Palaearctische

Palaearctische, also known as the Palearctic region, is one of the eight biogeographic realms used in modern zoogeography to classify the geographic distribution of organisms. It spans Europe, North Africa north of the Sahara, and most of Asia north of the Himalayas, including Siberia and Central Asia, extending to the Arctic Ocean. The realm covers roughly 50 million square kilometers, making it the largest realm by land area. It is commonly divided into Western Palearctic (Europe, the Maghreb and the Middle East) and Eastern Palearctic (Siberia, Central Asia, northern China and Japan).

Its northern boundary is the Arctic, while the southern boundary follows the Sahara and Sahel, separating it from the Ethiopian realm. The eastern boundary with the Oriental realm runs through the Himalayas and western Hindu Kush, and the boundary with the Nearctic lies across the Bering Strait. The precise limits vary in taxonomic treatments, but the general concept remains consistent.

Climatically, the Palearctische encompasses tundra, boreal forest (taiga), temperate deciduous and coniferous forests, steppes of Central Asia, deserts of Central Asia and the Middle East, and Mediterranean-type ecosystems around the western and southern margins. The fauna and flora are shaped by glacial–interglacial history, with widespread temperate taxa and many northern endemics in the boreal and Mediterranean zones. The realm is distinguished by strong affinities among its western and eastern parts and by historical exchanges with the Nearctic and Oriental regions.

The term Palearctic was introduced in 19th-century biogeography as part of a system of realms developed by Sclater and later refined by Wallace to describe broad patterns of distribution.