Nearctic realm

The Nearctic is one of the eight major biogeographic regions of the Earth.

It includes almost all of North America, Greenland and the highlands of Mexico. On the other hand, southern Mexico, southern Florida, Central America and the Caribbean islands, together with South America, belong to the Neotropics.

North and South America, which are now connected at the Isthmus of Panama, were separated about 180 million years ago and thus evolved very different kinds of plants and animals. When the supercontinent Pangaea broke apart, North America remained connected to Eurasia and thus became part of the newly formed northern supercontinent Laurasia, while South America became part of the southern supercontinent Gondwana. The opening of the Atlantic Ocean separated North America and Europe.

North America was later connected by land bridges with Asia (Beringia) and South America (Isthmus of Panama). This allowed an exchange of species between the continents, the so-called Great American Interchange.

As a result, the Nearctic and the Palaearctic share a large number of animal and plant species. The two biogeographical regions are therefore also linked to form a common Holarctic region.

Many large animals, e.g. horses, camels, mammoths, mastodons, early bison, sabre-toothed tigers and short-nosed bears, became extinct at the end of the last ice age in the course of the Quaternary extinction wave with the simultaneous settlement by humans. Scientists believe that extinctions caused by human hunting, or the resulting shortage of food for predators, rather than climate change, caused the extinction of species.

Along with humans, however, the modern American bison, grizzly bear, and wapiti have been able to gain a foothold by vacating ecological niches.

Originally, the dogs (Canidae), the camels (Camelidae) and the horses (Equidae) only occurred in the Nearctic. The cloven-hoofed family of the pronghorns (Antilocapridae) always remained restricted to this region.

The cheetah originally evolved in North America and first came to Asia and later to Europe and today is still found mainly in Africa. The short-nosed bears also only lived in North America. The only surviving species of this family is the spectacled bear, which still lives in South America today.