- Nearctic ecozone
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For the thoroughbred racehorse, see Nearctic (horse).
The Nearctic is one of the eight terrestrial ecozones dividing the Earth's land surface.
The Nearctic Ecozone
The Nearctic ecozone covers most of North America, including Greenland and the highlands of Mexico. Southern Mexico, southern Florida, Central America, and the Caribbean islands are part of the Neotropic ecozone, together with South America.
Contents
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 temperate grasslands of the central United States and south-central Canada, and the Temperate coniferous forests of the southeastern United States.
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 to the Rocky Mountains, as well as the cold-winter intermountain deserts and xeric shrublands 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 and Southwestern North America
The Northern Mexico bioregion includes the mild-winter to cold-winter deserts and xeric shrublands of northern Mexico, Southern California, and the Southwestern United States, including the Chihuahuan, Sonoran, and Mojave deserts. The Mediterranean climate ecoregions of the Southern and Central Coast of California include the California chaparral and woodlands, California coastal sage and chaparral, California interior chaparral and woodlands, and California montane chaparral and woodlands.
The bioregion also includes the warm temperate and subtropical pine and pine-oak forests, including the Arizona Mountains forests and the Sierra Madre Occidental, Sierra Madre Oriental, and Sierra Juarez and San Pedro Martir pine-oak forests.
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 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 and South America since then, which allowed an exchange of plant and animal species 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 ecozone shares many plants and animals with the Palearctic. The two ecozones are sometimes included in a single Holarctic ecozone.
Many large animals, or megafauna, including horses, camels, mammoths, mastodonts, ground sloths, sabre-tooth cats (Smilodon), the giant short-faced bear (Arctodus simus), and the cheetah, became extinct in North America at the end of the Pleistocene epoch (ice ages), at the same time the first evidence of humans appeared, in what is called the Holocene extinction event. Previously, it was believed that the megafaunal extinctions were caused by the changing climate, but many scientists now believe that while the climate change contributed to these extinctions, the primary cause was hunting by newly-arrived humans or, in the case of some large predators, extinction resulting from prey becoming scarce. The American bison (Bison bison), brown bear or grizzly bear (Ursus arctos), and elk or wapiti (Cervus canadensis) entered North America around the same time as the first humans, and expanded rapidly, filling ecological niches left empty by the newly-extinct North American megafauna.
Flora and fauna
Flora and fauna that originated in the Nearctic
Animals originally unique to the Nearctic include:
- Family Canidae, dogs, wolves, foxes, and coyotes
- Family Camelidae, camels and their South American relatives including the llama. The last North American Camelids went extinct during the last ice age.
- Family Equidae, horses and their relatives.
- Family Antilocapridae, which includes the pronghorn
- Tremarctinae, or short-faced, bears, including the extinct giant short-faced bear (Arctodus simius). The last remaining member of the group is the spectacled bear (Tremarctos ornatus) of South America.
- The now-extinct American cheetah (Miracinonyx)
Flora and fauna endemic to the Nearctic
One bird family, the wrentits (Timaliinae), is endemic to the Nearctic region. The Holarctic has four endemic families: divers (Gaviidae), grouse (Tetraoninae), auks (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.
Plants families endemic or nearly endemic to the Nearctic include Crossosomataceae, Simmondsiaceae, and Limnanthaceae.
