The New International Encyclopædia/Nearctic Region
NEARCTIC REGION (from Gk. νέος, neos, new + ἀρκτικός, arktikos, arctic, northern). A region in zoögeography including the entire continent of North America, except the hot coast-lands of Mexico. It is a part of Arctogæa, or the Holarctic Region, in the view of those who regard the Northern Hemisphere as a unit in zoögeography; but in the scheme of Sclater and Wallace it is one of the six primary regions, coördinate with the Palearctic Province. (See Distribution of Animals, Zoögeographical Map.) Of further interest here are the subdivisions or local faunal areas that have been distinguished. The earliest attempt at this set apart three regions—an ‘Eastern,’ from the Atlantic to the plains; a ‘Central,’ including the dry interior plains; and a ‘Western,’ the Pacific Slope. As early as 1854 Louis Agassiz stated that the eastern half of the continent contained three faunas: a northern, which he called ‘Canadian;’ a middle (Great Lakes to the latitude of Kentucky), which he called ‘Alleghanian;’ and a southern or ‘Louisianian.’ Later writers, especially Allen, dealing mainly with birds, made eight zones in succession from north to south—Arctic, Hudsonian, Canadian, Alleghanian, Carolinian, Louisianian, Floridian, and Antillean. Ornithologists still use this classification east of the Mississippi River. Subsequently Merriam announced the opinion that there was no reason for recognizing a ‘Central Province,’ and that too much stress had been laid upon the dissimilarities between Eastern and Western animals. He asserted the view that only two primary subdivisions of the Nearctic Region should be made—a ‘Boreal’ province and a ‘Sonoran’ province. The former stretches from New England and the Great Lakes northwest across Canada to Alaska, and sends down long arms along the heights of the Alleghanies and the Rocky Mountains, and along the Pacific Coast, whose fauna is a mingled one. Everything south of this is ‘Sonoran,’ embracing nearly all the United States, a great area of the plains of Northwestern Canada, and all of Mexico except the low tropical coast-lands. These generalizations, however, have not been universally accepted, most critics objecting that too high rank has been accorded to the ‘Sonoran’ region, whose boundaries are regarded as too indefinite to entitle it to be differentiated and outlined as Merriam proposed in his “Biological Survey of the San Francisco Mountain Region,” in North American Fauna, No. 3 (Washington, 1890). The question of the subdivision of the Nearctic Region therefore remains open.