Editing Palearctic realm (section)

==Major ecological regions==

The Palearctic realm includes mostly [[subarctic climate|boreal/subarctic-climate]] and [[temperate climate|temperate-climate]] ecoregions, which stretch from western Europe to the [[Bering Sea]].

===Euro-Siberian region===

The boreal and temperate Euro-Siberian region is the Palearctic's largest [[biogeography|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 is a belt of [[temperate broadleaf and mixed forests]] and [[temperate coniferous forest]]s. 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 realm]] 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 realm]]. The Palearctic and Nearctic also share many plant species, which botanists call the [[Arcto-Tertiary Geoflora]].

===Mediterranean Basin===
{{main|Mediterranean Basin}}
The lands bordering the [[Mediterranean Sea]] in southern Europe, north Africa, and western Asia are home to the [[Mediterranean Basin]] ecoregions, which together constitute the 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 (ecology)|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, 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 the [[sclerophyll]] shrublands known as [[chaparral]], [[matorral]], [[Maquis shrubland|maquis]], or [[garrigue]]. [[Conservation International]] has designated the Mediterranean basin as one of the world's [[biodiversity hotspot]]s.

===Sahara and Arabian deserts===
[[Horse latitudes|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 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===
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 forest]]s 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 {{Convert|2000–2500|m|abbr=on}} form the boundary between the Palearctic and [[Indomalaya]] ecoregions.

===East Asia===
[[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 age]]s, and retained 96 percent of [[Pliocene]]{{citation needed|date=August 2014}} 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 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 range]]s form tongues of Palearctic flora and fauna in northern [[Indochina]] and southern [[China]]. Isolated small outposts ([[sky island]]s) occur as far south as central Myanmar (on [[Nat Ma Taung]], {{Convert|3050|m|abbr=on|disp=semicolon}}), northernmost [[Vietnam]] (on [[Fan Si Pan]], {{Convert|3140|m|abbr=on|disp=semicolon}}) and the high mountains of [[Taiwan]].

===Freshwater===
The realm contains several important [[freshwater ecoregion]]s as well, including the heavily developed [[rivers of Europe]], the [[rivers of Russia]], which flow into the [[Arctic]], [[Baltic Sea|Baltic]], [[Black Sea|Black]], and [[Caspian Sea|Caspian]] seas, [[Siberia]]'s [[Lake Baikal]], the oldest and deepest lake on the planet, and Japan's ancient [[Lake Biwa]].