Nearctic

Nearctic is one of the eight biogeographic realms used in the study of global biodiversity. It encompasses most of North America north of the Isthmus of Tehuantepec, including Greenland, and is often considered part of the larger Holarctic region when paired with the Palearctic.

Boundaries and extent: The southern boundary with the Neotropical realm runs roughly along southern Mexico. The realm extends north to the Arctic Ocean and includes a wide range of climates and environments, from Arctic tundra and boreal forests to temperate deciduous forests, grasslands, and arid deserts. The western boundary is defined by the Pacific, and the eastern boundary by the Atlantic and Gulf of Mexico regions.

Habitats and climate: The Nearctic hosts a diversity of biomes, including tundra in the far north, taiga and mixed conifer forests across Canada and Alaska, temperate forests in the eastern half of North America, the Great Plains grasslands, and desert regions in the southwestern United States and northern Mexico. This range reflects historical glaciations and subsequent recolonization patterns.

Flora and fauna: The realm features coniferous and broadleaf trees, prairie grasses, and a variety of shrubs and herbs. Its fauna includes species such as the American bison, grizzly and black bears, moose, elk, mule deer, pronghorn, beaver, and numerous rodents. Birds of national and international prominence, such as the bald eagle and various waterfowl, are characteristic. Many lineages are shared with the Palearctic, while others are endemic or concentrate in refugial areas created by past climatic changes.

Etymology and significance: The name Nearctic derives from Latin for “near Arctic,” reflecting its northern position. The concept is central to biogeography for comparing regional assemblages and studying disjunct distributions within the Holarctic.