Nearctic realm
The Nearctic realm is one of eight major biogeographic regions that shape Earth’s lands. It covers most of North America, Greenland, and parts of northern and central Mexico. It does not include most of coastal southern Mexico, Central America, Bermuda, or the Caribbean.
Four bioregions (biogeographic clusters) in the Nearctic
- Canadian Shield
- Covers the northern part of the continent, with arctic tundra and boreal forests.
- Part of the circumboreal floristic region.
- Eastern North America
- Temperate broadleaf and mixed forests of the eastern United States and southeastern Canada.
- Also includes the Great Plains temperate grasslands and parts of southeastern U.S. conifer forests; central Florida is included.
- Represented in floristic terms by the North American Atlantic Region and part of the circumboreal region.
- Western North America
- Temperate conifer forests along the Pacific coast and in the mountains (the Cascades and beyond).
- Includes cold-winter intermountain deserts and temperate grasslands/shrublands of the western U.S.
- Represented by the Rocky Mountain region floristically.
- Northern Mexico
- Deserts and xeric shrublands; pine–oak forests; subtropical dry forests of the Mexican Plateau, Baja California, and nearby areas.
- Includes the Sonoran–Sinaloan subtropical dry forest.
- Floristically linked to the Madrean Region.
Big picture about movement and connections
- North America and South America were separated for about 180 million years after Pangaea split; they later joined and then separated again in different ways.
- After Pangaea split, North America stayed with Eurasia for a long time (Laurasia), while South America was with Gondwana. Later, land bridges allowed exchanges of plants and animals (the Great American Interchange).
- A land bridge across the Bering Strait connected Asia and North America, helping species move between continents. The Nearctic shares many plants and animals with the Palearctic (Eurasia and North Africa); sometimes the Nearctic and Palearctic are treated together as the Holarctic.
Extinctions and endemics
- At the end of the Pleistocene, many large animals in North America went extinct in what’s called the Quaternary extinction event.
- Endemic mammals (found only in the Nearctic) include the pronghorn and the mountain beaver.
- Endemic bird families in the Holarctic include divers, grouse, auks, and waxwings.
- Endemic scarab beetle families include Pleocomidae and Diphyllostomatidae.
- Plant groups endemic or nearly endemic to the Nearctic include Crossosomataceae, Simmondsiaceae, and Limnanthaceae.
This page was last edited on 3 February 2026, at 04:50 (CET).