The Palearctic or Palaearctic is one of Earth’s eight ecozones. This region is the largest ecozone on Earth. It includes the regions of Europe, Asia (north of the Himalayan foothills), northern Africa, and the northern and central regions of the Arabian Peninsula. The Palearctic includes mostly boreal forest and temperate climate regions, which are found throughout Eurasia from western Europe to the Bering Sea. There are five sub-regions of the Palearctic: European-Siberian, Mediterranean Basin, Sahara and Arabian deserts, Western and Central Asia, and China and Japan.
The European-Siberian region is the largest biogeographic region of the Palearctic. It encompasses an area from the tundra in the northern reaches of Russia and Scandinavia to the immense taiga (boreal coniferous evergreen forests that run across the land). South of the taiga are a band of temperate broadleaf, mixed, and coniferous forests. This vast region is distinguished by its numerous shared flora and fauna species. This region also resembles the temperate and boreal regions of the Nearctic ecozone of North America. The Bering land bridge once connected Eurasia to North America and many mammal and bird species are common to both areas. Many more Eurasian animal species dispersed to North America than did animals from North America move to Eurasia.
The Mediterranean Basin includes lands bordering the Mediterranean Sea in southern Europe, north Africa, and western Asia. This is the most diverse climate region found in the whole world, with mostly mild and rainy winters, and hot, dry summers. The Mediterranean forests, woodlands, and scrublands of this region are home to around 13,000 endemic species. The Mediterranean Basin is one of the world’s most endangered regions (only 4% of the region’s original plant species remains). Human activities including overgrazing, deforestation, and land conversion to pastures and urbanization, have degraded much of this region. Once covered with forests and woodlands, the Mediterranean Basin is now mostly reduced to shrublands known as chaparral, matorral, maquis, or garrigue.
The vast area of the Sahara and Arabian Desertsdeserts includes the Atlantic coastal desert, Sahara Desert, and Arabian Desert. These deserts separate the Palearctic ecozone from the Afrotropic ecozone. There is debate over the exact line of the boundary between the two ecozones. Some biogeographers place the desert ecoregion as a transition area between the Palearctic and Afrotropic ecozones, while others place the boundary right through the middle of the deserts.
The Western and Central Asia region includes the Caucasus Mountains, which lie between the Black Sea and the Caspian Sea. This area is a rich mixture of coniferous, broadleaf, and mixed forests that include the temperate rainforests of the Euxine-Colchic deciduous forests ecoregion. Central Asia and the Iranian Plateau are home to mountain forests, woodlands, grasslands, dry steppe grasslands, and desert basins. To the south, the Palearctic borders the Indomalaya ecozone in the middle of the Himalayan foothills at around 6500 – 8000 feet above sea level.
China and Japan are more humid and temperate than Siberia and Central Asia, which are adjacent to them. Rich temperate coniferous, broadleaf, and mixed forests that once covered much of China and Japan, are now mostly limited to the mountainous areas, due to heavy population of the lowlands and river basins that have been converted for agricultural and urban use. Eastern Asia was not affected as greatly by glaciation during the ice ages and retained nearly all of its Pliocene tree families. In the southern subtropical regions of China and Japan, the Palearctic temperate forests converge into the subtropical and tropical forests of Indomalaya. The mountains of southwest China are considered a biodiversity hotspot.
The Palearctic ecozone contains several freshwater ecoregions as well, including the rivers of Europe and Russia, which flow into the Arctic, Baltic, Black, and Caspian Seas. Siberia’s Lake Baikal is the oldest and deepest lake in the world. Another important freshwater region is Japan’s ancient Lake Biwa.
The fauna of the Palearctic includes one endemic bird family (Prunellidae) and four other bird families (loons, grouse, auks, waxwings) that are also endemic to the Nearctic, which together with the Palearctic is sometimes referred to as the Holarctic ecozone. There are no endemic mammal orders of this region, but some mammal families are endemic (e.g. hamsters and pandas). Many species of mammals have spread out to the Nearctic during the ice ages across the Bering land bridge. These include the Brown Bear (Grizzly), Red Deer, Elk, Bison, and Reindeer (Caribou).