The Nearctic realm is one of the eight
biogeographic realms constituting the Earth's land surface.
The Nearctic realm covers most of
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, including
Greenland
Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...
,
Central Florida
Central Florida is a Regions of the United States#Florida, region of the U.S. state of Florida. Different sources give different definitions for the region, but as its name implies it is usually said to comprise the central part of the state, in ...
, and the highlands of
Mexico
Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
. The parts of North America that are not in the Nearctic realm include most of coastal Mexico, southern Mexico,
southern Florida, coastal central
Florida
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
,
Central America
Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually ...
,
Bermuda
Bermuda is a British Overseas Territories, British Overseas Territory in the Atlantic Ocean, North Atlantic Ocean. The closest land outside the territory is in the American state of North Carolina, about to the west-northwest.
Bermuda is an ...
and the
Caribbean
The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...
islands. Together with
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
, these regions are part of the
Neotropical realm
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropics, tropical Ecoregion#Terrestrial, terrestrial ecoregions of the Americas and the entire South American temperat ...
.
Major ecological regions
The
World Wildlife Fund (WWF) divides the Nearctic into four
bioregions, defined as "geographic clusters of ecoregions that may span several habitat types, but have strong biogeographic affinities, particularly at taxonomic levels higher than the species level (genus, family)."
Canadian Shield
The
Canadian Shield bioregion extends across the northern portion of the continent, from the
Aleutian Islands to
Newfoundland. It includes the Nearctic's
arctic tundra and
boreal forest ecoregions.
In terms of
floristic provinces, it is represented by part of the Canadian Province of the
Circumboreal Region.
Eastern North America
The Eastern North America bioregion includes the
temperate broadleaf and mixed forests of the Eastern United States and southeastern Canada, the
Great Plains
The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...
temperate grasslands of the central United States and south-central Canada, the
temperate coniferous forests of the southeastern United States, including
central Florida
Central Florida is a Regions of the United States#Florida, region of the U.S. state of Florida. Different sources give different definitions for the region, but as its name implies it is usually said to comprise the central part of the state, in ...
. In terms of
floristic provinces, it is represented by the
North American Atlantic Region and part of the Canadian Province of the
Circumboreal Region.
Western North America
The Western North America bioregion includes the
temperate coniferous forests of the coastal and mountain regions of southern Alaska, western Canada, and the western United States from the
Pacific Coast and
Northern California
Northern California (commonly shortened to NorCal) is a geocultural region that comprises the northern portion of the U.S. state of California, spanning the northernmost 48 of the state's List of counties in California, 58 counties. Northern Ca ...
to the
Rocky Mountains (known as the
Cascadian bioregion), as well as the cold-winter intermountain
deserts and xeric shrublands
Deserts and xeric shrublands are a biome defined by the World Wide Fund for Nature. Deserts and xeric (Ancient Greek 'dry') shrublands form the largest terrestrial biome, covering 19% of Earth's land surface area. Ecoregions in this habitat ...
and temperate grasslands and shrublands of the
Western United States.
In terms of
floristic provinces, it is represented by the
Rocky Mountain region.
Northern Mexico
The Northern Mexico bioregion includes the mild-winter to cold-winter deserts and xeric shrublands, warm temperate and subtropical pine and
pine-oak forests, and Mediterranean climate ecoregions of the
Mexican Plateau,
Baja California peninsula, and the
southwestern United States, bordered to the south by the
Neotropical Trans-Mexican Volcanic Belt. This region also includes the only
subtropical dry broadleaf forest in the Nearctic realm, the
Sonoran–Sinaloan transition subtropical dry forest.
In terms of
floristic provinces, it is represented by the
Madrean Region.
History
Although North America and South America are presently joined by the
Isthmus of Panama, these continents were separated for about 180 million years, and evolved very different plant and animal lineages. When the ancient supercontinent of
Pangaea split into two about 180 million years ago, North America remained joined to
Eurasia
Eurasia ( , ) is a continental area on Earth, comprising all of Europe and Asia. According to some geographers, Physical geography, physiographically, Eurasia is a single supercontinent. The concept of Europe and Asia as distinct continents d ...
as part of the supercontinent of
Laurasia, while South America was part of the supercontinent of
Gondwana. North America later split from Eurasia. North America has been joined by land bridges to both
Asia
Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
and South America since then, which allowed an exchange of plant and animal
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
between the continents, the
Great American Interchange.
A former land bridge across the
Bering Strait between Asia and North America allowed many plants and animals to move between these continents, and the Nearctic realm shares many plants and animals with the
Palearctic
The Palearctic or Palaearctic is a biogeographic realm of the Earth, the largest of eight. Confined almost entirely to the Eastern Hemisphere, it stretches across Europe and Asia, north of the foothills of the Himalayas, and North Africa.
