Subarctic America covers most of Canada and Alaska and is the northern section of one of the world’s eight major biogeographical realms – the Nearctic – containing 9 bioregions in total.

Northern America is the lower section of one of the world’s eight major biogeographical realms – the Nearctic – which spans from southern Canada to northern Mexico.

Central America is the upper section of one of the world’s eight major biogeographical realms – the Neotropical – with 6 bioregions in total.

Southern America covers most of the Neotropical realm -- one of the world’s eight major biogeographical realms – with 23 bioregions in total.

The Afrotropics, corresponding roughly with Sub-Saharan Africa, make up one of the world’s eight major biogeographical realms and contain 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 one of the world’s eight major biogeographical realms – the Palearctic – containing 8 bioregions in total.

Eastern Eurasia is the easternmost section of the Palearctic -- one of the world’s eight major biogeographical realms – with 17 bioregions in total.

Central Eurasia is the interior section of the Palearctic -- one of the world’s eight major biogeographical realms – with 8 bioregions in total.

Western Eurasia covers most of Europe and is the westernmost section of the Palearctic -- one of the world’s eight major biogeographical realms – with 13 bioregions in total.

Southern Eurasia corresponds roughly with the Middle East-North Africa (MENA) region and is the southernmost section of the Palearctic -- one of the world’s eight major biogeographical realms – with 5 bioregions in total.

The Indomalayan realm is one of the world’s eight major biogeographical realms, with 18 bioregions in total.

The Australian continent dominates this realm -- one of the world’s eight major biogeographical realms -- with 15 bioregions in total.

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 eight major biogeographical realms with 11 island bioregions spanning across the Pacific Ocean, including Polynesia, Micronesia, and Hawaii.