Subarctic America covers most of Canada and Alaska. It is the northern section of the Nearctic realm with four subrealms as defined in the Bioregions 2023 framework—Greenland, Canadian Tundra, Canadian Boreal Forests, and Alaska—containing nine bioregions in total.

Northern America contains the majority of the Nearctic realm, spanning from southern Canada to northern Mexico and containing six subrealms as defined in the Bioregions 2023 framework—Northeast American Forests, Southeast US Savannas, Great Plains, American West, Mexican Drylands, and North Pacific Coast—containing 22 bioregions in total with a diversity of biome types.

Central America is the upper section of one of the Neotropical realms with two major subrealms—Central America and the Caribbean—containing six bioregions in total as defined in the Bioregions 2023 framework

Southern America covers most of the Neotropical realm with five major subrealms—Amazonia, Andes Mountains & Pacific Coast, South American Grasslands, Brazil Cerrado & Atlantic Coast, and Upper South America—with 23 bioregions in total as defined in the Bioregions 2023 framework.

The Afrotropics, or Sub-Saharan Africa, is one of the world’s major biogeographical realms with five major subrealm divisions based on the Bioregions 2020 framework -- Southern Afrotropics, Sub-Equatorial Afrotropics, Equatorial Afrotropics, Madagascar & East African Coast, and Sub-Saharan Afrotropics -- containing 24 bioregions in total.

Subarctic Eurasia covers most of the land mass of Russia and the Nordic countries – Iceland, Norway, Sweden, and Finland – and makes up the northern section of the Palearctic realm with four major subrealms as defined in the Bioregions 2020 framework -- Palearctic Tundra, Scandinavia & West Boreal Forests, Siberia & East Boreal Forests, and the Sea of Okhotsk.

Eastern Eurasia is the easternmost section of the Palearctic realm, divided into six major subrealms – East Asian Deserts, Tibetan Plateau, Mongolian Grasslands, Central East Asian Forests, Northeast Asian Forests, and Japanese Islands -- with 16 bioregions based on the Bioregions 2020 framework.

Central Eurasia makes up the interior section of the Palearctic realm with five major subrealms — Kazakh Steppes & Hemiboreal Forest, Caspian Sea & Central Asian Deserts, Tien Shan Mountains, Persian Deserts & Forests, and Altai-Sayan Mountains — containing 11 bioregions in total.

Western Eurasia covers most of Europe and is the westernmost section of the Palearctic realm with five major subrealms -- Greater European Forests, European Mountain Forests, Black Sea Forests & Steppe, the Mediterranean, and the British Isles -- and 13 bioregions in total as defined in the Bioregions 2020 framework.

Southern Eurasia corresponds roughly with the Middle East-North Africa (MENA) region and is the southernmost section of the Palearctic with two major subrealms -- North Africa and the Greater Arabian Peninsula – and five bioregions in total as defined by the Bioregions 2020 framework.

Indomalaya is one of the world’s eight major biogeographical realms with 3 major subrealms -- the Indian Subcontinent, Southeast Asian Forests, and Malaysia & Western Indonesia -- with 18 bioregions in total based on the Bioregions 2020 framework.

The Australasia realm is dominated by the Australian continent and two additional subrealms -- New Zealand and the Australasian Islands -- with 15 bioregions in total as defined in the Bioregions 2020 framework.

Antarctica, one of the world’s eight major biogeographical realms, is made up almost entirely of one single bioregion -- the ice-covered land mass, coastal tundra, and sea ice of the main continent -- which is nearly twice the size of Australia.

Oceania is one of the world’s major biogeographical realms with 11 island bioregions stretching across the Pacific Ocean, including Polynesia, Micronesia, and Hawaii.