Overview

The Holarctic is a biogeographic realm that groups the major terrestrial regions of the Northern Hemisphere on the basis of shared climate, vegetation and evolutionary history. It unites a wide belt of habitats across the northern continents and emphasizes ecological continuity rather than political borders. For a general introduction see Holarctic overview. The realm includes a diversity of habitats and is broadly coterminous with the northern continents or landmasses often referred to in paleogeography as the northern continents.

Major subdivisions

Conventionally the Holarctic is divided into two principal regions. The Palearctic comprises Europe, northern Africa and most of Eurasia, excluding much of South and Southeast Asia. The Nearctic covers most of North America, generally north of the transitional southern margin near southern Mexico. Each region contains numerous recognized ecoregions characterized by specific climate regimes, soils and dominant vegetation types.

Climate and habitats

The Holarctic encompasses climates from Arctic polar zones and alpine tundra through boreal (taiga) forests to temperate broadleaf forests and grasslands or steppe. Representative ecosystems include the circumpolar boreal forest, high-latitude tundra, temperate deciduous woodlands, prairie and temperate steppe. These systems show parallel patterns of seasonality, productivity and successional dynamics across continents.

Flora, fauna and biotic exchange

Many plant and animal groups are widespread across the Holarctic. Boreal conifers, temperate deciduous trees and a range of herbaceous plants form the floral backbone. Typical animal elements include large mammals such as bears, wolves, moose and deer in the mammal assemblages, migratory birds that cross continents, and numerous insect and freshwater taxa. Holarctic fauna show both widespread species and regional endemics, reflecting past connections and periods of isolation. Exchanges between Eurasia and North America, particularly across the area of the present-day Bering Strait, have been important in assembling these communities and are well documented in paleontological and genetic studies involving Asia and North American lineages.

Historical processes

The similarity of many Holarctic ecosystems derives from repeated glacial cycles in the Quaternary. During glacial maxima sea levels dropped and climatic zones shifted, creating corridors for range shifts and intercontinental dispersal. The presence of refugia, postglacial recolonization routes and intermittent land connections allowed biotic mixing and also produced patterns of vicariance and endemism. These historical processes are central to understanding modern distributions and are the subject of research in biogeography and paleobiology.

Conservation and human impacts

The Holarctic contains extensive natural resources and provides important ecosystem services, including carbon storage in boreal peatlands, freshwater provisioning from northern rivers, and fisheries in adjacent seas. Human activities—land conversion, resource extraction, climate change and invasive species—pose threats across many Holarctic ecoregions. Conservation responses commonly operate at ecoregion and transboundary scales, using protected areas, landscape connectivity planning and international cooperation to address threats. Regional inventories and management frameworks often draw on ecoregion assessments and ecosystem-level monitoring; further background is available in general summaries of Holarctic ecology and regional accounts of the Palearctic and Nearctic.

Research directions and summary

Current research in the Holarctic focuses on responses to rapid climate warming, alterations to fire and permafrost regimes, species range shifts and the genetic consequences of past and ongoing range change. Long-term datasets, paleontological records and comparative studies across the Palearctic and Nearctic are valuable for disentangling natural variability from anthropogenic change. Concise regional overviews and ecoregion lists help planners and researchers prioritize conservation actions; see linked resources on habitats, North America biogeography and Asia comparative studies for further reading.

  • Extent: Northern parts of Eurasia, North Africa and North America, treated as the Palearctic and Nearctic.
  • Key drivers: Glacial history, continental climate patterns and past land connections across the Bering region.
  • Conservation focus: Protecting large, connected landscapes and managing climate impacts on boreal and Arctic systems.

For introductory maps and curated lists of characteristic habitats and species, consult ecoregion compilations and specialist literature; useful starting points include regional portals and overviews of Holarctic ecology, detailed ecoregion listings and technical notes on northern ecosystems.