| Karakoram-West Tibetan Plateau alpine steppe | Afghanistan, China, India, Pakistan |
| Khangai Mountains alpine meadow | Mongolia |
| Kopet Dag woodlands and forest steppe | Iran, Turkmenistan |
| Kuhrud-Kohbanan Mountains forest steppe | Iran |
| Mediterranean High Atlas juniper steppe | Morocco |
| North Tibetan Plateau-Kunlun Mountains alpine desert | China |
| Northwestern Himalayan alpine shrub and meadows | China, India, Pakistan |
| Ordos Plateau steppe | China |
| Pamir alpine desert and tundra | Afghanistan, China, Kyrgyzstan, Tajikistan |
| Qilian Mountains subalpine meadows | China |
| Sayan Alpine meadows and tundra | Mongolia, Russia |
| Southeast Tibet shrub and meadows | China |
| Sulaiman Range alpine meadows | Afghanistan, Pakistan |
| Tian Shan montane steppe and meadows | China, Kazakhstan, Kyrgyzstan |
| Tibetan Plateau alpine shrub and meadows | China |
| Western Himalayan alpine shrub and meadows | India, Nepal |
| Yarlung Zambo arid steppe | China |
| Arctic desert | Russia, Svalbard (Norway) |
| Bering tundra | Russia |
| Cherskii-Kolyma mountain tundra | Russia |
| Chukchi Peninsula tundra | Russia |
| Kamchatka Mountain tundra and forest tundra | Russia |
| Kola Peninsula tundra | Norway, Russia |
| Northeast Siberian coastal tundra | Russia |
| Northwest Russian-Novaya Zemlya tundra | Russia |
| Novosibirsk Islands arctic desert | Russia |
| Scandinavian Montane Birch forest and grasslands | Finland, Norway, Sweden |
| Taimyr-Central Siberian tundra | Russia |
| Trans-Baikal Bald Mountain tundra | Russia |
| Wrangel Island arctic desert | Russia |
| Yamalagydanskaja tundra | Russia |
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