Th ...
. The two realms are sometimes included in a single
Holarctic realm.
Many large animals, or
megafauna, including
horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...
s,
camels,
tapirs,
mammoths,
mastodons,
ground sloths, sabre-tooth cats (''
Smilodon''),
short-faced bears and the
American cheetah, became extinct in North America at the end of the
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
epoch (ice ages) in what is called the
Quaternary extinction event.
Flora and fauna
Flora and fauna that originated in the Nearctic
Mammals originally unique to the Nearctic include:
* Order
Primate
Primates is an order (biology), order of mammals, which is further divided into the Strepsirrhini, strepsirrhines, which include lemurs, galagos, and Lorisidae, lorisids; and the Haplorhini, haplorhines, which include Tarsiiformes, tarsiers a ...
s – the first primate/proto-primate, ''
Purgatorius'', originated in the
Early Paleocene
The Danian is the oldest age (geology), age or lowest stage (stratigraphy), stage of the Paleocene Epoch or series (stratigraphy), Series, of the Paleogene Period or system (stratigraphy), System, and of the Cenozoic Era or Erathem. The beginnin ...
of the Nearctic.
* Family
Canidae
Canidae (; from Latin, ''canis'', "dog") is a family (biology), biological family of caniform carnivorans, constituting a clade. A member of this family is also called a canid (). The family includes three subfamily, subfamilies: the Caninae, a ...
–
dogs,
wolves,
foxes, and
coyotes.
* Family
Camelidae –
camels and their South American relatives including the
llama
The llama (; or ) (''Lama glama'') is a domesticated South American camelid, widely used as a List of meat animals, meat and pack animal by Inca empire, Andean cultures since the pre-Columbian era.
Llamas are social animals and live with ...
. Now extinct in the Nearctic
* Family
Equidae –
horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...
s,
donkey
The donkey or ass is a domesticated equine. It derives from the African wild ass, ''Equus africanus'', and may be classified either as a subspecies thereof, ''Equus africanus asinus'', or as a separate species, ''Equus asinus''. It was domes ...
s and their relatives. Now only found in the Nearctic as feral horses.
* Family
Tapiridae –
tapirs now extinct in the Nearctic.
* Family
Antilocapridae – last survivor of which is the
pronghorn.
* Subfamily
Tremarctinae (short-faced
bear
Bears are carnivoran mammals of the family (biology), family Ursidae (). They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats ...
s) – including the giant short-faced bear (''
Arctodus simus''). The only surviving member of the group is the
spectacled bear (''Tremarctos ornatus'') of South America.
Flora and fauna endemic to the Nearctic
Two
mammal
A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
families are endemic to the Nearctic, the pronghorns (
Antilocapridae) and the mountain beaver (
Aplodontiidae).
The Holarctic has four endemic families of birds:
divers (Gaviidae),
grouse (Tetraoninae),
auk
Auks or alcids are birds of the family Alcidae in the order Charadriiformes. The alcid family includes the Uria, murres, guillemots, Aethia, auklets, puffins, and Brachyramphus, murrelets. The family contains 25 extant or recently extinct speci ...
s (Alcidae), and the
waxwings (Bombycillidae). The scarab beetle families
Pleocomidae and
Diphyllostomatidae (
Coleoptera) are also endemic to the Nearctic. The fly species ''
Cynomya cadaverina'' is also found in high numbers in this area.
Plant families endemic or nearly endemic to the Nearctic include the
Crossosomataceae,
Simmondsiaceae, and
Limnanthaceae.
Nearctic terrestrial ecoregions
See also
*
List of ecoregions in Canada (WWF)
*
List of ecoregions in Mexico (WWF)
*
List of ecoregions in the United States (WWF)
References
* Abell, R.A. et al. (2000). ''Freshwater Ecoregions of North America: A Conservation Assessment'' Washington, DC: Island Press
Freshwater Ecoregions of North America: A Conservation Assessment
* Flannery, Tim (2001). ''The Eternal Frontier: an Ecological History of North America and its Peoples''. Grove Press, New York.
* Ricketts, Taylor H., Eric Dinerstein, David M. Olson, Colby J. Loucks, et al. (1999). ''Terrestrial Ecoregions of North America: a Conservation Assessment''. Island Press, Washington DC.
Terrestrial Ecoregions of North America: A Conservation Assessment
External links
Map of the ecozonesNearctica, The Natural World of North America*
{{Authority control
Biogeographic realms