Nearctic realm

The Nearctic realm is one of the eight biogeographic realms that make up Earth's land surface. It covers most of North America, including places like Greenland, Central Florida, and the highlands of Mexico.

The Nearctic realm is important because it includes many different kinds of plants and animals that live in forests, mountains, and other landscapes. Some areas of North America, such as southern Mexico, southern Florida, Central America, Bermuda, and the Caribbean islands, are not part of the Nearctic realm. Instead, these areas belong to the Neotropical realm along with South America.

Major ecological regions

The World Wildlife Fund splits the Nearctic realm into four main areas called bioregions. These areas group together similar natural environments that share many plants and animals.

The Canadian Shield bioregion stretches across the northern part of North America, from the Aleutian Islands to Newfoundland. It includes cold areas like arctic tundra and boreal forests.

The Eastern North America bioregion covers the eastern United States and southeastern Canada. It includes forests with many different types of trees, grassy plains, and some areas with coniferous trees, reaching down to central Florida.

The Western North America bioregion includes forests along the coast and in the mountains from southern Alaska through western Canada and the western U.S., stretching to the Rocky Mountains. It also has dry deserts and grasslands.

The Northern Mexico bioregion includes deserts, forests, and areas with a mix of pine and oak trees in parts of Mexico and the southwestern U.S. It is bordered by a different realm to the south.

History

Long ago, North America and South America were separated for about 180 million years. During this time, they developed different plants and animals. When the big landmass called Pangaea split apart, North America stayed connected to Eurasia as part of Laurasia, while South America became part of Gondwana.

Later, North America connected to both Asia and South America through land bridges. This allowed many plants and animals to travel between these areas, known as the Great American Interchange. A land bridge across the Bering Strait also let animals and plants move between Asia and North America. Because of this, the Nearctic realm shares many species with the Palearctic, and sometimes they are grouped together as the Holarctic realm.

At the end of the ice ages, during the Pleistocene epoch, many large animals like horses, camels, mammoths, and sabre-tooth cats (Smilodon) disappeared from North America. This was part of a big change called the Quaternary extinction event.

Flora and fauna

The Nearctic realm has many special animals and plants that first appeared there. Some mammals, like early primates, dogs, wolves, foxes, and coyotes, began here. Other animals such as camels, horses, tapirs, and short-faced bears also lived here, though some are no longer found in this area.

Some animal families are only in the Nearctic, like pronghorns and mountain beavers among mammals. There are also special birds like divers, grouse, auks, and waxwings. This region has unique scarab beetle families and fly species too. Plant families like Crossosomataceae, Simmondsiaceae, and Limnanthaceae are mainly found here.