Nearctic Terrestrial Ecoregions
Sierra Madre Occidental pine-oak forests Mexico, United States Sierra Madre Oriental pine-oak forests Mexico, United States Nearctic Temperate broadleaf and mixed forestsUnited States Appalachian mixed mesophytic forests United States Appalachian-Blue Ridge forests United States California mixed evergreen forest United States Central U.S. hardwood forests United States East Central Texas forests United States Eastern forest-boreal transition Canada, United States Eastern Great Lakes lowland forests Canada, United States Gulf of St. Lawrence lowland forests Canada Lac Saint-Jean and Saguenay valley forests Canada Mississippi lowland forests United States New England-Acadian forests Canada, United States Northeastern coastal forests United States Ozark Mountain forests United States Southeastern mixed forests United States Southern Great Lakes forests United States Upper Midwest forest-savanna transition United States Western Great Lakes forests Canada, United States Willamette Valley forests United States Nearctic Temperate coniferous forestsCanada Alberta-British Columbia foothills forests Canada Arizona Mountains forests United States Atlantic coastal pine barrens United States Blue Mountains forests United States British Columbia mainland coastal forests Canada, United States Cascade Mountains leeward forests Canada, United States Central and Southern Cascades forests United States Central British Columbia Mountain forests Canada Central Mexican Volcanoes forests Mexico Central Pacific coastal forests Canada, United States Colorado Rockies forests United States Eastern Cascades forests Canada, United States Fraser Plateau and Basin complex Canada Great Basin montane forests United States Klamath-Siskiyou forests United States Maritime Coast Range Ponderosa Pine forests United States Middle Atlantic coastal forests United States North Central Rockies forests Canada, United States Northern California coastal forests United States Northern Pacific coastal forests Canada, United States Northern transitional alpine forests Canada Okanogan dry forests Canada, United States Piney Woods forests United States Puget lowland forests Canada, United States Queen Charlotte Islands Canada Sierra Juarez and San Pedro Martir pine-oak forests Mexico Sierra Nevada forests United States South Central Rockies forests United States Southeastern conifer forests United States Wasatch and Uinta montane forests United States Nearctic Boreal forests/taigaUnited States Central Canadian Shield forests Canada, United States Cook Inlet taiga United States Copper Plateau taiga United States Eastern Canadian forests Canada Eastern Canadian Shield taiga Canada Interior Alaska-Yukon lowland taiga Canada, United States Mid-Continental Canadian forests Canada Midwestern Canadian Shield forests Canada, United States Muskwa-Slave Lake forests Canada Newfoundland Highland forests Canada Northern Canadian Shield taiga Canada Northern Cordillera forests Canada Northwest Territories taiga Canada South Avalon-Burin oceanic barrens Canada Southern Hudson Bay taiga Canada Yukon Interior dry forests Canada Eastern savannas of the United States (greatly declined) United States Central Hardwood Region (greatly declined) United States Western Gulf coastal grasslands Mexico, United States Canadian aspen forests and parklands Canada, United States Central and Southern mixed grasslands United States Central forest-grasslands transition United States Central tall grasslands United States Columbia Plateau United States Edwards Plateau savanna United States Flint Hills tall grasslands United States Montana valley and foothill grasslands United States Nebraska Sand Hills mixed grasslands United States Northern mixed grasslands Canada, United States Northern short grasslands Canada, United States Northern tall grasslands Canada, United States Palouse grasslands United States Texas blackland prairies United States Western short grasslands United States Nearctic TundraCanada, United States Aleutian Islands tundra United States Arctic coastal tundra Canada, United States Arctic foothills tundra Canada, United States Baffin coastal tundra Canada Beringia lowland tundra United States Beringia upland tundra United States Brooks-British Range tundra Canada, United States Davis Highlands tundra Canada High Arctic tundra Canada Interior Yukon-Alaska alpine tundra Canada, United States Kalaallit Nunaat high arctic tundra Greenland Kalaallit Nunaat low arctic tundra Greenland Low Arctic tundra Canada Middle Arctic tundra Canada Ogilvie-MacKenzie alpine tundra Canada, United States Pacific Coastal Mountain icefields and tundra Canada, United States Torngat Mountain tundra Canada California interior chaparral and woodlands United States California montane chaparral and woodlands United States Nearctic Deserts and xeric shrublandsMexico Central Mexican matorral Mexico Chihuahuan desert Mexico, United States Colorado Plateau shrublands United States Great Basin shrub steppe United States Gulf of California xeric scrub Mexico Meseta Central matorral Mexico Mojave desert United States Okanagan (South) shrub steppe Canada Snake-Columbia shrub steppe United States Sonoran desert Mexico, United States Tamaulipan matorral Mexico Tamaulipan mezquital Mexico Wyoming Basin shrub steppe United States Biomes and Ecozones Terrestrial
biomesPolar/montaneTemperate(Sub)tropicalDryWetAquatic
biomesOther biomes Ecozones External links
Media related to Nearctic at Wikimedia Commons- Map of the ecozones
- Nearctica, The Natural World of North America
References
- 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.
Categories:- Nearctic
- Nearctic flora
- Ecozones
- Natural history of North America
- Biogeography
- Phytogeography
- Flora of the Western United States
- Flora of California
- Flora of the Southwestern United States
- Flora of the Plains-Midwest (United States)
- Flora of the Northern United States
- Flora of the Eastern United States
- Flora of Canada
- Flora of Greenland
- Flora of Mexico
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